Eating for Gut and Heart Health

A: We don’t know for sure, but some research suggests that keeping your gut healthy can be another means to protect against heart disease.

There’s a complex interplay between the trillions of microbes in our intestines and most of the systems in our bodies, including the vascular, nervous, endocrine, and immune systems, all of which are linked with cardiovascular health.

Since diet plays a significant role in the composition of gut microbiota, what you feed your gut can therefore affect heart health — for better and for worse.

One way the gut does this is with metabolites, substances the gut microbiota creates when breaking down food. One particular gut metabolite, trimethylamine (TMA), forms when gut microbes feed on choline, a nutrient found especially in red meat. In the liver, TMA gets converted to trimethylamine N-oxide (TMAO), a substance linked to forming artery-clogging plaque.

Research has shown that people with high TMAO levels in their blood are more likely to suffer a heart attack or stroke than those with lower levels. Since red meat is a main source of TMA, cutting back on consumption of red meat can theoretically reduce levels of TMAO.

In fact, a study in the September 2022 issue of Arteriosclerosis, Thrombosis, and Vascular Biology found that among nearly 4,000 people ages 65 and older, those who ate an average of 1.1 servings of red meat per day had a 22% higher risk of heart disease compared with those who ate less.

The researchers pointed out that about 10% of this added risk could be attributed to increased levels of TMAO as well as two other metabolites — gamma-butyrobetaine and crotonobetaine — which also are made by gut bacteria from components in red meat.

Fiber also helps support the gut and thus the heart. According to some estimates, fiber-rich diets can lower the risk of heart disease and stroke by as much as 30%. Fiber in the small intestine binds fat and cholesterol, decreasing absorption and lowering blood cholesterol levels.

But the gut’s microbiota also helps out. Fiber gets broken down by bacteria in the colon to form short-chain fatty acids. These compounds interact with specific receptors on cells that regulate blood pressure, better control blood sugar and body weight in people with diabetes, and dampen inflammation — all of which can improve heart health.

It’s unclear whether eating other foods that improve gut microbiota — for example, probiotics (beneficial bacteria) found in yogurt and fermented foods (sauerkraut, miso, tempeh) — can also support heart health.

Right now, the best advice for maintaining both gut and heart health is to follow a diet that emphasizes plant-based foods.

Howard LeWine, M.D., is an internist at Brigham and Women’s Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, please visit www.health.harvard.edu.

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