Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
“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% of the DNA in our body is human. The rest is in our microbiome—the microbes that we share with this walking community we call our body. What do they do?
Our “[g]ut microbiota [our gut bacteria microbiome] serve as a filter for our largest environmental exposure—what we eat. Technically speaking, food is a foreign object that we take into our bodies [by the pound] every day.” “And, the microbial community within each of us significantly influences how we experience [those meals].” “Hence, our metabolism and absorption of food occurs through [this] filter of bacteria.”
But, if we eat a lot of meat, poultry, fish, milk, cheese, eggs, we can foster the growth of bacteria that convert the choline and carnitine in these foods into TMA—trimethylamine, 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 over 40 years. But, that was way before we learned about the heart disease connection. Why were they 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 alone (like PCBs), children probably shouldn’t eat more than like five servings a month of meats like beef, pork, or chicken, combined. But, what about cancer and eggs?
Studies going back to the 70s hinted at a correlation between eggs and colon cancer. But, that was just based on so-called ecological data, showing that countries that ate more eggs tended to have higher cancer rates. But, that could be due to a million things, right? It needed to be put to the test.
This started in the 80s, and by the 1990s, 15 studies had been published: ten suggesting “a direct association” between egg consumption and colorectal cancer, and five showing “no association.” By 2014, there were dozens more studies 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 suggests that “egg[s] might be involved [more] in the promotional [stage of cancer growth—accelerating cancer growth, rather than] initiating [the cancer in the first place].”
Which brings us to 2015. Maybe it’s the TMAO, made from the choline in meat and eggs, that’s promoting cancer growth. And, 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 “TMAO [levels] may serve as a potential predictor of increased colorectal cancer risk.”
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 like “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 they may not be able to make TMAO, even if we try. “The theory of “you are what you eat” [is] finally…supported by scientific evidence.”
We may not have to eat healthy for long, though. Soon, we may yet be able to “‘drug the microbiome’” as a way of “promoting cardiovascular health.”
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