Doctor's Note

For more on nutrient absorption, check out these videos:
New Mineral Absorption Enhancers Found
Omnivore vs. Vegan Nutrient Deficiencies
Juicing Removes More Than Just Fiber

And check out these videos on phytonutrient absorption in raw and cooked foods:
Raw Veggies Versus Cooked for Heart Disease
Kale and the Immune System
Second Strategy to Cooking Broccoli

And check out these videos on the benefits of the phytonutrient lycopene:
Treating Asthma With Fruits and Vegetables
Why Might Vegetarians Have Less HPV?
The Fruit Whose Juice Is Healthier

And check out my other videos on cooking methods

Also see my associated blog post: How to Enhance Mineral Absorption.

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  • Excellent suggestion, I will be cooking more of my veg after watching this.

    • Michael Greger M.D.

      Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. And check out the other videos on raw food. Also, there are 1,449 other subjects covered in the rest of my videos–please feel free to explore them as well!

      • Lauren Aldrich

        Hello, I started making green leaf/fruit/seed smoothies a regular part of my daily diet a couple weeks ago. I mostly feel great, but my digestive system has been screwed up in several ways, so now I’m wondering if because I am not masticating my foods but rather sucking them through a straw in liquid form, this has caused the nutrients to not break down by stomach enzymes, or maybe my brain doesn’t not realize that I am in fact ingesting foods because they are in liquid form. I believe that we are able to get more nutrients into our bodies when blended versus chewed, but are those nutrients actually being absorbed properly? My feces has been quite green and irregular, whereas before they were quite regular. Any thoughts on mastication being vital?

  • myjolina

    This is great to know – is their a list of foods that is available that shows which veggies are better cooked vs. raw?

  • sapire

    Hi Dr. Greger:

    Thank you for providing so much valuable information.

    In regards to raw food nutrient absorption – Have there been any studies performed on blended raw vegetables versus raw vegetables (in their natural form) nutrient absorption. I’m advised that blended vegetables are more easily absorbed than eating the whole raw vegetable in its natural form. I suppose a lot has to do with how much blending (chewing) you do before swallowing the mouthful?

    Regards – Colin Sapire

    • Michael Greger M.D.

      As you can see here, the heating itself seems to improve the bioavailability of lycopene. I would not be surprised if the blending helped too, though, so you could blend and heat and have the best of both worlds. :)

  • BPCveg

    Thanks for bringing this important study to our attention.

    Is it true that consuming raw foods leads to greater alertness than eating the corresponding quantity of cooked food?

  • Nice post, Doc.  Love, Light and Aliveness :-)

  • Tom

    You never take into account the amount of waste from cooked foods. Raw is clean (and logical), so who cares about what some lab people says. All medical science is based on that, we always have to measure things and now we are the sickest people in the history of mankind.

    • Toxins

      Tom, what waste do you speak of? When one is on a raw diet, this requires eating a lot of food all day just to satisfy energy needs and expenditures.There is no evidence whatsoever that a raw diet is “better” or “cleaner” or superior to a whole foods plant based diet. Nor should we idolize ancient people’s who may have eaten only raw as their lifespan consisted of an average of twenty to thirty years. This short lifespan is something I personally do not idolize.

      Current nutritional science is based on studies like these and is not based on how one feels about a diet. Furthermore, you are correct that many people are sick. That is why Dr. Greger is here to help others in showing them that they can prevent nearly all westernized chronic illnesses with a whole foods plant based diet.

  • Eric

    After listening to this most unscientific cooked-fooder apologistic nonsense, I’m more convinced than ever to stay 100% raw vegan. God, what junk “science”! What were the “raw” subjects conditions like BEFORE the tests? Many raw fooders had debilitating conditions before they went raw. I know young men and women who  win Olympic gold medals and ther championships being RAW VEGAN. Wake up!  Everyone converting to a raw diet from a cooked one improves their digestion, absorption, and energy, youthful appearance, healing ability, eliminate illness, shrink tumors in days, clear up skin problems. No cooked food diet will EVER compete with the benefits I have pesonally experienced and seen. Sure, there are some foods that need to be cooked before their poisons can be neutralized such as wild mushrooms and medicinal herbs, but that’s not the case with 95% of everything that;s edible.

    • Toxins

      There is actually no scientific evidence whatsoever that supports a completely raw diet over a cooked diet. A raw diet is more of a philosophy then any actual real scientifically supported diet. If your truly interested in seeing the opposing side of a raw food diet with open eyes then visit this link. They gather the evidence against a raw food diet quite well.

      Furthermore you have eliminated complex carbohydrates on a raw diet (such as beans, grains, potatoes and other starches). You cannot consume these foods without exposing your body to an abundance of antinutrients such as tannins, lectins, amylase inhibitors, phytic acid etc. What this means is that you will have to constantly be grazing all day to achieve adequate caloric needs.

