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What Explains the Egg-Cancer Connection

The reason egg consumption is associated with elevated cancer risk may be the TMAO, considered the “smoking gun” of microbiome-disease interactions.

“We are walking communities comprised not only of a Homo sapiens host, but also of trillions of symbiotic commensal microorganisms within the gut and on every other surface of our bodies.” There are more bacterial cells in our gut than there are human cells in our entire body. In fact, only about 10 percent of the DNA in our body is human. The rest is in our microbiome, the microbes with whom we share with the “walking community” we call our body. What do they do?

Our gut bacteria microbiota “serve as a filter for our largest environmental exposure—what we eat”—and, “technically speaking, food is a foreign object that we take into our bodies” by the pound every day. The “microbial community within each of us significantly influences how we experience a meal…Hence, our metabolism and absorption of food occurs through” this filter of bacteria.

However, as you can see at 1:22 in my video How Our Gut Bacteria Can Use Eggs to Accelerate Cancer, if we eat a lot of meat, including poultry and fish, milk, cheese, and eggs, we can foster the growth of bacteria that convert the choline and carnitine in those foods into trimethylamine (TMA), which can be oxidized into TMAO and wreak havoc on our arteries, increasing our risk of heart attack, stroke, and death.

We’ve known about this “troublesome” transformation from choline into trimethylamine for more than 40 years, but that was way before we learned about the heart disease connection. Why were researchers concerned back then? Because these methylamines might form nitrosamines, which have “marked carcinogenic activity”—cancer-causing activity. So where is choline found in our diet? Mostly from meat, eggs, dairy, and refined grains. The link between meat and cancer probably wouldn’t surprise anyone. In fact, just due to the industrial pollutants, like PCBs, children probably shouldn’t eat more than about five servings a month of meats like beef, pork, or chicken combined. But, what about cancer and eggs?

Studies going back to the 1970s hinted at a correlation between eggs and colon cancer, as you can see at 2:45 in my video. That was based just on so-called ecological data, though, showing that countries eating more eggs tended to have higher cancer rates, but that could be due to a million factors. It needed to be put to the test.

This testing started in the 80s, and, by the 1990s, 15 studies had been published, of which 10 suggested “a direct association” between egg consumption and colorectal cancer, “whereas five found no association.” By 2014, dozens more studies had been published, confirming that eggs may indeed be playing a role in the development of colon cancer, though no relationship was discovered between egg consumption and the development of precancerous polyps, which “suggested that egg consumption might be involved in the promotional” stage of cancer growth—accelerating cancer growth—rather than initiating the cancer in the first place.

This brings us to 2015. Perhaps it’s the TMAO made from the choline in meat and eggs that’s promoting cancer growth. Indeed, in the Women’s Health Initiative study, women with the highest TMAO levels in their blood had approximately three times greater risk of rectal cancer, suggesting that TMAO levels “may serve as a potential predictor of increased colorectal cancer risk.”

As you can see at 4:17 in my video, though there may be more evidence for elevated breast cancer risk with egg consumption than prostate cancer risk, the only other study to date on TMAO and cancer looked at prostate cancer and did indeed find a higher risk.

“Diet has long been considered a primary factor in health; however, with the microbiome revolution of the past decade, we have begun to understand how diet can” affect the back and forth between us and the rest of us inside, and the whole TMAO story is “a smoking gun” in gut bacteria-disease interactions.

Since choline and carnitine are the primary sources of TMAO production, the logical intervention strategy might be to reduce meat, dairy, and egg consumption. And, if we eat plant-based for long enough, we can actually change our gut microbial communities such that we may not be able to make TMAO even if we try.

“The theory of ‘you are what you eat’ finally is supported by scientific evidence.” We may not have to eat healthy for long, though. Soon, Big Pharma hopes, “we may yet ‘drug the microbiome’…as a way of promoting cardiovascular health.”

What did the egg industry do in response to this information? Distort the scientific record. See my video Egg Industry Response to Choline and TMAO.


This is not the first time the egg industry has been caught in the act. See, for example:

For background on TMAO see my original coverage in Carnitine, Choline, Cancer, and Cholesterol: The TMAO Connection and then find out How to Reduce Your TMAO Levels. Also, see: Flashback Friday: How to Reduce Your TMAO Levels.

