Gut-derived TMAO raises atrial fibrillation risk
What your gut bacteria produce reaches directly into your heart. A compound that the gut microbiome manufactures from certain foods appears to be linked to a higher risk of atrial fibrillation, a common and dangerous heart arrhythmia.
The compound is called TMAO, short for trimethylamine N-oxide. Gut bacteria produce TMAO from choline and L-carnitine, substances found mainly in red meat and eggs. TMAO enters the bloodstream and has previously attracted attention for its potential role in cardiovascular disease. Now new evidence, covered in the Fight Aging! newsletter, points to a link with atrial fibrillation (a heart rhythm disorder in which the upper chambers beat irregularly).
Atrial fibrillation is one of the most common arrhythmias in older adults and raises the risk of stroke and heart failure. The researchers found that higher blood TMAO levels were associated with an increased risk of developing this condition. Whether TMAO causes the disorder or is merely a marker of other risk factors has not yet been established.
Why gut bacteria affect the heart
The gut microbiome is a complex ecosystem that influences the metabolism of its host. TMAO illustrates how bacterial conversion of ordinary nutrients can yield compounds with potentially unfavourable effects. Inflammatory processes and changes in heart muscle cells have been proposed as intermediate mechanisms, but the precise pathway remains unclear.
The composition of the gut microbiome shifts with age. Older adults on average have a less diverse microbiome, which may influence TMAO production. This makes the TMAO-microbiome-heart axis particularly relevant from an ageing perspective.
What this means in practice
Diets rich in choline and L-carnitine, such as those high in red meat, increase TMAO production. More plant-based diets are associated with lower TMAO levels, though even here the data are observational. Direct dietary recommendations do not follow from this type of research; randomised trials are needed first.
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