Medical Meat Bias

When famed surgeon Michael DeBakey was asked why his studies published back in the 1930s linking smoking and lung cancer were ignored, he had to remind people about what it was like back then. We were a smoking society. Smoking was in the movies, on airplanes. Medical meetings were held in “a heavy haze of smoke.” Smoking was, in a word, normal. Even the congressional debates over cigarettes and lung cancer took place in literal smoke-filled rooms. (This makes me wonder what’s being served at the breakfast buffets of the Dietary Guidelines Committee meetings these days.)

I’ve previously talked about a famous statistician by the name of Ronald Fisher, who railed against what he called “propaganda…to convince the public that cigarette smoking is dangerous.” “Although Fisher made invaluable contributions to the field of statistics, his analysis of the causal association between lung cancer and smoking was flawed by an unwillingness to examine the entire body of data available…” His smokescreen may have been because he was a paid consultant to the tobacco industry, but also because he was himself a smoker. “Part of his resistance to seeing the association may have been rooted in his own fondness for smoking,” which makes me wonder about some of the foods nutrition researchers may be fond of to this day.

As I discuss in my video Don’t Wait Until Your Doctor Kicks the Habit, it always strikes me as ironic when vegetarian researchers are forthright and list their diet as a potential conflict of interest, whereas not once in the 70,000 articles on meat in the medical literature have I ever seen a researcher disclose her or his nonvegetarian habits––because it’s normal. Just like smoking was normal.

How could something that’s so normal be bad for you? And, it’s not as if we fall over dead after smoking one cigarette. Cancer takes decades to develop. “Since at that time most physicians smoked and could not observe any immediate deleterious effects, they were skeptical of the hypothesis and reluctant to accept even the possibility of such a relation”—despite the mountain of evidence.

It may have taken 25 years for the Surgeon General’s report to come out and longer still for mainstream medicine to get on board, but now, at least, there are no longer ads encouraging people to “Inhale to your heart’s content!” Instead, today, there are ads from the Centers for Disease Control and Prevention fighting back.

For food ads, we don’t have to go all the way back to old ads touting “Meat…for Health Defense” or “Nourishing Bacon,” or featuring doctors prescribing meat or soda, or moms relieved that “Trix are habit-forming, thank heavens!” You know things are bad when the sanest dietary advice comes from cigarette ads, as in Lucky Strike’s advertisements proclaiming “More Vegetables––Less Meat” and “Substitute Oatmeal for White Flour.” (You can see these vintage ads from 2:34 in my video).

In modern times, you can see hot dogs and sirloin tips certified by the American Heart Association, right on their packaging. And, of all foods, which was the first to get the Academy of Nutrition and Dietetics’ “Kids Eat Right” logo on its label? Was it an apple? Broccoli, perhaps? Nope, it was a Kraft prepared cheese product.

Now, just as there were those in the 1930s, 40s, and 50s at the vanguard trying to save lives, today, there are those transforming ads about what you can do with pork butt into ads about what the pork can do to your butt: “Hot Dogs Cause Butt Cancer—Processed meats increase colorectal cancer risk” reads an for the Physicians Committee for Responsible Medicine’s “Meat Is the New Tobacco” campaign, which you can see at 3:56 in my video. As Dr. Barnard, PCRM president, tried to convey in an editorial published in the American Medical Association’s Journal of Ethics, “Plant-based diets are the nutritional equivalent of quitting smoking.”

How many more people have to die before the Centers for Disease Control encourages people not to wait for open-heart surgery to start eating healthfully?

Just as we don’t have to wait until our doctor stops smoking to give up cigarettes ourselves, we don’t have to wait until our doctor takes a nutrition class or cleans up his or her diet before choosing to eat healthier. No longer do doctors hold a professional monopoly on health information. There’s been a democratization of knowledge. So, until the system changes, we have to take personal responsibility for our health and for our family’s health. We can’t wait until society catches up with the science again, because it’s a matter of life and death.

Dr. Kim Allan Williams, Sr., became president of the American College of Cardiology a few years back. He was asked why he follows his own advice to eat a plant-based diet. “I don’t mind dying,” Dr. Williams replied. “I just don’t want it to be my fault.”


I find this to be such a powerful concept that I have come at it from different angles. For other takes, check out Taking Personal Responsibility for Your Health and How Smoking in 1959 Is Like Eating in 2019. Are the health effects of smoking really comparable to diet, though? Check out Animal Protein Compared to Cigarette Smoking.