      In addition, what is the point of a raw food diet when we have an abundance of scientific evidence showing that a vegan diet including mixed raw and cooked plants can eliminate chronic illnesses and extend ones  life span significantly. The most long lived populated, the Okinawans, once found in rural japan, had their diet composed of 70% complex carbohydrates, that is, sweet potatoes. They did not eat these sweet potatoes raw and they had the most centenarians per capita.

      Please provide some evidence showing that a raw food diet is superior to a cooked diet. I don’t mean a philosophical argument either, i mean actual peer reviewed scientific evidence.

      • I’m not 100% raw, but I would disagree with your assertion about beans, grains, potatoes and other starches. These items can be “cooked” in a dehydrator (up to @ 115) and still be considered raw. The reason for this is that the low temp does not destroy the vital enzymes. And remember, I am only seeking to learn new information and share what information I have, not looking for an argument.

        • Toxins

          The problem with dehydrating these foods is that the antinutrients such as amylase inhibitors, tanins, lectins and phytic acid are still present and these do not allow proper synthesis of calcium, protein, zinc and can create other problems as well.

        • DStack

          In addition to what Toxins said here, the whole idea of “vital enzymes” is (according to Dr. Greger, whom I trust) a myth. The enzymes are useful to plants, but mean nothing to our bodies.

    • Elizabeth Hawkes
  • How was chewing measured? If the test subjects did not chew thoroughly, therefore did not burst many plant cells for their nutrients, would that in part explain why subjects who ate cooked food with more plant cell ruptures had higher blood ß-carotene? Lycopene aside, I am not clear on what caused the difference between the groups.

  • Elizabeth Hawkes

    Dr Greger, I have been a whole foods vegan for 6 months but I am wondering if I should go raw. Please tell me if the claims below are accurate about cooking food. Thank you

    What is wrong with cooked foods?

    Applying heat to foods provides no nutritional benefit to the food and is detrimental to the person ingesting the cooked food. There are reported instances where, by heating food, certain nutrients are more easily released, like lycopene from tomatoes. However, this ignores that hundreds of other nutrients in that heated tomato were damaged or destroyed. And it also assumes that more of a specific nutrient is better, instead of trusting that the body knows how to extract just the right amount that it needs for optimal health. Many nutrients are deadly toxic if we overdose on them, and more is definitely not always better. Many foods that we cook would otherwise be unappetizing or inedible to humans, such as meats, grains, and starches, thus bypassing sensory safeguards that normally protect the body from ingesting unnatural and unhealthy substances. Studies have shown that the immune system often reacts to the introduction of cooked food into the bloodstream the same way it does to foreign pathogens such as bacteria, viruses, and fungi. Cooking food denatures the proteins, renders the fats carcinogenic, and caramelizes the carbohydrates. Many other nutrients are damaged, deranged, or destroyed by the heating process, leaving mostly empty calories. Regular consumption of cooked foods results in a detrimental enlargement of the pancreas.

    What are some of the toxins that accumulate in the body from eating cooked foods?

    Eating cooked meat creates excess uric acid and ammonia in the body, both of which are toxic to the system. The proteins in cooked food become denatured, and, as a result, the polypeptide bonds cannot be broken down into amino acids. These polypeptides are treated as foreign invaders and must be excreted through the kidneys. The cell wall of the kidneys doesn’t allow for easy transport of these substances, causing the distress that leads to kidney stones and eventually to kidney failure. Cooked grains cause fermentation in the body that produces gas, alcohol, and acetic acid; protoplasmic poisons that kill every cell with which they come into contact.

    • Toxins

      Do not trust raw food “doctrine”. It is mixed science with philosophical belief. Denaturing of proteins occur in stomach with the presence of HCL. Denaturing proteins allow stomach enzymes to easily break down the proteins into their simple amino acids. Cooking also deactivates anti-nutrients which include lectins, phytic acid, trypsin and α-amylase inhibitors. Cooking at extremely high temperatures, such as with cakes and cookies may pose minor health risk, but this is insignificant. Uric acid is a byproduct of all cells and is not specific to cooked foods. If these statements were true, studies should be present, yet these are unsupported statements and very much misconstrue the science. A trusted source is this write up from vegsource about raw food diet myths.

      • Elizabeth Hawkes

        Thank you so much for the link. I really enjoyed

      • Elizabeth Hawkes

        There’s just no scientific evidence not one for evolution from one species to the next. Lateral evolution, yes.

        • Dan

          Elizabeth, not that this is the place to discuss evolution, but there’s plenty of evidence which shows that we all evolved over time, from one species to another. There are thousands of books on the topic, hundreds of courses you can take, every museum can show you and every scientist can explain it further. There’s no debate about evolution AT ALL.

          • They won’t kick you out of the liberal atheists club for calling a theory a theory. Not a shred of evidence for the theory of evolution.

  • Too bad there are no studies on pulverization or juice. This is one of the only places where we are at odds, but thanks for the book tip “Becoming Raw” by Davis and Molina. I’m now into about a pound of dark leafy greens a day, and thanks to you I choose more nutritious foods across the board.

