Protein Intake & IGF-1 Production

Protein Intake & IGF-1 Production
4.58 (91.5%) 40 votes

Animal protein consumption triggers the release of the cancer-promoting growth hormone IGF-1.


What is the mechanism by which our diet can affect our levels of this cancer-promoting growth hormone IGF-1? Imagine you’re a kid with some Tinkertoys. Then, Christmas comes early, and you get one of those huge sets dumped down in front of you. All excited with this new load of building raw materials, you may really start scaling up. And basically, it’s the same thing with your liver and insulin-like growth factor 1.

When you dump a load of protein on your body, your liver’s like whoa, look at all this. What are we going to do with all? We can’t just waste it; we’ve got to do something with it. Let’s just start growing stuff; add a few new additions, maybe a new wing. So your liver decides to start pumping out IGF-1 to tell all the cells in the body, it’s growin’ time! Be fruitful and multiply. Spare no expense, go crazy—look how much excess protein we got to work with!

The problem, of course, is that some of the new additions may be tumors. When you’re a fully grown adult, cell growth is something we want to slow down—not accelerate. So one might imagine the goal would be to maintain adequate, but non-excessive, overall protein intake—but wait a second.

Studies have found no association between total protein intake and IGF-1 levels. Doesn’t that just go against everything I just said? Ah, but these studies didn’t take into account animal versus plant protein.

In this study of meat-eaters, vegetarians, and vegans, they found no significant difference in IGF levels between people eating lots of protein, compared to people eating less protein. But before ditching the theory that excessive protein intake boosts the levels of IGF-1, they decided to break it down into animal protein versus plant protein.

Higher IGF-1 levels were just associated with animal protein intake. In fact, the plant protein seemed to decrease IGF-1 levels. So, no wonder there was no net effect of total protein intake. Animal protein appears to send a much different signal to our livers than most plant proteins. So even those vegans eating the same amount of protein as meat-eaters still had lower levels of the cancer-promoting hormone, IGF-1.

So, it’s apparently not about excessive protein in general, but animal protein in particular. And I’ll try to explain why tomorrow.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by Kerry Skinner.

Please consider volunteering to help out on the site.

Images thanks to: ttrentham, danmachold, and Tinker*Tailor loves Lalka via flickr. Images have been modified.

What is the mechanism by which our diet can affect our levels of this cancer-promoting growth hormone IGF-1? Imagine you’re a kid with some Tinkertoys. Then, Christmas comes early, and you get one of those huge sets dumped down in front of you. All excited with this new load of building raw materials, you may really start scaling up. And basically, it’s the same thing with your liver and insulin-like growth factor 1.

When you dump a load of protein on your body, your liver’s like whoa, look at all this. What are we going to do with all? We can’t just waste it; we’ve got to do something with it. Let’s just start growing stuff; add a few new additions, maybe a new wing. So your liver decides to start pumping out IGF-1 to tell all the cells in the body, it’s growin’ time! Be fruitful and multiply. Spare no expense, go crazy—look how much excess protein we got to work with!

The problem, of course, is that some of the new additions may be tumors. When you’re a fully grown adult, cell growth is something we want to slow down—not accelerate. So one might imagine the goal would be to maintain adequate, but non-excessive, overall protein intake—but wait a second.

Studies have found no association between total protein intake and IGF-1 levels. Doesn’t that just go against everything I just said? Ah, but these studies didn’t take into account animal versus plant protein.

In this study of meat-eaters, vegetarians, and vegans, they found no significant difference in IGF levels between people eating lots of protein, compared to people eating less protein. But before ditching the theory that excessive protein intake boosts the levels of IGF-1, they decided to break it down into animal protein versus plant protein.

Higher IGF-1 levels were just associated with animal protein intake. In fact, the plant protein seemed to decrease IGF-1 levels. So, no wonder there was no net effect of total protein intake. Animal protein appears to send a much different signal to our livers than most plant proteins. So even those vegans eating the same amount of protein as meat-eaters still had lower levels of the cancer-promoting hormone, IGF-1.

So, it’s apparently not about excessive protein in general, but animal protein in particular. And I’ll try to explain why tomorrow.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by Kerry Skinner.

Please consider volunteering to help out on the site.

Images thanks to: ttrentham, danmachold, and Tinker*Tailor loves Lalka via flickr. Images have been modified.

Doctor's Note

For background on IGF-1, see IGF-1 as One-Stop Cancer Shop and Cancer-Proofing Mutation. In The Answer to the Pritikin Puzzle, we established that the reason the blood of those eating plant-based diets appeared so much better at fighting cancer cell growth (see Ex Vivo Cancer Proliferation Bioassay) is likely due to the drop in IGF-1 levels, especially in those following vegan diets (see How Plant-Based to Lower IGF-1?).  Now it appears we know why—their avoidance of animal protein. Let’s go one level deeper, and ask why animal protein preferentially triggers IGF-1 release. Stay tuned for my next video, Higher Quality May Mean Higher Risk.

For further context, be sure to check out my associated blog post: Animal Protein and the Cancer Promoter IGF-1.

If you haven’t yet, you can subscribe to my videos for free by clicking here.

130 responses to “Protein Intake & IGF-1 Production

Comment Etiquette

On, you'll find a vibrant community of nutrition enthusiasts, health professionals, and many knowledgeable users seeking to discover the healthiest diet to eat for themselves and their families. As always, our goal is to foster conversations that are insightful, engaging, and most of all, helpful – from the nutrition beginners to the experts in our community.

To do this we need your help, so here are some basic guidelines to get you started.

The Short List

To help maintain and foster a welcoming atmosphere in our comments, please refrain from rude comments, name-calling, and responding to posts that break the rules (see our full Community Guidelines for more details). We will remove any posts in violation of our rules when we see it, which will, unfortunately, include any nicer comments that may have been made in response.

Be respectful and help out our staff and volunteer health supporters by actively not replying to comments that are breaking the rules. Instead, please flag or report them by submitting a ticket to our help desk. is made up of an incredible staff and many dedicated volunteers that work hard to ensure that the comments section runs smoothly and we spend a great deal of time reading comments from our community members.

Have a correction or suggestion for video or blog? Please contact us to let us know. Submitting a correction this way will result in a quicker fix than commenting on a thread with a suggestion or correction.

View the Full Community Guidelines

  1. For background on IGF-1 see IGF-1 as One-Stop Cancer Shop and Cancer-Proofing Mutation. In The Answer to the Pritikin Puzzle we established that the reason the blood of those eating plant-based diets appeared so much better at fighting cancer cell growth (see Developing an Ex Vivo Cancer Proliferation Bioassay) is likely due to the drop in IGF-1 levels, especially those following vegan diets (as per the last video-of-the-day How Plant-Based to Lower IGF-1?).  Now it appears we know why—their avoidance of animal protein. Let’s go one level deeper and ask why animal protein preferentially triggers IGF-1 release. Stay tuned for tomorrow’s video-of-the-day Higher Quality May Mean Higher Risk.

    If you haven’t yet, you can subscribe to my videos for free by clicking here.

    1.  While the Allen et al study found association between animal protein intake and IGF1 levels, it did not try to check different types of animal proteins. Therefore, the association may be only due to dairy protein and not other types of animal protein. In other studies that checked different types of animal proteins, meat and egg proteins were not associated with IGF1 levels.

  2. What implications does this have for those looking to gain weight (muscle)? The benefits of huge amounts of protein, especially animal protein are often publicized by the whey protein, lean chicken brigade. But do they have a point? The data I am aware of is that animal protein is indeed of extra benefit in terms of muscle gain, strength. Is it possible that extra protein consumption does indeed stimulate IGF-1 which in turns signals cells all over the body to grow. But because there is exercise induced stimulus, the IGF-1 stimulates muscle growth as opposed to tumor growth etc. * Disclaimer: I do exercise but I also eat a plant based diet and am convinced of the overall vast superiority of plant based vs. carnivorous, regardless of the muscle growth implications! 

    1.  Conor:  I think you have an interesting question.  I don’t know if we have a scientific answer or not.  But I wanted to share this:  Brenda Davis has a great slide show on designing an optimum plant-based diet (ie, one that is nutritionally adequate as well as ideal for preventing diseases).  One of her slides is a very impressive picture of “Alexander Dargatz – Vegan – World Bodybuilding Champion (2005)”.  That’s just an anecdotal case, but his muscles are pretty big…

      Also, I think the following part of your inquiry is not supported by anything I have heard: ” But because there is exercise induced stimulus, the IGF-1 stimulates muscle growth as opposed to tumor growth etc.”  It may (or may not) stimulate muscle growth in addition to tumors, but *instead of*?  My understanding of the studies (which may be incorrect) is that the problem with the IGF-1 is that it doesn’t make that distinction once we pass our normal growth phases.