The food industry certainly uses the same kind of misinformation tactics to try to confuse consumers. See, for example:

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:

What Meat and Eggs Do to Our Microbiome

As I’ve explored before, whether young or old, male or female, smoker or non-smoker, with high blood pressure or low blood pressure, high cholesterol or low, having high levels of a toxic compound called TMAO—trimethylamine oxide—in the bloodstream is associated with a significantly higher risk of having a heart attack, stroke, or dying over a three-year period. Where does TMAO come from? As I investigate in my video How to Develop a Healthy Gut Ecosystem, the choline in foods like eggs can be turned by gut bacteria into TMAO, which is then absorbed back into our system. And, the more eggs we eat, the higher the levels climb, as you can see at 0:41 in my video.

Given the similarity in structure between carnitine and choline, Cleveland Clinic researchers wondered if carnitine found in red meat, energy drinks, and supplements might also lead to TMAO production and put it to the test. As you can see at 1:00 in my video, if you feed omnivores, those who regularly eat meat, a steak, their TMAO levels shoot up. Those who eat strictly plant-based may start out with almost no TMAO in their system, presumably because they’re not eating any meat, eggs, or dairy. But, even if vegans eat a sirloin, still almost no TMAO is made. Why? Presumably, they don’t have steak-eating bacteria in their guts. Indeed, it was found that no TMAO is produced if you don’t have TMAO-producing bacteria in your gut. If you don’t regularly eat meat, then you’re not fostering the growth of the meat-eating microbes that produce TMAO.

This suggests that once we develop a plant-based gut ecosystem, our bacteria will not produce TMAO, even if we eat meat every once and awhile. However, we still don’t know how rapidly gut bacteria shift after a shift in our diet—but it does not appear to be all or nothing. If men eating the standard American diet are given two sausage, egg, and cheese biscuits before and after just five days of eating lots of similarly high-fat meals, their TMAO production boosts even higher, as you can see at 2:09 in my video. So, it’s not just whether we have the bad bugs or not. Apparently, we can breed more of them the more we feed them.

Meat-free diets, on the other hand, can also have been “demonstrated to have a profound influence on human metabolism.”Just by analyzing a urine sample, we can tell what kind of diet people eat, based on measurements like how low TMAO levels are in the urine of those eating egg-free vegetarian diets, as you can see at 2:26 in my video. At 2:43 in my video, you’ll see that we can even take the same people rotate them through three different diets, and determine who is on a high-meat diet, low-meat diet, or no-meat diet, based in part on the different compounds churned out by the different gut flora or different flora activity after just about two weeks on the different diets. It’s possible that some of the beneficial effects of whole plant foods may be mediated by the effects they have on our gut bacteria. At the same time, the standard American diet may increase the relative abundance of undesirables that produce toxic compounds including TMAO (as you can see at 3:07 in my video).

Strictly plant-based diets have gained acceptance as a dietary strategy for preventing and managing disease. Perhaps, in part, this is because of their rather unique gut flora, with less of the disease-causing bacteria and more of the protective species. So, all along, we thought the reason those eating plant-based had lower heart disease rates was because they were eating less saturated fat and cholesterol, but maybe their lower TMAO levels may also be contributing to their benefits, thanks to their reduced ingestion of carnitine and choline.

I talked about the egg industry response to the choline revelation in Egg Industry Response to Choline and TMAO. How has the carnitine supplement industry reacted? In response to the research implicating carnitine in TMAO production, the former vice president of AdvoCare—a multilevel marketing company that sells carnitine supplements like AdvoCare Slam while getting slammed with lawsuits finding them guilty of being “engaged in false, misleading or deceptive acts or practices” and forced to pay more than a million dollars—questioned whether there was a secret vegan conspiracy at the Cleveland Clinic. Restricting our intake of meat or carnitine supplements to prevent our gut bacteria from making TMAO, he argued, is like trying to prevent car accidents by restricting the sale of fuel.

Okay…but there are benefits to transportation. We’re talking about TMAO, which may be fueling our epidemic of heart disease, the number-one killer of men and women in this country. As far as I’m concerned, the more we can cut the fuel for that, the better.


For more background on TMAO, see Carnitine, Choline, Cancer, and Cholesterol: The TMAO Connection, then find out How to Reduce Your TMAO Levels.