This is all part of the microbiome revolution in medicine, the underappreciated role our gut flora play in our health. For more, see: 

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Discuss

Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.


37 responses to “What Explains the Egg-Cancer Connection

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  1. I was texting all night with my egg-eater friend who went to the ER about 1:30 in the morning.

    They haven’t figured out what is wrong with her yet, but I helped her get a list of things they could test for.

    On the list of possibilities based on WebMD is tumor and I thought about this.

    She has excruciating nocturnal pain, plus nausea and so many other symptoms. They crossed 5 things off of my list and they gave up and she went home about 6:30 this morning with an appointment with her PC.

    They gave up, but my list is much longer than theirs.

    I am hoping that her PC will have his own list.

    1. I like the article about eggs. I can’t eat them anyway because of allergy and bad reactions, not pleasant!
      Eliminating them from my diet was not hard!

  2. They didn’t look for tumors or disc problems or other things on the Nocturnal excruciating pain list.

    She just got onto Medicare a few days ago, and she has been going through this for months but it is getting so bad that she is crying, so I told her, she should have them test for everything, if they will.

    They wouldn’t.

      1. I agree, and the sprays enable me to limit my oil consumption since far less of a spray is needed than using regular liquid oil. However, the spray contains lecithin, which I believe contains choline, so was wondering if this means it forms TMAO. Still wondering.

        1. Bob:
          Choline is an essential nutrient, which one must obtain from the diet. (Human body can make very small amount of choline, not sufficient to supply the daily need.) But, if you’re a vegan, you don’t have to worry about choline in food because your gut doesn’t harbor bacteria that can convert choline into trimethylamine.

  3. On the road to a healthy diet, I’ve found eggs (and cheeses) particularly difficult to give up, although over this last decade I’ve certainly reduced them both now by more than 90%. So handy for quick & tasty lunches!

    I guess that because eggs are so unhealthy, that our ancient ancestors didn’t eat them often or else we would have evolved differently. Strange, as you’d think that eggs would have been a readily available source of protein & energy.

    1. There are many, many vegan cheeses available just about everywhere now. Unfortunately, probably not all that healthy since they are high fat. Tasty and quick. Yes fat and refined sugar are addictive chemicals.

    2. NutritionChat.net,

      Have you tried JUST Egg in either the liquid or patty form?

      During my COVID processed food spree, I tried the patty form and made faux egg on a thin bagel.

      The texture and flavor is close enough to egg that it just needs you to spice it the way you spice your eggs. It is probably bland if you don’t use anything at all, but there is no aftertaste and that is really amazing.

      They are getting so good at these processes.

      As far as cheese goes, I am still trying to figure it out. I like Follow Your Heart faux slices – though I watched a taste test where a man was blindfolded and he said that the Mozzarella and Cheddar styles were exactly the same and I believe him.

      I don’t use them often, but I did do a lot of Amy’s vegan pizza for a few months and they have gotten so good at faux cheeze that there isn’t any need to hang onto real cheese

      I try not to use it.

      The version of cheeze that I am trying to figure out is the one used by Ark in their cauliflower and cheeze dish at Whole Foods.

      I find cashew sauce to be a good texture, but not the right approximation of cheeze and I probably eat too many cashews when I make it because I am generous with sauces.

      Working on it because I don’t want the fat of the processed ones.

  4. “TMAO made from the choline in meat and eggs” – The should say “egg yolks” as the whites do not have choline. The other possible pathway from egg yolks is the arachadonic acid which has a known pathway to inflammation.

    1. A small amount of choline in egg whites, according to this source: “Whole eggs provide ample amounts of protein, with each large egg providing 35 percent of the daily choline requirements for women or 27 percent for men. An egg white contains just 2.7 milligrams of choline — less than one percent of the recommended daily intake.” FOUND AT: https://healthyeating.sfgate.com/disadvantages-egg-whites-8738.html#:~:text=Whole%20eggs%20provide%20ample%20amounts%20of%20protein%2C%20with,than%20one%20percent%20of%20the%20recommended%20daily%20intake.