      Thanks for this interesting question.

    2. I wonder the same thing with implications for childrens’ growth.  I’ve got two kids that eat mostly vegan.  We’re all short and I’d like to get as much growth as possible from these kids of mine.  Am I limiting possible growth by not giving them animal products?

      1. Stacy:  That’s just so interesting to me.  I wonder why you want to “get as much growth as possible”?  It’s my understanding (perhaps incorrectly) that smaller people live longer as a general rule. 

        For me, I want my kids to grow exactly as much as is healthy for them.  No more, no less.  (FYI: My family is pretty short too, but within “normal” ranges.)

        Hypothetical: Suppose I could get my kids to grow 1 (2, 3, 4?) inches bigger because I fed them meat and dairy.  I doubt that is even possible, but suppose it is.  With all that meat and dairy intake, they could/likely end up with the diseases associated with meat and dairy intake.  I would not consider that to be a good trade-off.

        I mean absolutely no disrespect and you certainly do not have to explain yourself to me/on this site.  I’m just really curious why you would see maximizing growth in a child just for the sake of growth as being a good thing.

        FYI: I consider the “Vegetarian Resource Group” to be a quality source of information.  Here is one paragraph from their page on the topic of height and vegan children:

        “While some studies show that vegan children are at a lower percentile of
        weight and
        height than are other children of a similar age, a recent study shows
        that vegan
        children can have growth rates which do not differ from those of
        omnivorous children
        of the same age (10). At this time we cannot say that a child growing
        at the 25th
        percentile is any more or less healthy than a child growing at the 75th
        What seems to be more important is that the child stays at about the
        same percentile.
        For example, a child who is at the 50th percentile for height at age 2
        and only at the
        25th percentile at age 3 has had a faltering in growth rate. The cause
        of this faltering
        should be determined. In addition, children at extremes (5th percentile
        or lower or 85th percentile or higher) should be individually assessed
        by their health care provider.”

        1.  I thought I should also add a link to the excellent page on raising vegan children and also include this paragraph:

          “The best way to assure that your children achieve their ideal rate of growth is to make
          sure that they have adequate calories. Some vegan children have difficulty getting
          enough calories because of the sheer bulk of their diets. Children have small
          stomachs and can become full before they have eaten enough food to sustain growth.
          The judicious use of fats in forms like avocados, nuts, nut butters, seeds, and
          seed butters will provide a concentrated source of calories needed by many vegan
          children. Dried fruits are also a concentrated calorie source and are an attractive
          food for many children. Teeth should be brushed after eating dried fruits to prevent
          tooth decay.”

        2. The reason I want to get as much growth as possible from my kids is because they are incredibly small.  I try to take comfort that my kids are very healthy and they are on their way to long healthy lives.  I simply can’t ignore the pain my son (my daughter loves being small) deals with being as small as he is.  He is 12 and he is the size of a typical 8-9 year old.  This is very hard on a boy and, frankly, short men don’t have it easy.  I’m only 5 ft tall so I know eating meat every day as a child does not equal average or more height.  But if I deprive my son of an extra inch or two I would feel terrible.  Yes, I think those few inches would mean an awful lot to him as there is a world of difference in the experience of a man who is 5′ 8″ than a man who is 5′ 6″.  And a piece of meat every now and then isn’t going to give him cancer.  (This is crazy coming from vegan me!!  I’m very anti-animal products but this type of study makes me wonder if I’m making my son suffer needlessly.)

          I wish I hadn’t phrased my question as I did because I don’t want to come off as some typical person who just wants to be really tall or have my kids be really tall.  NOT AT ALL.  They really are crazy short and at some point I would take a little health risk to minimize the risk to my son’s MENTAL health.  And I really do want to know – should I expect my children to grow less on a vegan diet?  It seems like the answer is yes.

          1.  Stacy:  Clearly you are a caring, loving parent.  I can understand where you are coming from.

            re: “It seems like the answer is yes.”
            I still do not pick that up from what I have been reading.  Your question so interested me that I kept doing some research on line.  I don’t know how credible this site is, but you might want to read this:

            Also, as anecdotes, I have seen young adults who where raised all their lives as vegan and they were taller than me…

            I don’t know the real answer, but I wonder if anyone does right now?

            Whatever you decide, best of luck to you and your kids!!!

          2.  Stacy, I feel for you son. I was always the shortest in my class when I was growing up, and I was hurt by the rejection by other boys- no one wanting me on their sports team, getting beat up by bullies as an easy target, things like that. Some of the emotional scars last to this day. I’m still shy, hate competitive sports, don’t compete with anyone but myself and don’t really relate to most other men. Yet, I wouldn’t want to be taller because it’s true that shorter people live longer and good health is more important than popularity. In addition, I think I have more compassion and am gentler than most men- things that I value. As a practical matter, let me suggest that your boy wear elevator shoes. They even make tennis shoes that increase height now.

          3. I ate a typical American diet (which is better than today’s typical) My mother made meals at home but often the vegetables were overcooked, etc. I became a vegetarian in 11th grade. When I was 26, I suffered an injury that caused fibromyalgia and I began juicing and taking whole food supplements. I grew 1.5 inches. I could not believe it but found out that it is possible to gain height until about age 27. So, it was not the lack of protein, it was the lack of bioavailable and adequate micronutrients.

          4. Mrs Thea is obviously a loony, unfeeling fanatic. Don’t listen to her. Your kids wouldn’t be too grateful to you, if you told them that you had willingly fed them with inferior nutrition, and that they will healthily live up to 100 years in solitude, because they are small.

            The consumption of vegetal food is always accompanied by severe undernutrition. In order to support the growth of your children, you must increase the consumption of milk products, pork meat and fish, and decrease the consumption of cereals to a minimum. If you are afraid of health consequences, then concentrate only on whole milk, yoghurt, curd, low-fat cheese and fish. You can also pick up some good vegetal products like spinage and soy, but other vegetables are only slightly better than cereals. Further, buy some calcium supplement and give your son high doses over 1 g/day. Alternatively, you can consult it with a doctor and apply human growth hormone (HGH). Remember that you don’t have much time. The growth in some people can finish at the age of 16-17 years.

            1. Do you have clinical references to support your statements?

              I would offer the following for starters:


              It is the position of the American Dietetic Association that appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases. Well-planned vegetarian diets are appropriate for individuals during all stages of the life cycle, including pregnancy, lactation, infancy, childhood, and adolescence, and for athletes.


        3. “It’s my understanding (perhaps incorrectly) that smaller people live longer as a general rule.”
          The Japanese are smaller people, but eat all kinds of animal proteins and still outlive most populations on the planet. They also have far, far lower cancer rates while still eating animal proteins. Of course they also eat far more healthy vegetables and seed weed that contains large amounts of iodine.

          On the other hand, the Masai tribe of East Africa that are among the tallest people in the world eat a diet mainly of animal proteins and even blood, with very little plant based foods, but have an almost non-existent cancer rate.

          It’s bad science to reduce cancer rates to merely the consumption of animal proteins per- se. Here in America, we need to examine the quality of the animal proteins being consumed. If we take populations that consume commercially produced animal proteins, which have been produced with the use of artificial hormones (BGH), antibiotics, and fed GMO feed, then of course, there will be higher cancer rates. But consider the time just 50 years ago when mostly everyone ate meat regularly in abundance in the US that the cardio-vascular diseases, cancer, and diabetes rates were far lower than today.

          It’s not just eating animal proteins. It’s WHAT’S BEEN DONE to the meats Americans eat before they get to the table. Has there been any studies comparing those eating only organically produced meats and poultry, and only wild caught fish with vegetarians and vegans?

            1. You couldn’t be more wrong. The Massai are very tall.

              “In the case of some Sudanese tribes, males can have an average height of 1.9 m (6 ft, 4in) (!), while women of 1.8 m (6 ft) (!). These people have slim but strong bodies, and their heads are more elongated than in the case of the typical African Blacks. In case of a mixed race, these huge heights may not be generally attained by the population.

              The most famous group and more racially preserved of the Sudanese race are the Nilotic tribes (they all originated on the Upper Nile area). The most famous are Massai, Turkana, Samburu and Dinka, whose main occupation is animal husbandry.