Our gut flora are what we eat. Check out:

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:

The Role of Meat and Dairy in Triggering Type 1 Diabetes

Type 1 diabetes “arises following the autoimmune destruction of the insulin-producing pancreatic β [beta] cells…[and] is most often diagnosed in children and adolescents, usually presenting with a classic trio of symptoms” as their blood sugars spike: excessive thirst, hunger, and urination. They need to go on insulin for the rest of their lives, since their own immune systems attacked and destroyed their ability to produce it. What would cause our body to do such a thing? I examine this in my video, Does Paratuberculosis in Milk Trigger Type 1 Diabetes?

Whatever it is, it has been on the rise around the world, starting after World War 2. “Understanding why and how this produced the current pandemic of childhood diabetes would be an important step toward reversing it.” A plausible guess is “molecular mimicry, whereby a foreign antigen (bacterial or viral) provokes an immune response, which cross-reacts” with a similar-looking protein on our pancreas such that when we attack the bug, our own organ gets caught in the cross-fire. Given this, what pancreatic proteins are type 1 diabetics self-attacking? In the 1980s, a protein was identified that we came to realize in the 1990s looked an awful lot like a certain mycobacterial protein. Mycobacteria are a family of bacteria that cause diseases like tuberculosis and leprosy, and, in one study, all newly diagnosed type 1 diabetic children were found to have immune responses to this mycobacterial protein. This didn’t make any sense as incidence of type 1 diabetes has been going up in the industrialized world, whereas TB and leprosy rates have gone down. However, there is one mycobacterial infection in farm animals that has shot up with the industrialization and globalization of animal agriculture: paratuberculosis (paraTB), which causes Johne’s disease in animals. Paratuberculosis is now recognized as a global problem for the livestock industry.

Weren’t there a dozen or so studies suggesting that “cow’s milk exposure may be an important determinant of subsequent type 1 diabetes” in childhood? Indeed. After putting two and two together, an idea was put forward in 2006: Could mycobacterium paratuberculosis from cattle be a trigger for type 1 diabetes? The idea was compelling enough for researchers put it to the test.

They attempted to test the association of Mycobacterium avium paratuberculosis (MAP), the full name for the bug, with type 1 diabetes by testing diabetics for the presence of the bacteria in their blood. Lo and behold, most of the diabetic patients tested positive for the bug, compared to only a minority of the healthy control subjects. This evidence of MAP bacteria in the blood of patients with type 1 diabetes “might provide an important foundation in establishing an infectious etiology,” or cause, for type 1 diabetes. “These results also might possibly have implications for countries that have the greatest livestock populations and high incidence of MAP concurrent with the highest numbers of patients with” diabetes, like the United States.

Johne’s is the name of the disease when farm animals get infected by MAP. The reason diabetes researchers chose to look at Sardinia, an island off the coast of Italy, is because paratuberculosis is present in more than 50 percent of Sardinian herds. Surpassing that, though, is the U.S. dairy herd. According to a recent national survey, 68 percent of the U.S. dairy herd are infected with MAP, especially those cattle at big, industrial dairies, as you can see at 3:33 in my video. Ninety-five percent of operations with more than 500 cows came up positive. It’s estimated the disease costs the U.S. industry more than a billion dollars a year.

How do people become exposed? “The most important routes of access of MAP to the [human] food chain appear to be contaminated milk, milk products and meat” from infected cattle, sheep, and goats. MAP or MAP DNA has been detected in raw milk, pasteurized milk, infant formula, cheese, ice cream, muscle and organ tissues, and retail meat. We know paraTB bacteria survive pasteurization because Wisconsin researchers bought hundreds of pints of retail milk off store shelves from three of the top U.S. milk-producing states and tested for the presence of viable, meaning living, MAP bacteria. They found that 2.8 percent of the retail milk tested came back positive for live paraTB bacteria, with most brands yielding at least one positive sample. If paraTB does end up being a diabetes trigger, then “these findings indicate that retail milk [in the United States] would need to be considered as a transmission vector.” Why hasn’t the public heard about this research? Perhaps because the industry is not too keen on sharing it. Indeed, according to an article in the Journal of Dairy Science: “Fear of consumer reaction…can impede rational, open discussion of scientific studies.”

