How to Develop a Healthy Gut Ecosystem

As Iíve 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 TMAOótrimethylamine oxideóin 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? 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 theyíre not eating any meat, eggs, or dairy. But, even if vegans eat a sirloin, almost no TMAO is made. Why? Presumably, they donít have steak-eating bacteria in their guts. Indeed, it was found that no TMAO is produced if you donít have TMAO producing bacteria in your gut. If you donít regularly eat meat, then youíre 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 donít know how rapidly gut bacteria shift after a shift in our dietóbut 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, itís 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 ďdemonstrated to have a profound influence on human metabolism,Ē 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. At 2:43 in my video, youíll 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. Itís 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.

In health,
Michael Greger, M.D.

PS: If you havenít yet, you can subscribe to my free videos†here†and watch my live, year-in-review presentationsó2015:†Food as Medicine: Preventing and Treating the Most Dreaded Diseases with Diet, and my latest, 2016:†How Not to Die: The Role of Diet in Preventing, Arresting, and Reversing Our Top 15 Killers.

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Martin H
Martin H4 months ago

All I know about my gut is that it hangs over my belt!

Janis K
Janis K4 months ago

Thanks for sharing.

Mike R
Mike R4 months ago


Peggy B
Peggy B4 months ago


Barbara S
Barbara S4 months ago

Thanks for sharing

heather g
heather g4 months ago

so many people are vegan or vegetarian, it wouldn't hurt to know how this has affected statistics of heart disease, etc.

Christine Stewart
Christine Stewart4 months ago

I am mostly vegan, so I hope I have good bacteria in my gut!

Jessica K
Jessica K4 months ago

We have a really long digestive track so it seems to make sense that plants would be a better resident there than animal products. Carnivores like cats have a shorter digestive track. Thanks.

Dennis Hall
Dennis H4 months ago


Tabot T
Tabot T4 months ago

Thanks for sharing!