              Read more:

    3. Conor,
      Billy Simmonds (2009 Mr Natural Universe) he is vegan. You can find some videos around the web on him. I signed up on his website but I haven’t seen anything useful on it but you can check it out. has some interesting and useful info as well.
      Here’s to pumping iron and plants, not pigs!

    4.  Conor,

      This is a great question and if someone using this site has an answer I’d love to know as well. 

      I will add that having switched to plant based diet with a plant derived protein powder supplement and my weight training has thrived. 

    5. Hi Conor: It may be true that protein supplementation improves muscle size. This doesn’t mean that it helps muscle function and it ignores the fact that animal foods and protein are harmful to our kidneys and arterial system in both the long and short run. It is nice to keep seeing science that supports our design as hind gut fermenting herbivores(plant eaters) who have evolved with a longer small intestine and more amylase genes(to digest starches) than great apes who are genetically our closest relatives. It is also a reasonable hypothesis that if we follow a plant based diet our only exposure to animal protein would be our mothers milk when we are rapidly growing important systems including our brain. So it makes sense to me animal protein would be designed to promote growth for our earliest years. The other reason that eating meat may help build muscle size is the use of androgenic steroids in meat see video.. This means that folks who are eating alot of meat are basically doping. Dr. Greger has posted over 100 videos on meat on his website. An example of a very successful endurance plant based athlete is Scott Jurek who wrote the book, Eat and Run, and was featured in the book, Born to Run. Congratulations on following a dietary path that should maximize your function-ability and minimize future disease as long as you insure adequate B12 intake (see video series in February of this year). Best wishes.

    6. Go check out Mike Mahler. He is one example of how to build muscle on plant foods.

      Probably dealing with hormone imbalances such as estrogen dominance is a far bigger factor than protein source when concerned with putting on muscle.

    7. There may be some correlation, but the majority of muscle growth is from myostatin deficiencies. Google people with myostatin deficiencies. Some people are just genetically gifted, and could eat bread and drink water and still get incredible gains. so sorry to the comment under mine, but one or two, or even ten bodybuilding vegan isn’t a case against this, and if were to test their DNA you would see little to no expression of the myostatin gene.

    8. Every single human will gain weight.. And muscle.. from a high animal fat protein diet..
      What’s being said in the main statement above is of the danger behind the scene..
      The damage you can’t see being done.. Until it’s too late.. Unless you’ve heard of dr Mcdougal! That starch solution is just a work of genius..!

  3. I’m a 70-something 120# neophyte vegan. I finished chemo for TNBC a year ago, and have regular follow-up blood tests (CBC, Basic Metabolic Panel & CA15-3 tumor marker).  I’ve gone from normal range, 6.2 total protein in March to 5.8 in June and 5.9 in Sept.  What is an adequate range of protein intake per day for a vegan? Is there a formula to estimate it?  (I’m a daily subscriber…)

    1. Hi Ruth, There is no need for a formula for adequate protein intake as long as you consume adequate calories. Dr. MacDougall did three excellent newsletters on Protein concerning history, sources and overload. You can go to his website look under newsletters and read the three articles. Newsletter dates are  12/03, 4/07 and 1/04. The variation in your protein levels is very small and not generally related to our protein intake. The Physicians Committee for Responsible Medicine has a pamphlet, Healthy Eating for Life, available for free download at Of course Dr. Greger has done many videos on cancer in general as well as specific cancers such as breast cancer so you want to keep referring to the site as questions arise. His Vitamin B12 series in February of this year is important. He has also done a series of You Tube video entitled, Stopping Cancer before it Starts. Of course, you want to stay tuned as the science keeps changing. Finally, patients need to work with their physicians as each individuals situation is unique. Congratulations on choosing a diet which will minimize your chances for future difficulties.Best wishes.

  4. Dr. Greger, 

    Thank you very much for your research and your website.  As a fellow physician, I have found this a great resource to getting research based information on healthy eating.

    As you accumulate more and more videos, you may want to create sections of small series of videos to explain things clearly.  For instance, this video on IGF-1 should likely fit into a package of 5-10 videos that together provide clear fact-based information on why animal protein is bad for you.

    Also, I would like to know why animal proteins and not plant based proteins stimulate IGF-1?  Is this due to oligopeptides acting as cell receptors, disulfide bonds, or do we know at this point?

    1.  I think Dr. Gregor’s Blog (Find it in the menu at the very top of the page), covers this very nicely.  The blogs link many videos (older and new) into a context sensitive tour through the videos.

  5. I really appreciate all of your videos; especially that you make them easy for the layman to understand! Never liking any kind of science or math, a nutrition professor of mine about a year ago got me so motivated about fitness and this website. Thank you to you and your team. 

  6. Does this mean that by taking a Soy Protein Isolate with a morning breakfast smoothie is harmful if animal protein is consumed during the day?

        1.  If you eat enough calories to survive, and eat only whole, plant based
          foods, you will get more than enough protein even if working out hard
          every day. Protein and caloric needs are equivalent. You will never not get enough protein. It is a pointless practice perpetuated by the supplement industry to count how much protein one is eating and to supplement it. The body has no storage mechanism for protein and it is used as needed.

          1. I am confused. My trainer has told me vegans have a harder time building muscle. would this be from eating low calorie foods, and hence having to eat a higher amount of volume to ensure enough calorie intake or is it because we do need to supplement protein. I guess what i’m asking is then whats more important for muscle building, enough/excess protein or enough/excess calories? excess of the body daily maintenance.

            1. Your trainer should show you some evidence of this because this is not true, vegans have 20% higher levels of circulating protein compared with omnivores

              Dr. Greger will soon cover a video comparing vegan body building compared with omnivorous body building and the result is that vegans can build just as much muscle.

              Perhaps with a raw foodist (one who consumes primarily raw greens and fruits) there may be an issue of not achieving an adequate caloric load but even so, with a raw foodist they quickly get hungry when eating this way as their body is demanding more calories so they end up eating a lot all day to make up for their low calorie diet.

              On the other hand as a normal whole foods plant based vegan, if you consume a filling meal of brown rice with other vegetables for example. and you stay satiated for a while, you are indeed getting enough calories.

              Like I mentioned before, it is a pointless practice to count calories when eating whole plant based foods. Energy expenditures and protein needs are equivalent.Furthermore, body builders tend to consume far excess protein, which is also not healthy. as a humans protein needs are fairly low.

              1.  Thank you Toxins, for your reply and explanation. I look forward to that vegan bodybuilding video as it may be the holy grail for those, trying to build muscle as vegans.

                why does everyone say you need protein to build muscle? would it not be possible to build the same amount of muscle on say carbs (given sufficient intake of calories)?

                I say carbs, as there as those that follow doug graham’s 80/10/10 diet and although they look trim and healthy, alot of them are endurance athletes as opposed to strength/muscle building athletes, and have the bodies to reflect that.

                Really appreciate your insight!

                1.  You are misunderstanding what I am saying, I am not trying to say that we do not need protein to build muscle but what I am saying is that we do not need to count protein or get an excess of it to get muscle. All whole plant foods contain complete proteins.

                  1.  ah ok i understand now. Eating sufficent calories from a whole food diet would automatically ensure adequate protein for muscle building. i understand now.

                    Thanks again Toxins!

                2.  In Addition, The anabolic phase is a critical phase occurring within 45 minutes
                  post-exercise. It is during this time that muscle cells are particularly
                  sensitive to insulin, making it necessary to ingest the proper
                  nutrients in order to make gains in muscle endurance and strength. If
                  the proper nutrients are ingested 2 – 4 hours post-exercise they will
                  not have the same effect. It is also during this time in which the
                  anabolic hormones begin working to repair the muscle and decrease its
                  inflammation. Immediate ingestion of carbohydrate is important
                  because insulin sensitivity causes the muscle cell membranes to be more
                  permeable to glucose within 45 minutes post-exercise. This results in
                  faster rates of glycogen storage and provides the body with enough
                  glucose to initiate the recovery process (Burke et al., 2003). Muscle
                  glycogen stores are replenished the fastest within the first hour after
                  exercise. Consuming carbohydrate within an hour after exercise also
                  helps to increase protein synthesis (Gibala, 2000).

                3. Hi Basskills,

                  Body builders build muscles because they lift weights. Runners are lean because they run. If runners started lifting weights (primarily) and weight lifters starting running you would see the change. It is called specificity of training.

              2. I can’t find the video you spoke of. If Dr.Gegor has not covered this topic in detail, please ask for me. Too many people take these whey and egg proteins.