  • Hi Dr Greger, I’m confused about the safety of cooking foods in a microwave. I’ve read that it kills the nutrients in vegetables and other foods, and other articles I’ve read say it’s safe. Can you give me your opinion?

  • stupid. your body takes what it needs more is not better. and then this would also mean you are under carbed and have a lack of energy. we dont need more! more is not better!

  • Ann

    Dr greger could you do an article or video about skin turning yellow from healthy eating? i have been having this for years now. Sometimes more sometimes less (eyes are white btw)

  • According to a previous study on German long-term strict raw food dieters, “plasma carotenoids in raw food adherents are predicted mainly by fat intake.” (Long-term strict raw food diet is associated with favourable plasma beta-carotene and low plasma lycopene concentrations in Germans.) This is also emphasised by Dr. Greger, as consuming fat with vegetables increases absorption of nutrients. Some raw vegans strictly follow low fat diets, so it would be interesting to see the full diet of these participants and whether fat intake was a contributing factor to lower ß-carotene levels.

  • Crystena

    Like others, I too wonder if the study notes the fat intake at all of any of the subjects. How much does cooking affect nutrient absorption alone (without fat)? Dr. Greger, I’m actually concerned my carotene levels are too high; a recent blood test gave my carotene levels as 242 ug/dL. They say normal can be up to 300 but my skin is a little too yellow, at least to me. Since oils aren’t good for you, I was actually hoping cooked veggies without oil would not result in really high absorption. I mean if your eating a healthy diet anyways, you might not need super amounts of carotene for added protection and there’s other things in veggies that are good for you besides carotene which is why I’m still eating them, but at the same time hoping not eating any added fat will help with high carotene/yellow tone factor.

    What do you think?

  • Robin

    I want a cookbook and recipes… How about a section where you post NutritionFacts approved recipes. I am new to this and need some assistance. Thank you.

    • Thea

      Robin: Here are some resources you might find helpful.

      1) Consider going through the free 21 Day Kickstart program by PCRM. They will hold your hand for 21 days, including meal plans, recipes, videos, inspirational messages, and a forum where you can ask questions.
      (Click the green “Register Now” button.)

      2) Pick some good cookbooks and start making recipes. You don’t have to go cold-turkey and expect that you aren’t going to like every recipe you try. So, just keep trying dishes until you build up a set that you really like and are easy enough for you to make. Then you can just make those recipes and stop making your old ones. Some cookbooks that I recommend are:
      Let Them Eat Vegan
      Vegan On The Cheap
      Vegan Casseroles
      Everyday Happy Herbivore (or any book in that series)

      Or if you have a specific condition you want to work on, there are some great books that have recipes in the back for those conditions. Let me know if you want some suggestions for diabetes, heart disease, memory/dimentia or one that is good for athletes, etc. Actually, the main diet is the same for all of these conditions. But it is nice to get the specific books and recommended recipes when you are first starting out so that you start to get a handle on what you are looking for in terms of what is healthy.

      3) Check out some good recipe blogs. These sites have free recipes as well as some emotional support as you can read about the lives of others. Here are some sites people really like:
      There are A LOT more out there! So, keep looking until you find one or two that you like.

      4) Get a copy of Jeff Novick’s Fast Food DVD series. Jeff does a great job of giving simple, tasty, extremely healthy recipes, all in a mini cooking show format. Here’s one to get you started:
      The burgers and fries DVD is a good one too!

      5) Don’t forget your B12 supplement. Here are Dr. Greger’s overall nutrition recommendations. This will give you a very general, overall game plan along with some advice on specific nutrients to make sure you have all your bases covered:

  • James Bailey

    Aye, but how much beta-c do you need? How many other nutrients are broken down in the process?

  • Dawn

    Hello, I have been searching the Net to find a list or table of vegetables that are better raw or cooked. Do you have any info or links to this please? Thank you, Dawn

    • Joseph Gonzales R.D.

      Hi Dawn. I think both are good ways so I don’t have a particular list. Some foods however are better absorbed when cooked, like tomatoes, carrots and foods with beta-carotene. I would also cook the cruciferous veggies (cabbage, broccoli, cauliflower, Brussels sprouts).

  • Miriana

    On youtube there are so many frutarian that teach on payment how eat only tropical fruit raw is the best way to eat. I am concerned about this. They risck deficences. Maybe if you are jainist this is have a sense, but scientifically, what is the true? I have tried to eat only raw fruit without even greens but after 4 months I craving sodium, beens, greens and starch from rice and potatoes, and my hair loss very much, I felt without energy and I had hunger even if I eat 1 kg of bananas, I don’t feel sodisfation like with chickpeas and kale for example. So, have these person a scientific bases or are all lies? If you want I can give you several names. They support that only in raw food there is organic minerals and enzymes. Is it true?