What Is TMAO, and Why Do You Want Less of It?

Updated July 2026

Here's one of the clearest examples of how your gut bacteria talk to your heart. When you eat certain animal products, the microbes in your gut produce a compound that appears to raise your risk of heart attack and stroke. It's called TMAO, and it's one of the most compelling reasons that what feeds your microbiome matters far beyond digestion.

What is TMAO and where does it come from?

It's a compound your gut bacteria make from nutrients in animal foods. When you eat choline (abundant in red meat, egg yolks, and full-fat dairy) and L-carnitine (found in red meat, plus some energy drinks and supplements), gut bacteria digest them and produce trimethylamine, or TMA. Your liver then converts TMA into trimethylamine N-oxide, TMAO. So TMAO isn't something you eat directly. It's manufactured inside you, by the specific community of bacteria your diet has cultivated.

Why is TMAO bad for your heart?

Because higher levels are linked to a higher risk of blood-clot events like heart attack and stroke. Elevated TMAO promotes clotting, in part by making blood platelets more prone to clumping. What makes it notable is that this link holds even after accounting for the usual risk factors, like blood pressure, cholesterol, and diabetes, and even after accounting for markers of inflammation. In one analysis of more than 2,000 people with heart disease, those with the highest TMAO levels had roughly a four-fold greater risk of dying over the following five years. Larger reviews since have reached the same conclusion: TMAO tracks consistently with cardiovascular events and death.

One honest caveat: most of the human evidence is associational. Animal studies point to TMAO directly causing harm, but in people it's hard to fully separate TMAO from everything else that comes with a meat-heavy diet, and TMAO levels are also affected by kidney function. So the fairest way to describe it is a risk marker with a plausible mechanism behind it, rather than a proven single cause. Either way, lower is better.

How do you lower your TMAO levels?

Eat less of the foods that feed its production, and more of the foods that suppress it. What to reduce: processed and unprocessed red meat (beef, pork, lamb, veal), full-fat dairy (whole milk, butter, cream cheese), egg yolks, and any energy drinks or supplements containing choline, phosphatidylcholine, or L-carnitine. What to increase: whole-food fiber and plant foods generally, which have been shown to significantly lower TMAO. Recent diet studies confirm the pattern; when red meat is the main protein, TMAO climbs, and when it's replaced with non-meat protein, TMAO falls.

Here's the fascinating part: your gut can forget how to make it.

People who switch to a fully plant-based diet gradually lose much of their ability to produce TMAO, and some barely make any at all, even if they try. Feed a steak, loaded with both choline and carnitine, to a committed vegan, and it has little effect on their TMAO. Why? Because over time, vegetarians and vegans cultivate a different community of gut bacteria, one that simply isn't equipped to churn out much TMAO. It's a striking demonstration that your microbiome adapts to what you habitually feed it, and that dietary change reaches all the way down to which chemical reactions your gut is even capable of running.

What's the takeaway?

TMAO is a vivid reminder of the intimate relationship between gut flora and heart health, and of how much downstream power your everyday food choices carry. Shifting toward a more plant-centered pattern lowers TMAO along with a long list of other cardiovascular risks. It's one more reason the plant-based, fiber-rich foundation behind Step One Foods is good for you. For the fuller story of how your gut shapes your health, start with what the gut microbiome is and why it matters.

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