                  1. You said vegan body builders get just as much muscle. That was not mentionned in Gregor’s videos. Now, since he’s mainly concerned with regular people, he did however talk about how “closer to perfect” proteins stimulate IGF-1 production. Still, IGF-1 and perfect proteins may in fact allow for increased mass in bodybuilding compared to those eating less perfect proteins. This is assuming both bodybuilders are eating carbs in their critical phases.

                    Whey protein and eggs whites are the most bio-available proteins out there. Eating those will cause the liver to secrete IGF-1, a hormone that promote cell division. I don’t see any mention of vegans eating less perfect proteins and getting the same results as omnivorous bodybuilders.

                    I am definitely removing perfect proteins from my diet because of increased IGF-1 production. I’m mainly concerned with the claims you made.

  7. The article cited was very interesting. In addition to high intakes of calories, protein rich in essential amino acids such as meat or soya, zinc was also
    associated with high levels of IGF-1. In fact, the article listed seven other studies that showed increased zinc was associated with increased IGF-1.  Bodybuilders often take zinc supplements in the form of a product called ZMA to build muscles, which implies that their IGF-1has increased. Dr. Greger did a video some time ago which said that vegans don’t always get sufficient zinc and that zinc from vegan sources is absorbed poorly. Perhaps this is the result of some cosmic benevolence and that there’s good reason for blood zinc levels to be low in health-conscious vegans.The RDA for zinc and other nutrients found in high levels in milk and meat are often set higher than necessary. Could it be that the department of Agriculture is influenced by big meat and big dairy to encourage us to eat those foods? I think that’s a pretty safe bet. 

    1. Could it be that the association between zinc and increased IGF-1 is due to the fact that animal foods are the best sources of zinc? Are there studies showing zinc consumption from supplements actually increases IGF-1 production ?

  8. This totally ignores the fact that whey protein concentrate is a glutathione precursor and glutathione – one of the most powerful antioxidants – is considered a major anti-cancer factor.
    seeCurr Pharm Des. 2007;13(8):813-28.
    A role for milk proteins and their peptides in cancer prevention.Anticancer Res. 2000 Nov-Dec;20(6C):4785-92.
    Whey protein concentrate (WPC) and glutathione modulation in cancer treatment.Anticancer Res. 2003 Mar-Apr;23(2B):1411-5.
    The antioxidant system.Cancer Lett. 1991 May 1;57(2):91-4.
    Whey proteins in cancer prevention.Cancer Epidemiol Biomarkers Prev. 2000 Jan;9(1):113-7.
    Diets containing whey proteins or soy protein isolate protect against 7,12-dimethylbenz(a)anthracene-induced mammary tumors in female rats.Int J Toxicol. 2001 May-Jun;20(3):165-74.Developmental effects and health aspects of soy protein isolate, casein, and whey in male and female rats.
    And there are many more.

    A crude analysis linking the protein source and IGF-1 production (although it’s interesting) fails to consider the other positive effects of these various proteins including IGF-1 binding factors and antioxidant production. That’s far too simple a model and it’s something that’s not yet properly understood.

    1. I should also add that glutathione is a major protector of the arterial endothelium, and heart disease still kills more of us than cancer.
      Just look up the relations between whey protein as a glutathione precursor and the prevention of heart disease via antioxidant protection of the endothelium (see Dr Mark Houston, for example).
      If you are an ethical Vegan there are good alternatives, but just because it’s animal sourced, it’s not scientifically invalid.

    2.  I see you enjoy studies on rats, as all of the studies you posted are based on rats. The first study looked at selenium in the whey protein when cows are fed with selenium supplements (selenium is abundant in the plant world). The only study that didn’t look at rats was the one on the single antioxidant glutathione. The researchers make the assumption that because whey protein contains high levels of this antioxidant whey protein will help prevent cancer. Does this mean that because chicken is an excellent source of selenium this food is now healthy to consume? No, food is a package deal. Taking isolated proteins in the form of whey and soy isolates promotes cancer growth by raising IGF-1 levels.

      1. They did not look at rats only, but other “animals” including humans and the rat studies were only part of their studies, which included epidemiological evidence and meta surveys. The equation includes IGF-1 inhibition also which you don’t mention and the bald statement that IGF-1 level raising = cancer, fails to take in other associated cancer inhibiting factors like selenium and glutathione as mentioned. 
        My point is that it’s not yet demonstrated that Veganism = low IGF-1 = low cancer. It may well be, but there is contradictory evidence that needs further study. Animal studies are a legitimate path on this process, but are never conclusive. I have no emotional need to ‘enjoy’ them. I do not have an ideology to prove. I just want to see good science in the service of better nutrition. I certainly lean towards the Vegan end of the spectrum in the Western context, but there is no need to force science into preconceived frameworks.

  9. Can someone please share what the letters mean after the numbers?  For instance, soya protein shows -0.04, animal protein is 0.18c, and animal plus soya protein is 0.27d.  ??

    In the end, I wonder if this means non-soy plant protein produces more IGF-1 than plain ol’ soya protein?  Thanks for the direction.  :)

      1. that is because soy protein isolate, contains more protein than cow milk. people don’t take soy protein isolate in place of dairy. soy milk has alot less soy protein in it. people take soy protein isolate in place of animal protein.

        this study shows animal protein and soy protein taken in the same amount. animal protein increases igf1 more.

  10. Dr. Gregor,  First of all I want to tell you how much I value the information you send each week. I find this series on IGF especially timely as I have a vegetarian friend that had cancer and has now switched to a vegan diet to bring his IGF levels down.  While I agree with the benefits of a vegan diet I am wondering about Omega 3s specifically DHA.  While flax, chia, walnuts etc are excellent sources of ALA it is impossible to eat enough of them to convert to DHA and EPA. Do you have any information about how fish and fish oil supplements impact IGF?

    1. Haely, what is your reasoning that Omega 3 levels cannotb e achieved through ALA alone?

      ALA is not converted effectively to DHA under the condition that one is consuming too many omega 6 fatty acids. Since most whole plant foods contain good ratios of omega 6 : omega 3, this is of no concern unless one is eating a lot of nuts other than walnuts, flax seed and chia seed. The National Academy of Sciences does not recognize EPA and DHA as essential. This means there is enough evidence for them to conclude that we can make enough of it without eating it in its preformed state. 

      In addition…
      Do vegetarians have to eat fish for optimal cardiovascular protection?1–3Am J Clin Nutr 2009;89(suppl):1S5S.

       Interest in the cardiovascular protective effects of n–3 (omega 3) fatty acids has continued to evolve during the past 35 y since the original research describing the low cardiovascular event rate in Greenland Inuit was published by Dyerberg et al. Numerous in vitro experiments have shown that n3 fatty acids may confer this benefit by several mechanisms: they are antiinflammatory, antithrombotic, and antiarrhythmic. The n–3 fatty acids that have received the most attention are those that are derived from a fish source; namely the longer-chain n–3 fatty acids eicosapentaenoic acid (EPA; 20:5n–3) and docosahexaenoic acid (DHA; 22:6n–3). More limited data are available on the cardiovascular effects of n–3 fatty acids derived from plants such as a-linolenic acid (ALA; 18:3n–3). Observational data suggest that diets rich in EPA, DHA, or ALA do reduce cardiovascular events, including myocardial infarction and sudden cardiac death; however, randomized controlled trial data are somewhat less clear. Several recent meta analyses have suggested that dietary supplementation with EPA and DHA does not provide additive cardiovascular protection beyond standard care, but the heterogeneity of included studies may reduce the validity of their conclusions. No data exist on the potential therapeutic benefit of EPA, DHA, or ALA supplementation on those individuals who already consume a vegetarian diet. Overall, there is insufficient evidence to recommend n–3 fatty acid supplementation for the purposes of cardiovascular protection; however, ongoing studies such as the Alpha Omega Trial may provide further information.

      1. Hi Toxins,

        Has there been any more recent research about this? I’m curious about StabbyRaccoon’s argument below in regards to Vitamin D.

        If Vitamin D controls cell-response to the mitogenic effects of IGF-1, (and vitamin D is found in animal products), isn’t it safe to say there’s no concern with IGF-1 level increases as long as one has optimal Vitamin D?

