Should we be concerned about high-choline plant foods such as broccoli producing the same toxic TMAO that results from eating high-choline animal foods such as eggs?

Choline- and carnitine-rich foods—meat, eggs, and dairy—can be converted by our gut flora into trimethylamine, which in our livers is then turned into TMAO, a toxic compound that may increase our risk of heart failure, kidney failure, and atherosclerosis, or heart attacks and strokes. The good news, though, is that this “opens up exciting new nutritional and interventional prospects” for prevention, as I discuss this in my video How to Reduce Your TMAO Levels.

Okay, so how do we do it? Well, if our gut bacteria can take meat, dairy, and eggs and turn them into TMAO, all we have to do is…destroy our gut flora! We could give people antibiotics to eliminate the production of TMAO. However, that could also kill our good bacteria and “facilitate the emergence of antibiotic-resistant bacterial strains.”

What about probiotic supplements? Maybe if we add good bacteria, they will crowd out the ones that take the meat, egg, and dairy compounds and turn them into the TMA that our liver turns into TMAO. But, that doesn’t work. Adding good bacteria doesn’t seem to get rid of the bad. What if we added new bacteria that could somehow siphon off the TMA made by the bad bacteria? Well, there’s a bacterium inside the guts of cows and sheep that turns trimethylamine into methane. Could we use that bacterium to get rid of some of the trimethylamine from our gut, like a cow fecal transplant? There’s a problem with that. If it didn’t take, you’d have to keep giving it to people: “Continuous administrations may be necessary if subjects do not become colonized.” So, might the fact that Consumer Reports found fecal contamination in every sample of beef it tested be a good thing? No. Methane-producing bacteria may be able to eat up our TMAO, but, unfortunately, these bacteria may be associated with a variety of diseases, from gum disease down to colorectal cancer, as you can see at 2:15 in my video.

If antibiotics and probiotics aren’t going to work to prevent gut bacteria from taking meat, dairy, and eggs and turning them into the trimethylamine, which our liver makes TMAO out of, I guess we have no choice but to cut down on…our liver function!

That was the billion-dollar answer to cholesterol. The same foods—meat, dairy, and eggs—raise our cholesterol, but dietary change isn’t very profitable. So, the drug industry developed statin drugs that cripple the liver’s enzyme that makes cholesterol. Could “pharmacologic inhibition” of the enzymes in our liver that make TMAO “potentially serve as a therapy for CVD [cardiovascular disease] risk reduction”? Trimethylaminuria is a genetic condition in which this enzyme is naturally impaired, in which there is a build-up of trimethylamine in the bloodstream. The problem is that trimethylamine is so stinky it makes you smell like “dead fish.” So, “given the known adverse effects…from sufferers of fish odor syndrome, the untoward odorous side effects of inhibiting this enzyme make it a less attractive [drug] target.”

Do we have to choose between smelling like dead fish or suffering from heart and kidney disease? If only there were some other way we could stop this process from happening. Well, what do those with trimethylaminuria often do to cut down trimethylamine levels? They stop eating animal products.

About a third of those who complain of bad body odor despite good personal hygiene test positive for the condition, but reducing or eliminating meat, egg, and dairy intake can be a real lifesaver. But, given what we now know about how toxic the end product TMAO can be for normal people, cutting down on animal products may not just save the social lives of people with a rare genetic disorder, but help save everyone else’s actual lives.

The “simplest point of intervention” is to simply limit the consumption of foods rich in choline and L-carnitine, which “can be an effective strategy to limit circulating TMAO.” But, wait! We could always try to genetically engineer a bacterium that eats up trimethylamine, but “the simplest and safest recommendation” may just be to eat more healthfully. You can completely eliminate carnitine from the diet, since our body makes all we need, but choline is an essential nutrient so we do need some. Thankfully, we can get all we need in fruits, vegetables, beans, and nuts. “However excess choline, such as that found in eggs, may be worth avoiding.”

Need we worry about high-choline plant foods, like broccoli? Consumption of cruciferous vegetables is associated with a significantly longer life and less cardiovascular disease mortality, as you can see at 5:34 in my video. To see what was going on, researchers took the vegetable highest in choline, brussels sprouts, and had people eat two cups a day for three weeks. What happened? Their TMAO levels actually went down. It turns out that brussels sprouts appear to naturally downregulate that TMAO liver enzyme—not enough to make you stinky, but just enough to drop TMAO.

And, people who eat completely plant-based may not make any TMAO at all—even if you try. You can give a vegan a steak, which contains both choline and carnitine, and there will not even be a bump in TMAO because vegetarians and vegans have different gut microbial communities. If we don’t eat steak, then we don’t foster the growth of steak-eating bacteria in our gut. So forget the cow—how about getting a fecal transplant from a vegan? From a TMAO standpoint, we may not have to eat like a vegan as long as we poop like one.

Can you sense my frustration as I read paper after paper proposing those ridiculous (but profitable!) answers when the safe, simple, side-effect-free solution was staring them in the face the whole time? It makes me think of so many parallels, not the least of which are:

For more on TMAO, the “smoking gun” of diet-microbiome-disease interactions, see:

In health,

Michael Greger, M.D.

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