Heart and Circulation

What Gut Bacteria Have to Do With the Heart

Heart disease is explained through cholesterol, blood pressure, smoking and weight, and those explanations are correct. What they leave out is that some foods only raise risk after gut bacteria have worked on them first. The same meal, eaten by two people, produces different amounts of a harmful compound depending on which bacteria are doing the digesting. That adds a pathway running alongside the familiar ones rather than replacing them, and it has been measured in tens of thousands of people.

A compound, a set of risk factors, and a rhythm

The compound is trimethylamine N-oxide, usually shortened to TMAO. Gut bacteria break down nutrients found in red meat and eggs, releasing a precursor that the liver converts into TMAO, which promotes fatty deposits in artery walls. Researchers measured it in 4,007 adults and followed them for three years. Higher levels predicted more heart attacks, strokes and deaths, after adjusting for blood pressure, cholesterol, diabetes, smoking and existing artery disease. Vegans and vegetarians given the same precursor produce substantially less of it, because years of eating differently left them with bacteria less able to make it.

The risk factors themselves are also partly shaped by bacteria, though selectively. In 893 people from a Dutch cohort, gut bacteria explained about 6% of the differences between people in blood triglycerides and about 4% in HDL cholesterol, while explaining almost nothing about LDL cholesterol. That selectivity is what makes it look like real biology rather than statistical noise.

Heart rhythm is the third area. A systematic review of 14 studies covering 2,479 people found the gut bacteria of those with an irregular heartbeat differing consistently from everyone else's, with a plausible route running from a leakier gut wall through inflammation to the electrical properties of heart tissue.

Source: Intestinal microbial metabolism of phosphatidylcholine and cardiovascular risk

Source: The Gut Microbiome Contributes to a Substantial Proportion of the Variation in Blood Lipids

Source: Association of gut microbiome dysbiosis with the progression of atrial fibrillation: A systematic review

What this means for you

Chest pain, breathlessness on exertion, or a racing or irregular pulse need prompt medical assessment, and blood pressure checks, cholesterol testing and prescribed medication remain the parts of heart care with the strongest evidence behind them. In addition, the research above shows gut bacteria converting certain nutrients into a compound that predicts heart attacks and strokes across tens of thousands of people. They also account for a measurable share of the differences between people in blood fats. A varied, plant-rich diet supports the same gut bacteria this research ties to producing less of that compound and to steadier blood fats. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.

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The panels on this page cover three different kinds of connection, and the evidence differs for each.

Blocked arteries concern one compound gut bacteria manufacture from food, with the most complete chain of evidence in this category. Heart disease concerns how much of the variation in standard risk factors bacteria account for, and is notable for what they don't affect as much as what they do.

Irregular heartbeat concerns inflammation reaching heart tissue and changing how it conducts electrical signals.

Use the panels on this page to find the one relevant to you.