  11. There is somewhat of an association between IGF-1 levels and risk of some cancers, but I feel as if this narrative of yours is missing the bigger picture.  IGF-1 levels don’t determine the mitogenic effect of IGF-1 in the body, just like with any hormone, it’s the ability of the receptor to bind a hormone that determines its activity along with it. Vitamin d derivatives control the responsiveness of cells to the mitogenic effects of IGF-1 and when you control for vitamin d levels (not by any means the efficacy of vitamin d, but certainly an indication of the availability of vitamin d) the association mostly disappears I simply don’t think that there is any reason to worry about increases in IGF-1 levels if vitamin d is doing its job in the body. Of course there needs to be more research. This is what happens when some researchers become enamored with a hypothesis, they ignore evidence that might falsify it and then we reach poor conclusions.

    Since many people either have low levels of vitamin d or low levels of cofactors needed for its metabolism, and animal protein increases IGF-1 levels which may be problematic if vitamin d isn’t doing its job, we can expect any associations between animal protein and cancer to be attenuated after controlling for vitamin d. Although it’s not like that epidemiology is impressive if you control for cooking intensity (high heat is associated but not lower heat methods) or processed meat consumption.

    IGF-1 has numerous benefits, it is protective of the cardiovascular system keeps people vital throughout old age and may even oppose cellular aging This might mean that as long as people have good vitamin d bioactivity, they would benefit from this increase in IGF-1 from protein.

    1. You are misinformed, the most famous mainstream longevity specialists are now promoting water like fasting modalities; in order to foster decreases in IGF-1

      High levels of IGF-1 during adulthood cause cancer cells to grow, people with genetic disorders producing minute quantities of IGF-1 do not suffer from cancer, fact! Wherefrom all the interest in recent years emerged.

      Update your information.

      1. Apparently you didn’t read any of the information that I posted, my contention was that while IGF-1 is a factor in metastasis, its signaling depends on its receptor expression which determines its mitogenic effects and it can’t be said that if vitamin D levels and metabolism are sufficient to reduce receptor expression when appropriate an increase in IGF-1 levels would lead to a greater risk for developing a cancer. It could be that IGF-1 still matters while a person already has cancer regardless of vitamin d or any of its other cofactors, but the evidence for a causal relationship between serum IGF-1 and incidence of cancers in the presence of good control for IGF-1 receptors has been called into question and is supported by well-known mechanisms.

        If the increase in IGF-1 from consuming higher amounts of animal protein is claimed to be a significant factor in carcinogenesis, and vitamin D metabolism makes IGF-1’s role moot, then if animal protein does in fact contribute to cancer risk under normal circumstances it can’t be considered to contribute to cancer risk under conditions of ideal IGF-1 receptor control . I therefore suggest that you update your information on the epidemiology of animal protein and cancer risk. How so? To be determined, but skepticism on the issue is a must.

        1. I too would like to see some follow up on this. If Vitamin D (D3, found in animal products) mitigates the expression… then without isolating it, wouldn’t we see no difference in consuming animals and IGF-1 expression?

          Although, for those taking whey or soy protein powder, perhaps that is a moot point.

          1. That’s what these few bits of research suggest. IGF-1 levels might still rise but the receptors would be regulated and would reduce their expression in response to the right amount of IGF-1 signaling.

            With regards to whether or not there is generally no difference between IGF-1 signaling between differing amounts of animal protein, I think that it’s going to depend on the ability of vitamin d to regulate the receptors. Eating animal products doesn’t ensure adequate vitamin d, some contain some of it but deficiency is fairly common regardless.

            There is also the issue of magnesium and possibly other nutrients which help vitamin d metabolize to its active forms so just looking at prevalence of vitamin d deficiency might not be enough, you might also have to judge magnesium status.

            After that I suspect that the 10% increase in IGF-1 wouldn’t mean much, but yes we do need more research.

  12. Another video as always, Dr. Greger. Thank you (and your team!) for creating this wonderful and unimaginably helpful website.

    Although this doesn’t relate with this specific video per se, I wanted to ask if a specific website/organization has the most up-to-date and accurate recommended daily intake values? I’m asked quite (given I’m the resident doctor wannabe) how much of a given vitamin one should be eating, and I can only point the asker to the FDA values. Are these accurate values? Thank you in advance, Dr. Greger.

  13. With regards to ‘vitamin D’ supplements, vitamin D3 (cholecalciferol) is also used as a rodenticide. I find that troubling when you consider the vast majority of scientific studies examing health effects is undertaken on rodents due to their similarity to humans. So toxic to rodents, toxic to us ? I do not advise taking vitamin D3 supplements. I am curious of one brand from Garden of Life, RAW D3, which is apparently wholefood derived and not synthetic.

  14. I’ve looked pretty hard through these videos. Is there anything on how much protein we are able to absorb in one sitting. I heard on Christina Cooks that 20 grams is the max we can absorb. Is that true? Can you shed some light on that, Dr. Greger? Thanks,

  15. Is there any research you’ve come across about the defective BRCA gene, its relationship to IGF-1 growth, and how much a plant based diet reduces the risk for those who have this mutation?

  16. Dr. Greger – can you create a video about protein combining and veganism? I understand that it is a myth that vegans need to be careful in how they combine their foods to make sure they get adequate amounts of the amino acids needed. Is it? And if so, is there anything else recent research points to indicating there is something vegans need to worry about (besides B12 which is common in omnivores too)?

    1. There is no need to concern with oneself about getting enough protein.

      Firstly, I would like to quote the American Dietetics Association on their view of vegetarian diets and protein.

      “Plant protein can meet protein requirements when a variety of plant foods is consumed and energy needs are met. Research indicates that an assortment of plant foods eaten over the course of a day can provide all essential amino acids and ensure adequate nitrogen retention and use in healthy adults; thus, complementary proteins do not need to be consumed at the same meal ”

      Many say that plants foods are incomplete

      If “incomplete” means not containing all the essential amino acids then…. (the incomplete protein theory)

      1) All plant foods are complete as they contain all the essential amino acids.

      2) the only food that is not a complete protein is an animal food, gelatin.

      If “incomplete” means lacking in sufficient quantity of one or more amino acids…(the limiting amino acid theory)

      1) Getting all the amino acids in at once at the same meal, or even in the same day, as some may suggest, is not necessary due to the amino acid pool, which is a circulating level of amino acids in the blood, that the body can draw from if needed. As long as one follows a whole foods plant based diet, the amino acid pool will maintain a sufficient stock of any potentially needed (or limiting) amino acids.

      2) However, as long as one consumes enough calories, eats a variety of food, and limits junk foods and refined foods, and is not an all fruit diet, then they will get in enough protein and enough amino acids in sufficient quantity. There will be no limiting amino acids

      3) there is some evidence that the amino acids that are slightly lower (but adequate) in plant foods, may actually be a benefit to health and longevity and not a concern.

      Most every major health organization including the NAS, the WHO and the ADA all recognize these statements to be true.

      As long as you are eating when your hungry, till your full, there is no need to worry about getting enough protein.

      No other supplement people might need except vitamin D.

      1. Rami, you also need to supplement with B12 if you’re a vegan, and you need to make sure that you’re getting enough omega-3 fats — that they’re balanced with the omega-6. Dr. Greger talks about this in one of his yearly videos.

        1. Correct, I forgot to mention b12. A standard amongst plant based diets. I have posted here on this site many times regarding the importance of the omega 3:6 ratio, so yes I agree with you on that. My post above was in regards to supplementing though.

  17. Do we have any numbers on what the level of IGF-1 should actually be?

    According to this study; both low and high concentrations of IGF-1 promote cancer (along with low IGF-1 levels promoting higher CVD mortality).

    So I reckon that this is similar to blood glucose and insulin levels. There’s this one optimal concentration and it shouldn’t get too low or too high. Apparently the plant based diet puts it at the recommended level?

  18. While I can agree that Americans eat too much animal protein and even the wrong kind if it is not organic, when I look at some other cultures that do eat animal proteins such as the Japanese, or the Aleutian and Eskimo populations, they still have far better health measurement than even vegans and vegetarians in America. These people have the lowest Cancer rates in the world.

    1. The Japanese you are referring to are near vegan.

      Caloric Restriction, the Traditional

      Okinawan Diet, and Healthy Aging

      The Diet of the World’s Longest-Lived People and Its Potential Impact on Morbidity and Life Span

      Ann. N.Y. Acad. Sci. 1114: 434–455 (2007).