  5. I am quite worried about being choline deficient. You are supposed to get about 450 mg a day as a woman and on a plant based diet , when I do the sums , I get nowhere near that. I am 62 and I eat breakfast and lunch , no dinner, which just keeps my weight stable despite quite a bit of exercise . I also struggle to get enough protein and now I am concerned about choline , as on ultrasound my liver shows the beginnings of NAFLD. This is also linked to oversupplementation of B12 I think, as I follow the vegan guidelines. I am finding it hard to keep things in balance and would appreciate your comments.

    1. Susan, you are right to be concerned, especially if starting NAFLD.
      Some other nutrients can lower your requirement for choline, such as folate and betaine. So adding lots of greens, and wheat bran, for instance can help. Note the amount of the servings is 100 grams which is quite a bit of spinach for instance. Some people cannot tolerate this amount of spinach, but that much kale is great.
      (Btw, I do recommend using a food scale till you get an idea of vegetable portion size.)
      If you are WFPB and not vegan, fish like sardines and canned salmon help also. These also supply protein, as do many soy products.
      An article on choline-
      https://lpi.oregonstate.edu/mic/other-nutrients/choline

      And one on betaine-
      https://academic.oup.com/ajcn/article/80/3/539/4690529

      1. Thanks for replying to me. I eat a lot of wheat bran and quite a lot of greens, although there is a limit as you say to how many greens I want to eat. I don’t think Dr Gregor would recommend fish as part of a Wholefood plant based diet but I do add some in to up the protein. Without eggs it still leaves a great choline deficiency though …

    2. Well, try some PAM spray, it seems to have choline in around 450 mg, just get the original with lecithin, not the new one with mostly canola. HTH

    3. Interesting. My understanding is that NAFLD is linked to B12 deficiency rather than overconsumption of B12.
      https://pubmed.ncbi.nlm.nih.gov/21804402/

      Humans naturally produce some choline and the US National Institutes of Health comment

      ‘Although most people in the United States consume less than the AI of choline, frank choline deficiency in healthy, nonpregnant individuals is very rare, possibly because of the contribution of choline that the body synthesizes endogenously [1,5].’

      They also note

      ‘ Cruciferous vegetables and certain beans are also rich in choline, and other dietary sources of choline include nuts, seeds, and whole grains.’
      https://ods.od.nih.gov/factsheets/Choline-HealthProfessional/

      Soybeans appear to be a particularly good source of choline. They are also a good source of protein. They are quite high in fat though.

      I’m personally dubious about the current desire for high protein consumption bearing in mind that long lived peoples on traditional WFPB diets like the Okinawans and other Japanese did remarkably well on diets averaging 9% and 13% protein respectively.

      https://www.researchgate.net/publication/5859391_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

      1. Thanks for your reply. If NAFLD is linked to low B12 I do not think the B12 can be causing it in my case, as because of supplementation my B12 active levers are way over the normal range . So that leaves the choline problem. It’s quite hard to figure out what to do , whether to eat more eggs , liver , etc with all the problems Dr Greger points out , or stick to the WFPB diet. I had my genes analysed and they said genetically I am carbohydrate intolerant , should eat more fats. Again something to struggle with as a vegan eating lots of grains etc. I wish there were doctors who knew something about this to consult.

        1. Interesting. I’ve never heard of genetic testing indicating that a person is carbohydrate intolerant. Was this the result of testing by a reputable organisation, not a recommendation from some ‘alternative’ service provider?

          The reason I ask is that carbohydrate intolerance is usually diagnosed by a simple breath test.rather than some fancy genetic test
          https://www.merckmanuals.com/professional/gastrointestinal-disorders/malabsorption-syndromes/carbohydrate-intolerance

          If you really are carbohydrate intolerant and this is confirmed by a licensed medical practitioner, you could consider a plant based low carb diet like this one
          https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/415074

          or just Google ‘eco Atkins’

          1. Thanks for your very interesting reply. The paper outlines just the sort of diet I think might be helpful to me. I have already replaced all refined starch with home made items made from Lonjevity foods , you might like to look at their website, Lonjevity-foods.com. They focus on very high fibre , high protein , high fat flours, and this seems very useful to me. They also favour a lot of animal products Alongside this , but I don’t agree with that…
            The genetic analysis was done by self decode, linked to self hacked, it seemed quite detailed and confirmed many things I already knew or suspected about my physiology. I am still puzzling over the choline issue , however , but I guess it is possible just to supplement , I wonder if plant choline has the same TMAO issues as eggs..