Not only is MAP a serious problem for the global livestock industry, but it also may trigger type 1 diabetes, given that paraTB bacteria have been found in the bloodstream of the majority of type 1 diabetics tested who presumably are exposed through the retail milk supply as the bacteria can survive pasteurization. But what about the meat supply? MAP has been found in beef, pork, and chicken. It’s an intestinal bug, and unfortunately, “[f]aecal contamination of the carcass in the abattoir [slaughter plant] is unavoidable…” Then, unless the meat is cooked well-done, it could harbor living MAP.

In terms of meat, “ground beef represents the greatest potential risk for harboring MAP…[as] a significant proportion originates from culled dairy cattle,” who may be culled because they have paratuberculosis. These animals may go straight into the human food chain. There also exists greater prevalence of fecal contamination and lymph nodes in ground meat, and the grinding can force the bacteria deep inside the ground beef burger. As such, “given the weight of evidence and the severity and magnitude of potential human health problems, the precautionary principle suggests that it is time to take actions to limit…human exposure to MAP.” At the very least, we should stop funneling animals known to be infected into the human food supply.

We know that milk exposure is associated with type 1 diabetes, but what about meat? As I discuss in my video Meat Consumption and the Development of Types 1 Diabetes, researchers attempted to tease out the nutritional factors that could help account for the 350-fold variation in type 1 diabetes rates around the world. Why do some parts of the world have rates hundreds of times higher than others? Yes, the more dairy populations ate, the higher their rates of childhood type 1 diabetes, but the same was found for meat, as you can see at 2:07 in my video. This gave “credibility to the speculation that the increasing dietary supply of animal protein after World War II may have contributed to the reported increasing incidence of type 1 diabetes…” Additionally, there was a negative correlation—that is, a protective correlation that you can see at 2:26 in my video—between the intake of grains and type 1 diabetes, which “may fit within the more general context of a lower prevalence of chronic diseases” among those eating more plant-based diets.

What’s more, the increase in meat consumption over time appeared to parallel the increasing incidence of type 1 diabetes. Now, we always need to be cautious about the interpretation of country-by-country comparisons. Just because a country eats a particular way doesn’t mean the individuals who get the disease ate that way. For example, a similar study looking specifically at the diets of children and adolescents between different countries “support[ed] previous research about the importance of cow’s milk and [other] animal products” in causing type 1 diabetes. But, the researchers also found that in countries where they tended to eat the most sugar, kids tended to have lower rates of the disease, as you can see at 3:18 in my video. This finding didn’t reach statistical significance since there were so few countries examined in the study, but, even if it had and even if there were other studies to back it up, there are countless factors that could be going on. Maybe in countries where people ate the least sugar, they also ate the most high fructose corn syrup or something. That’s why you always need to put it to the test. When the diets of people who actually got the disease were analyzed, increased risk of type 1 diabetes was associated with milk, sugar, bread, soda, eggs, and meat consumption.

In Sardinia, where the original link was made between paraTB and type 1 diabetes, a highly “statistically significant dose-response relationship” was found, meaning more meat meant more risk, especially during the first two years of children’s lives. So, “[h]igh meat consumption seems to be an important early in life cofactor for type 1 diabetes development,” although we needed more data.

The latest such study, which followed thousands of mother-child pairs, found that mothers eating meat during breastfeeding was associated with an increased risk of both preclinical and full-blown, clinical type 1 diabetes by the time their children reached age eight. The researchers thought it might be the glycotoxins, the AGEs found in cooked meat, which can be transferred from mother to child through breastfeeding, but they have learned that paratuberculosis bacteria can also be transferred through human breast milk. These bacteria have even been grown from the breast milk of women with Crohn’s disease, another autoimmune disease linked to paraTB bacteria exposure.


For a deeper discussion of other possibilities as to why cow’s milk consumption is linked to this autoimmune destruction of insulin production, see Does Casein in Milk Trigger Type 1 Diabetes? and Does Bovine Insulin in Milk Trigger Type 1 Diabetes?.

If we don’t drink milk, though, what about our bone health? See my videos Long-Term Vegan Bone Health and Is Milk Good for Our Bones?.

The vast majority of cases of diabetes in the United States are type 2, though. Ironically, meat may also play a role there. See my videos Why Is Meat a Risk Factor for Diabetes? and How May Plants Protect Against Diabetes? for more information.

For more on the links between milk and diabetes, see my videos Does Casein in Milk Trigger Type 1 Diabetes? and Does Bovine Insulin in Milk Trigger Diabetes?. What about treating and preventing diabetes through diet? Check out How Not to Die from Diabetes and How to Prevent Prediabetes from Turning Into Diabetes.

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: