TMAO, short for trimethylamine oxide, was identified when the blood of patients who had experienced a heart attack or stroke was compared to the blood of those who hadn’t. The more TMAO people had in their blood, the more likely they were to go on to suffer a heart attack, stroke, or otherwise die prematurely. Where does TMAO come from? Just as short-chain fatty acids are produced by good bacteria in our gut when we eat fiber, TMAO originates from bad bacteria in our gut when we eat lots of choline (concentrated in eggs, but also lecithin supplements) or carnitine (concentrated in meat, but also some energy drinks).
If you eat eggs or meat, you get a bump in TMAO levels within hours, unless you recently took antibiotics that wipe out your gut flora. In that case, it can be weeks before your bad bacteria grow back. Alternately, you can prevent the growth of these bad bacteria by not feeding them in the first place. Feed a vegan a steak, and they make virtually no TMAO, presumably because they hadn’t been fostering the growth of steak-eating bacteria.
The egg and beef industries funded a joint study that showed TMAO levels were lowest after eating the non-egg and non-beef control food: fruit. Even relatively choline-rich plant foods don’t seem to cause a problem. For example, two ounces of pistachios every day actually seemed to cause a reduction in levels.
TMAO may help explain why those who eat more plant-based diets are more protected from heart disease. What about obesity? Obese individuals seem to churn out more TMAO, so does avoiding carnitine and choline-rich foods help with weight loss? Subjects with greater reductions in carnitine and choline were significantly more likely to experience weight loss and waist slimming, while those with increases in carnitine or choline were about twice as likely to fail to lose weight over a two-year period.
The information on this page has been compiled from Dr. Greger’s research. Sources for each video listed can be found by going to the video’s page and clicking on the Sources Cited tab. References may also be found at the back of his books.
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