            1. To be frank, I wouldn’t place any reliance at all on advice from self hacked or self decode. There’s no real science behind what they say. Great marketing but poor science.

              You might want to consider talking to your licensed medical practitioner before taking any action in this area. Low carb diets should be avoided if at all possible because they are associated with a significantly increased risk of early death

              ‘Overall, the analysis using data from the survey found that those who consumed the least amount of carbs were 32 percent more likely to die prematurely from any cause. This was in comparison with participants who ate the most carbs.

              Also, low carb consumers were 51 percent more likely to die from coronary heart disease, 50 percent more likely to die from cerebrovascular disease, and 35 percent more likely to die of cancer. The associations were strongest among older, non-obese people.

              These results were replicated in the meta-analysis, which found that the overall risk of death from any cause was 15 percent higher in people who consumed the least amount of carbs, the risk of cardiovascular death was 13 percent higher, and that of dying of cancer was 8 percent higher.’
              https://www.medicalnewstoday.com/articles/322881#Why-low-carb-diets-should-be-avoided

              1. Well self decode understood some very specific things very accurately. So I’m not so sceptical of them.
                My medical practitioner is very overweight and just tells me to have a bagel.
                I think the low carb diets that cause cancer are animal based ones? I would like to loose a little weight which seems impossible without low carb as I only have one and a half meals a day.
                Too little protein causes gastric upset and wasting muscles. Too little choline does cause NALFD and I don’t know what else this might be caused by. I am not sure the Okinawams had Western physiology.

                1. OK but as I understand it, it is almost impossible to be protein deficient on any diet that provides sufficient calories. Official US Government figures assess that adult females should aim to consume just 46 grammes per day of protein. Dr Greger also has a number of informative videos on protein issues

                  https://health.gov/our-work/food-nutrition/2015-2020-dietary-guidelines/guidelines/appendix-7/
                  https://nutritionfacts.org/?s=protein

                  Yes, I imagine that most of those people on low carb diets were basing them on animal foods rather than plant foods. That could be a possible explanation for the increased mortality associated with low carb diets Low carb plant based diets probably aren’t as dangerous. However I don’t think that there is any good evidence that they are beneficial. For example, this study found (LCD – low carb diet)

                  ‘Adherence to an LCD high in animal sources of protein and fat was associated with higher all‐cause and cardiovascular mortality (hazard ratios of 1.33 [95% CI: 1.06 to 1.65] for all‐cause mortality and 1.51 [95% CI: 1.09 to 2.07] for cardiovascular mortality comparing extreme quintiles). An increase in adherence to an animal‐based LCD prospectively assessed from the pre‐ to post‐MI period was associated with higher all‐cause mortality and cardiovascular mortality (hazard ratios of 1.30 [95% CI: 1.03 to 1.65] for all‐cause mortality and 1.53 [95% CI: 1.10 to 2.13] for cardiovascular mortality comparing extreme quintiles). An increase in adherence to a plant‐based LCD was not associated with lower all‐cause or cardiovascular mortality.’
                  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4323805/

                  As you can probably guess, I am sceptical about low carb diets and low carb web sites in general. They seem risky. I think that they are popular because of slick marketing rather than good science. However, while they are not my cup of tea, I wish you luck with self-hacked and self-decode. My impression is that they are a bit like horoscopes ….. there’s always something in them that everybody can relate to.

                  Oh, regarding weight loss, have you viewed Dr Greger’s presentation on this topic?
                  https://nutritionfacts.org/video/evidence-based-weight-loss-live-presentation/

  6. Interesting article however many societies with the longest lived peoples consume a higher than average proportion of eggs.
    The studies should differentiate between eggs consumed and the total volume of meat consumed AND what type of meat that is.
    Based on simple consumer habits in western society when are eggs consumed without bacon or some other form of meat ?
    The presumption that eggs are the base cause flies in the face of long term studies (well over 70 years) that most of the top 10 longest surviving groups of people have a very low red meat consumption (as they simply can not afford this luxury) but a much higher than average egg consumption.
    I am a private citizen and have no vested interest in promoting higher egg consumption whatsoever.

    1. Can you provide any data/evidence that longest surviving people have higher than average egg consumption?

      That claim sounds like Egg Nutrition Center research … look at rich people in wealthy economies with advanced medical health care systems and compare them to poor people in poor countries with poor medical and public health systems.systems. The rich people have greater longevity and eat more eggs. The poor people have higher mortality and eat fewer eggs.

      Okinawans, Japanese etc on traditional WFPB diets were very long lived and had very low egg consumption.
      https://www.researchgate.net/publication/5859391_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

  7. Dr. Greger’s video [https://nutritionfacts.org/video/how-to-reduce-your-tmao-levels/] mentions how Brussels Sprouts will inhibit FMO3 and reduce blood TMAO levels.
    source: Biochemical Pharmacology, Volume 58, Issue 6 (1999), 1047-1055

    Here are a few other foods that will also reduce blood TMAO levels.
    Garlic and Allicin: Journal of Functional Foods 15 (2015), 408–417
    Grape Pomace / Resveratrol: Nutrients 2019, 11, 139

    It would be easier to convince people to eat a food, or take a supplement that prevents the conversion of choline and/or carnitine into TMAO, rather than to completely restrict consumption of eggs and meat altogether.

  8. “You are what you eat” is actually a famous quotation from the German philosopher Feuerbach. He was a scientific materialist – so he meant what you eat is all there is to you. No soul/spirit etc. So, I hear that phrase often in class and usually explain it might meat something other than a joke “I must be all Twinkies and bologna!” It actually has a philosophical component. Dr. M.

  9. I doubt this comment will be publicized since it goes against Dr. Greger’s biases. In fact it might even be caught in a spam filter and not approved. It would be nice if he changed his mind once new data is published. And correct himself. But it’s interesting that TMAO-cancer is now the theme, after TMAO-heart disease has been proven wrong via Mendelian randomization “Natural RCT”, as Dr. Greger puts it. And I haven’t eaten eggs or any animal products over 4-5 years in case you’re wondering about my biases.

    “Assessment of Causal Direction Between Gut Microbiota-Dependent Metabolites and Cardiometabolic Health: A Bidirectional Mendelian Randomization Analysis”, 2019, Jia et al. Diabetes.

    Also see “Acetyl-L-Carnitine Supplementation and the Treatment of Depressive Symptoms: A Systematic Review and Meta-Analysis”, 2018, Veronese et al.

    Choline is necessary for liver function and cognition. Acetyl-L-Carnitine supplementation reduces depressive symptoms.

    Though choline deficency ruins the liver, but at the same time keeps a lot of triglycerides from entering the blood which are causally associated with depressive symptoms etc.

    See “Causal relationships between blood lipids and depression phenotypes: a Mendelian randomisation analysis” (2020) So et al.

  10. I am 70 years old, and I have prostrate cancer. The biopsy was done about 7 months ago. I had already finalized my switch to the Dr. Greger diet, about a month before, after easing into it the previous 6 months, but of course years of too many eggs and too much cheese and butter took their toll. The only thing I still allow myself is a 2 eggs scrambled with broccoli and green onions on Sunday mornings. I do that because I thought I had read about 2 months ago that this would be ok, as my body has adjusted such that that much is safe.

    I am writing today to clarify once and for all that 2 eggs a week is ok now that I am eating healthy in every other respect. An answer to my query would be much appreciated.

  11. Boboroma,

    It’s impossible to say definitively however, in hearing your situation I would suggest that you discontinue the eggs to be on the safe side, reducing the cancer potential.

    As an alternative, perhaps experiment and test for TMAO and/or other indices such as, total and free PSA, CRP or others both without an egg meal that day and then one with your eggs ?

    Dr. Alan Kadish moderator for Dr. Greger http://www.Centerofhealth.com

  12. I’m not so sure about that 10:1 statistic of bacteria to human cells. I looked it up and that appears to be a rather old (like 1970) textbook statistic that is pretty much de-bunked but also very difficult to measure. Here is the article I found that summed it up well: https://www.google.com/amp/s/www.sciencealert.com/how-many-bacteria-cells-outnumber-human-cells-microbiome-science/amp
    They claim they current believed average ratio to be 1.3:1.

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