      TABLE 1. Traditional dietary intake of Okinawans and other Japanese circa 1950

      Total calories 1785

      Total weight (grams) 1262

      Caloric density (calories/gram) 1.4

      Total protein in grams (% total calories) 39 (9)

      Total carbohydrate in grams (% total calories) 382 (85)

      Total fat in grams (% total calories) 12 (6)

      Saturated fatty acid 3.7

      Monounsaturated fatty acid 3.6

      Polyunsaturated fatty acid 4.8

      Total fiber (grams) 23

      Food group Weight in grams (% total calories)


      Rice 154 (12)

      Wheat, barley, and other grains 38 (7)

      Nuts, seeds Less than 1 (less than 1)

      Sugars 3 (less than 1)

      Oils 3 (2)

      Legumes (e.g., soy and other beans) 71 (6)

      Fish 15 (1)

      Meat (including poultry) 3 (less than 1)

      Eggs 1 (less than 1)

      Dairy less than 1 (less than 1)


      Sweet potatoes 849 (69)

      Other potatoes 2 (less than1)

      Other vegetables 114 (3)

      Fruit less than 1 (less than 1)

      Seaweed 1 (less than 1)

      Pickled vegetables 0 (0)

      Foods: flavors & alcohol 7 (less than 1)

      Data derived from analysis of U.S. National Archives, archived food records, 1949 and based on survey of 2279 persons.

      Some points

      Their diet was 85% carb, and 6% fat. Sweet potatoes (a Japanese sweet potato) made up almost 70% of their calories. Nuts were less than 1% of calories (the equivalent of 1/10 of an ounce a day) Oil was less than 2% of calories (which is about 1 tsp a day) and sugars were less than 1% of calories (less than a tsp a day)

      The total animal products including fish was less than 4% of calories which is less then 70 calories a day. That is the equivalent of around 2 oz of animal products or less a day

  19. My kids are by wast majority vegan. I am 5.7 tall and my daughter is out of the chart when comes to her hight, over 100%. She is so tall she is taller than any child in her school who is 1 year older. Her estimated hight is definitely over 6ft. She is now 9. My son is 5 and he is pretty tall too. 65% for his hight. My husband is 6.5. My son looks like me and my daughter looks like him.

  20. I do see many short children and adults who are gorging on animal products. Some parents are forcing tons of cows milk in to their children to make them grow. In my opinion they are causing more harm to their kids. If their kids are short, they are just short. There are so many short people who ate whole live mega doses of animal protein and they are just short.

  21. I have acromegaly and my IGF1 levels are always high. Do you believe that, if I ate vegetarian or vegan that my IGF1 levels could come down to normal?… or is it different for someone with acro?

  22. Luigi Fontana’s study indicated that reduced intake of protein (0.8
    grams per day per kg of body weight – lowers IGF-1. However, I’m
    now seeing that animal protein appears to be the culprit rather than
    plant-based proteins (per your video on proteins). My question is, then, if I should track my
    animal protein intake and not be concerned about the plant-based component, and, if so, what would be the “reduced” RDA (per
    kg body weight) for animal protein intake?

      1. Thanks for your reply, Tommasina – and I have seen the videos, hence my question. I know animal protein is worse, but that’s a relative term. I’ve seen discussions where it’s been implied that plant proteins may actually LOWER IGF-1, although it seems it’s more the quality of a protein and its amino acid content that ultimately drives IGF-1. With many plant proteins being incomplete, they may have no effect on IGF-1…at least not increase it. My primary question is whether or not one should bother tracking ALL proteins one consumes or just animal proteins. Dr. Fontana was kind enough to answer my e-mail on the subject but was still ambiguous – he reiterated that RDA was 0.8g/kg body weight, also explaining that his studies were conducted using a “typical Western diet (i.e. lots of animal products, little beans or whole grains).” I could assume that would mean that the jury is still out on plant-based proteins, or it could mean that plant-based proteins don’t factor in, given he also sent me an article in which it was said that, “…. the high intake of animal (dairy) proteins in Western diets may play a role in PCa development and progression, whereas more traditional diets rich in proteins from cereals and legumes might partially inhibit PCa growth.” (PCa being prostate cancer). In the end, all I really wanted to know was whether I should track ALL proteins I consume (and keep to Fontana’s RDA) or only track the animal-based proteins and remain within the RDA for only those. Conversely, if I only track animal-based proteins, would the RDA be lower – say, 0.7g/kg of body weight? I’m basically looking for one number – a factor to use as an RDA for animal-based protein – as well as a confirmation that I can ignore (not track) plant-based proteins (possibly excluding soy, but I don’t intentionally eat soy anyway!). Hope that narrows down my question (if an excessively long explanation!).

  23. Hi Doc,

    Seems your old news just became “news” news.

    You are probably rolling your eyes.

    I’ve read and watched most of you thoughts/research and gone
    further looking for that magic bullet – exercise, to see if I’m building up my

    I’m 52, quite fit 5’ 8” 165 and do mid level cardio daily
    (heart rate 130-150)

    Also do moderate weight resistance.

    We eat “well,” but no doubt chicken and beef and deer and
    fish and eggs and cheese are part of it.

    I heard you “say” exercise and plant based is the trick, but
    most of what I’m reading says exercise can actually Increase IGF-1 and Decrease

    I have cancer in all four trees of family and while not
    completely a hypochondriacal – I’m getting close.

    What is exercise’s role, does intensity matter?

    Does the type of animal protein make a
    difference ie lean venison vs a marbled Delmonico?

    Thoughts would be so appreciated.

    Thank you.

    1. Hi Mark! Not that you’re looking to lose weight, but Dr. Greger has a great video on exercise vs. nutrition for weight loss: . For optimal health, it looks like cutting out animal products is the recipe. You might want to check out these three pages: ,, and . I hope that helps!

      1. Go vegan and lose weight great but you better get your cholesterol to make hormones, The CLA fat on animals is good for you. When your IGF-1 levels drop you go catabolic not anabolic. What do YOU want to accomplish? You can’t throw the baby out with the bathwater. If IGF-1 caused all of this cancer then ALL pro-bodybuilders would have cancer. I used to praise everything this Doc said. Not anymore. When you live it and experience it then you know what really works. REALITY

        1. There is no dietary need to consume cholesterol

          “Given the capability of all tissues to synthesize sufficient amounts of cholesterol for their metabolic and structural needs, there is no evidence for a biological requirement for dietary cholesterol.”

          Pro body builders are promoting cancer growth, and indeed promoting aging. Having elevated IGF-1 does not mean you automatically get cancer. Cancer must grow, and it is all about risk. Some may not even get cancer, but it is likely that those who have elevated IGF-1 can get cancer more easily.

          1. Sure, we have the fruitarians out there, The vegans, frugavores. We have bodybuilders that eat 36 eggs a day and they don’t drop dead of cancer. You probably won’t agree with this because your mind is already made up. If you want brain function and to build muscle and recover from an injury, especially when you get older you need to pay attention. and learn about the CAUSES of cancer. Children are more succeptable to getting cancer because their cells are dividing more rapidly(from radiation) And their IGF-1 levels are higher than your. That doesn’t mean that is the CAUSE of cancer IGF-1 is NOT a metabolic pathway to cancer. It is a metabolic pathway to growth. Don’t compare apples to oranges. Show me the body builders that promote cancer and aging. Sure you will get the EXTREMISTS that over do it. Look at the sports and athletes

            1. To think bodybuilders are healthy is astonishing, besides the elevated IGF-1 and endotoxemic effects of their diets and beyond all of the contaminants they consume, the supplementation of protein has shown to be more detrimental to health then recently thought.

              “In this regard it is of special concern that male adolescents in the fitness and bodybuilding environment consume high amounts (60–80 g/d) of leucine-rich whey- or casein-based protein concentrates to gain muscle mass, a procedure which is often associated with the development of acne…it is frightening to realize that more than 85% of adolescents of Western countries exhibit acne, whereas individuals of non-Western populations like the Kitava are not affected by this disease and other mTORC1-driven diseases of civilization.3,149 This implies that the majority of our Western population is living with over-activated mTORC1 signaling, a major pathogenic factor, which probably may pave the way for the development of other serious diseases of civilization”

            1. Dr. Mercola runs a for profit pseudo health business. I have no interest in reading his wild views, if you have primary sourced studies than share them, but Mercola is hardly the primary source, and is more gypsy than anything. His sale of tubs of coconut oil, advocating for raw milk, and insisting we avoid washing with soap so we can absorb vitamin d is evident of that. Like I said, no articles from your favorite health guru, primary sourced studies please.

              1. I find your response very entertaining, Please enlighten us all and share your rules on food, dietary intake, what is good and what is bad. Who will you see when you are sick? would you take colloidal silver or the anti-biotics or h202 to kill those pathogens that have invaded your body. If you are diagnosed with a cancer, What is your protocol? Chemo or apricot seeds?

  24. Please Dr. G, Set this high profile socialite straight about protein….”It’s hard being a vegan to eat enough good, quality protein and not have too much starch,” Dr. Hyman said over lunch at the Four Seasons restaurant in New York. “I know a lot of fat vegans.”

  25. I got a study for you… Take a look at ALL of the people around you today. Go to a vegan potluck and see if they can remember your name after 5 minutes. Go to a fastfood drive thru and take a look at those people. Go to the gym and look at those people. This doctor is too busy looking at garbage studies when reality is right in your face. Get out of the lab and look at the real world doc. I went Vegan for two years. It was a good cleanse but then all of a sudden you notice you can’t build muscle any more and the cognitive function is impaired. Anobolic gone catabolic. Then phospholipds and cholesterol aren’t there to make hormones etc. Just had 1/3 pound RAW liver with 3 RAW eggs. I’m recovering now. I’ll still have my salad later and a chlorophyll/spiralina/Maca cocktail too..

  26. IGF1 levels does not necessarily means that you’re gonna get cancer.IGF1 is a metabolic pathway for growth,yes growth in general from muscle tissue,bones,even organs BUT.There is a huge difference from ingecting into yourself,artificial IGF1 HGH etc and causing you body to secrete it naturall.When i say naturally i’m not talking about animal products (i am a vegan btw except some use of honey and bee pollen) animal product consumption is linked to a numerous deseases due to saturated fats,trans fats,high concentrations of sulfuring aminos even heme iron soy protein (which btw has some great health benefits,general the soy bean) is at least wrong.Ok consuming every day 1kg of soy probably is not good,as NOTHING is at very high quantities.Nothing wrong with natto,tempeh,tofu,soymilk,soybean,ans SPI.Asian people have been consuming soy for thousands of years without negative effects.Soy and especially SPI for people who are doing serious natural bodybuilding without use of AAS and artificial growth factors,and are also vegans believe me is a pain in the a$$ and soy protein is maybe the ONLY type of protein that has sufficient ratios of amino acids,from bcaas to even sulfur aminos (but in normal levels not the dangerous levels linked to the homocysteine rise in the blood).And for a vegan bodybuilder who must unfortunatelly play tetris with the food sources that he choses in order to give to his body the right ammounts of aminos,restricting SPI and soy foods so much does not make his goal any easier.There are sometimes that you need a meal thats complete with aminos and soy provides that meal with the additional benefits of lacking the saturated fats trans cholesterol and other endothelium inflammatory factors.I’m not saying that someone should go all the way to 200gr of SPI everyday or consuming a kilo of soy everyday but some servings of soy now and then even every day or the use of SPI which helps in positive nitrogen balance does not put you in the cancer risk team,thats just OVERexaggeration.Exercise,exposure to sunlight,vegan diet or for those who cannot something as close to vegan diet,fruits and vegetables which contains lots of antioxidants and phtochemicals,NO STRESS which is the global killer,healthy social relationships,keeping your cortisol and adrenaline levels down (except the necessary times),good sleep and melatonin function,clean air,no radiation,away from procceced foods and additives like msg etc and many more that i cannot even remember is the key to longevity.As long as your immune system is functioning well and your natural killer cells TP53 gene and many other cancer inhibitors are good and well,no cancer will ever show his face to you.With that logic we shouldn’t eat ANY ammount of protein and we should go straight to be breatharians living only with little water and sunlight exposure cause you like it or not the raise of IGF1 is inevitable i know that raise the IGF1 sky high MAYBE is not the best thing but we are not talking about external hormones and things like this.Stabby raccoon also has a point.And even if you still worry about the consumption of soy…

  27. I noticed on the slide towards the end that soya protein plus animal protein caused greater IGF levels than animal protein alone. This has implications for those who eat meat and then have a TVP patty 3 or 4 times per week to “be healthy”. I’m assuming that limiting your animal protein to cheese doesn’t get you out of this (darn it)?

    1. Good catch. I have not read the study, as I am not sure if that was animal and soy protein eaten together that boosted IFG-1 or if the foods were eaten throughout day. Cheese is full of fat and protein. A better source may comes from foods with fiber and antioxidants.

  28. What’s most important is what we truly thrive on.. What nature intended us to have. It’s proven in many countries with humans of freakishly impressive capabilities.. That have eaten this way for centuries..
    And also refer to the China study. A country without any disease likely found in the top 10 leading causes of death in the world for centuries.. Until it was westernised..
    Rice… Veg… Health… Longevity..

  29. Hello Dr. Greger,

    Recently I have noticed a lot of plant protein powders coming up from various companies. These include pea powder, rice powder, pumkin powder, and I’m sure many others. Is there any research being done to make sure these are safe? Extra plant protein doesn’t seem to be a problem, but I want to make sure. Thank you very much for all the time you put into these videos.

  30. I am having problems explaining animal/plant based protein to a friend of mine. He is saying that certain people can’t absorb plant protein as well as meat protein, and that most people absorb meat protein better. Years ago I probably would have agreed with him, but research and evidence over the years says different right?

  31. I’m no doctor, but I think the case with IGF-1 is not that it causes cancer. Cancer is merely cell reproduction gone awry, IGF-1 would not cause cancer but exacerbate and speed it up. I would think IGF-1 is essential for rebuilding damaged tissue and possibly should be recommended for people who are in need of healing processes.

    There was an argument in a different video that people with abnormal growth disorders did not have that much more relative muscle mass on average, but how many of those purposely induced muscular hypertrophy thru heavy training? Andre the Giant was well known to be very strong and muscular and purportedly did not even do much training either.

    Avoiding IGF-1 may be essential in those who have cancer and are trying to inhibit it’s reproduction while in the process of killing them off but may be a non-issue for otherwise healthy bodies, in fact it may be essential for us for recovery from injuries/training. Is it proven that IGF-1 causes our healthy cells to reproduce at a faster rate thus approaching the end of the telomeres sooner?

  32. Dear Dr. Greger

    I very much appreciate your informative videos and how you always show studies to support your views.

    I have been trying to become vegetarian almost 3 years now.However, I could not go without meat for more than 5 or at most 6 days. On the fifth day I get some strange symptoms like: muscle needles, fast heart beating, shortness of breath and strangely inability to THINK!

    I eat a lot of whole foods, I do try to combine beans and grains, and eat quite big volumes, but the symptoms remain, so eventually on the 7-th day I go back to eating meat again and the symptoms disappear.

    Now I truly can not figure it out. My GP prescribed Vitamin B, I also had a heart check and thank God it is also ok, I also made tests for electrolites, hemoglobine, which were on bottom border, but still in ranges. So currently I just couldn’t figure out what is wrong.

    I have been reading books constantly, nevertheless I can’t find the reason, so I decided to turn to you, perhaps you have had also other patients with similar symptoms. I truly do not wish to think that I can’t find a way around meat. I feel I need to do it since although I am 27, my cholestol is 7.9 mmol/ l and has been this high ever since I was 16 years old, so obviously I need to take some measures.

    Therefore, I would be very grateful if I receive some advice from your side.

    Thank you again for your efforts and I wish you all the best!

    Best regards,

    1. WantingToGetVegan: I commend you for your effort and am sorry you are experiencing such trouble. Good for you for not giving up!
      I don’t know what might be happening in your case. I have two theories for you that you can investigate. One is from famous and well respected Dr. Michael Klapper who has a talk about “failed vegans”. The bottom line of the talk is that you may not be able to go cold turkey because your body is addicted to meat. (He goes into the technical explanation to support this theory–one related somewhat to the idea in the next paragraph.) The solution: You may need to wean yourself off slooowly. If you are interested in the talk, you can see it on YouTube here:
      Another theory to investigate is a rare, but possible genetic defect where your body has a problem with “a mutation on chromosome 5 of a carnitine transport protein”. Because of that, you may need to either eat meat or (the safer option that doesn’t come with all the baggage that comes with meat) a pill. Dr. Greger has a video about a boy who went vegetarian and got sick. It turned out the boy had this particular problem. You could work with your doctor to see if you have this problem and if so, then you could investigate your options for dealing with it. Or maybe you have some other rare genetic problem that you could investigate and solve.
      I hope this post gives you some ideas that will lead to an answer for you. Let us know if you figure it out.

      1. Hello Thea,

        thank you very much for your post. I looked at Dr. Kapel’s video and it was really, really helpful to me! I think that the major vegan doctors should develop a research programme which involves blood tests, etc. which finds exactly what makes people fail on vegan diet – does their body not absorb well a particular nutrient or something else. I truly believe such a programme will be very useful having in mind how high the percentage of people giving up is.

        For me I decided to stop trying for the time being. Until such a programme is made to tell me exactly what is going on in my body and why these symptoms are happening, I think I will not attempt again to change my diet. I really don’t want to put my body in stress again without knowing exactly what is missing.

        Thank you very much, Thea! Your link to Dr. Kapel’s video really brought me relief that there may really be a physical reason I can not go even vegetarian.

        You brought back my inner peace on this topic!

        Thank you very much!

        All the best to you!

        1. WantingToGetVegan: It makes me happy that I brought you some peace.
          I waited to reply because I knew that I was going to get to hear all of Dr. Klaper’s talk live in a couple of weeks. The talk was on the various reasons that people fail on a vegan diet and how to prevent that failure. (FYI: You can purchase the talk if you want. It is titled “Thriving on a Plantbased Diet” on his website.) I have now heard the full talk and want to let you know what I learned. Dr. Klaper says that while some people may need 12-18 months to wake up the right genes, we can all do it. It’s not a matter of missing something or needing any tests. It is a matter of treating animal flesh as medicinal. Eat as little as you can and space it out as long as you can. At some point, even if it takes months of slowly expanding the amount of time between eating bits of flesh, you will be able to get off animal foods completely as your body will have healed itself from the damage of the food it has been given for the first years of your life.
          Me: There will never be the set of tests you are suggesting because there is no need. The answer is the same with or without any tests: slowly wean yourself off the animal flesh. And the sooner you do it, the faster you will maximize your health. As Dr. Klaper says again and again, “It’s the food. It’s the food. It’s the food.” Dr. Klaper is all about getting people on a whole plant food diet for maximum health. It’s is sad that you would use his talk as an excuse to not make change.
          That last bit is more harsh than I like. I *fully* understand being in an emotional place where you simply can’t face something. I would just suggest that you leave yourself an opening. Rather than saying you will never change until a highly unlikely condition comes to pass, instead you might tell yourself: “I am not in an emotional place to make this change right now. But I will be stronger in the future and will do it as soon as I can.” Just a suggestion. I did not want to leave things as they were since I felt that you picked up inaccurate information from that video clip. Best of luck to you on your journey.

  33. I’m an extremely healthy senior executive working
    full time. I’ve been a pescatarian for 35 years and have not eaten red
    meat, salt, sugar, most oils and fats or caffeine for 45 years. I gave
    up chicken 35 years ago. My weight and my waist are unchanged since
    the day I graduated from high school in 1954. I’m passionate about
    health and fitness. I currently have an IGF-1 issue that I need to discuss
    with a scientific medical expert. Can you direct me to an IGF-1 expert? Thanking you in advance for your prompt

  34. Maca root increasses tissue levels of IGF-1. Does it mean it is bad for our health? The Royal Maca company advertises that increase as beneficial.

  35. This is so stupid and misleading. IGF-1 is a normal hormone in your body, it stands for insulin growth factor 1. It helps your body to grow. Without it, your body can’t grow. Obviously too much growth leads to cancer.. but too little also makes you short and weak. So obviously eating meat is going to trigger your IGF-1 to rise (as with eating anything). The key is to balance your diet. This article is a vegetarian propaganda.. so misleading

    1. Muradona: Here’s the thing: This video is explaining how the human body gets too much IGF-1. This video is a small bit of info about how to get balance to your diet. The propaganda comes from the media telling you that somehow meat gives a diet balance–without any understanding of human anatomy and nutritional science. You’ve been hearing that propaganda your whole life. It is perfectly understandable that the truth would sound off to you. I invite you to explore the information on this site, especially the Summary videos which you can find on the home page. This is the first one and will help you to understand what the science has been telling us for decades.
      If this particular video seems narrow to you to, you might consider watching the other videos in the IGF-1 series to get the big picture. Also note that you can check the studies referenced in NutritionFacts videos by clicking the ‘sources cited’ button and looking at the new section under the video.

  36. Stumbled across this thread while watching other videos on this site. The question of “which animal
    protein” or “all animal proteins” causing a rise in IGF-1 is very important. I know this thread is 4 years old but I figured I’d post these references in case some other people eat whey protein along with plant based foods but not meat & dairy.

    One study, for example, specifically looked at whether it was casein or whey that caused increased IGF-1 levels and found that only casein was the culprit: whey left IGF-1 levels untouched. [2] Whey is also known for its immune-boosting powers, which should be an asset in fighting cancer as well.

    2) Eur J Clin Nutr, 2009 Sep, 63(9):1076-83, Epub 2009 May 27, “Differential effects of casein versus whey on fasting plasma levels of insulin, IGF-1 and IGF-1/IGFBP-3: results from a randomized 7-day supplementation study in prepubertal boys”

    It’s no secret that exercise, especially with intensity, increases Growth Hormone levels. IGF-1 is a metabolite, i.e. a byproduct, of Growth Hormone in the liver. So then the more you exercise, the more IGF-1 and the more cancer risk, right? Wrong! Researchers have found that exercise increases the sensitivity of IGF-1 receptor sites and so athletes consistently have lower IGF-1 levels. [3]

    3) “The Inter-Relationship Between Growth Hormone, IFG-1 and Cancer”, Rashid A Buttar, D.O., Visiting Scientist, North Caroline State University, As published in ‘Anti-Aging Medical Therapies, Volume 5’

  37. Just a question that I cant seem to find an answer to, and I apologize if it has already been covered somewhere.
    How does the spike of IGF-1 differentiate between sedentary individuals and athletes after consuming the same kind of protein? Could it be higher in athletes due to necessity of rebuilding muscle tissue?
    Thankyou (-:

  38. There’s evidence that for older adults, IGF-1 may be important in maintaining cognitive function:

    From the article: “Multiple studies have established that IGF-1 and its signaling pathway have an important role in cognitive decline in aged participants. Aleman and colleagues (98) reported an association between perceptual motor performance, information processing speed, and IGF-1 levels in participants 65–76 years of age. A similar association was noted between IGF-1 levels and measures of fluid intelligence (99). In addition, high IGF-1/IGF binding proteins-3 ratios were associated with better maintenance of cognition determined by scores on the 30-point Mini-Mental State Examination (100), and a similar correlation was noted among centenarians (101). In addition, in a 3-year longitudinal study, Dik and colleagues (102) noted an association between low levels of IGF-1 and reduced processing speed. Other studies find that IGF-1 messenger RNA levels are lower in the frontal cortex of middle age humans compared with young (103). Importantly, one of the conclusions of this paper was that it was not age per se that correlated highly with cognitive deficits but the diminished level of IGF-1 and decreased signaling through the insulin response substrate-PI3K and Akt pathways. These conclusions are supported by recent data indicating an important association between cognitive function and IGF-1 levels in healthy fit older adults (104).”

  39. I’ve heard that IGF 1 is as much an issue in isolated soy protein as it is in meat and in some instances isolated soy was worse. I’m curious if isolated pea protein like what will be in the “Beyond Meat” Burger is bad. Several of the ingredients are questionable for sure.

  40. Isolated pea protein may be healthier than isolated animal protein but it is still a long way from the UNPROCESSED WHOLE food that a whole food plant-based diet is based on. Many experts recommend using such products sparingly and more for transition while one learns to eat more healthy whole foods. Your concern is warranted and you don’t want to rely on processed protein products rather than the whole food versions such as tofu, seitan. Hope that puts things into perspective.

  41. I have read that soy protein as well as animal proteins raise igf-1 because of their high biological value. I also have heard it recommended for vegans to mix proteins. For example, a mixing 70% pea protein with 30% rice protein results in a high biological value protein mixture. If that is true, wouldn’t this mixture of proteins also raise igf-1 a lot? Wouldn’t consuming a meal with beans and rice in a certain ratio also raise igf-1? In which case, shouldn’t one abstain from eating legumes and grains in the same meal if trying to lower igf-1?

    1. DV,
      Good question! Its not necessary to “combine proteins” as long as you are eating a variety of plant foods such as the daily dozen. Since soy protein has a similar amino acid profile as animal proteins there is some concern, and studies suggest, that eating excessive amounts of soy (in the neighborhood of over 7 servings per day) will raise IGF levels. See the following link for a discussion of the studies on this matter. It appears that somewhere between 2 to 5 is the magic number of soy servings per day to get the benefits without raising IGF.

Leave a Reply

Your email address will not be published. Required fields are marked *

Pin It on Pinterest

Share This