Heart disease is the leading cause of death in India. Not cancer, not infections, cardiovascular disease kills more Indians than anything else, and it’s hitting us earlier than almost any other population. The average age of a first heart attack in India is 53, about a decade younger than in Western countries.
We know the usual suspects: smoking, sedentary lifestyle, high blood pressure, diabetes, genetics. But there’s a player in this story that most cardiologists aren’t yet talking about during your check-up, the trillions of bacteria living in your gut.
TMAO: the molecule connecting your gut to your arteries
The strongest link between gut bacteria and heart disease runs through a molecule called trimethylamine N-oxide, or TMAO. The story of how it’s made is a neat example of how your diet, your bacteria, and your organs work together, sometimes against you.
When you eat foods rich in choline, carnitine, or lecithin (found abundantly in red meat, eggs, and some fish) certain gut bacteria convert these nutrients into trimethylamine (TMA). TMA then travels through the portal vein to your liver, where an enzyme converts it into TMAO.
TMAO promotes atherosclerosis through several mechanisms. It increases cholesterol deposition in arterial walls, promotes foam cell formation (the fatty cells that build up plaques), reduces reverse cholesterol transport (your body’s way of clearing excess cholesterol), and enhances platelet reactivity, which increases clotting risk.
A landmark study from the Cleveland Clinic, published in the New England Journal of Medicine, showed that higher blood levels of TMAO were associated with increased risk of major cardiovascular events (heart attack, stroke, and death) independent of traditional risk factors. Meaning even after accounting for cholesterol levels, blood pressure, and diabetes, TMAO still predicted who would have a cardiac event.
From an Indian perspective, there’s a further wrinkle. The specific bacteria in your gut determine how much TMA (and therefore TMAO) you produce from the same food. Two people eating the same amount of eggs for breakfast can produce very different TMAO levels based purely on their gut microbial composition. Some people’s gut bacteria convert choline to TMA efficiently; others’ bacteria don’t. This is one of the reasons why dietary studies on eggs and heart disease have been so contradictory, the effect depends partly on which bacteria are doing the processing.
Bile acids: your gut bacteria’s second job in heart health
Your liver produces bile acids to help digest fats. After doing their job in the small intestine, most bile acids are recycled back to the liver. But gut bacteria modify this process substantially.
Certain bacteria (particularly species of Clostridium, Lactobacillus, and Bifidobacterium) transform primary bile acids into secondary bile acids through a process called deconjugation and dehydroxylation. These secondary bile acids don’t just help with fat digestion. They activate receptors called FXR and TGR5, which regulate cholesterol metabolism, glucose handling, and inflammatory pathways.
When your gut microbiome is healthy and diverse, this bile acid recycling system works well, keeping cholesterol metabolism balanced. When it’s disrupted (through poor diet, a ntibiotic use, or chronic stress) bile acid metabolism goes off track, and cholesterol handling suffers.
This matters enormously for the millions of Indians taking statins. Statins lower cholesterol production in the liver, but they don’t address the gut-mediated bile acid pathways that also influence cholesterol levels. Some researchers believe that individual variations in response to statins (why they work brilliantly for some people and poorly for others) may partly be explained by differences in gut microbiome composition and bile acid metabolism.
Your liver produces bile acids to help digest fats.
Inflammation: the link in between
Cardiovascular disease is, at its core, an inflammatory condition. Atherosclerotic plaques aren’t just deposits of cholesterol: they’re sites of chronic inflammation in arterial walls.
And gut bacteria are major regulators of systemic inflammation. We’ve covered this in other contexts, but it bears repeating here: when the intestinal barrier becomes more permeable, bacterial endotoxins (lipopolysaccharides, or LPS) leak into the bloodstream. This triggers a low-grade inflammatory response that affects the entire body, including the cardiovascular system.
Studies have found that people with coronary artery disease have higher blood levels of LPS and markers of intestinal permeability compared to people with healthy hearts. Their gut microbiomes also look different, specifically, they tend to have fewer anti-inflammatory species like Faecalibacterium prausnitzii and Roseburia and more pro-inflammatory species.
For Indians, this inflammatory pathway has particular relevance. South Asians have higher levels of lipoprotein(a) and C-reactive protein (markers of inflammation and cardiovascular risk) compared to most other ethnic groups. While genetics plays a role, the gut microbiome’s contribution to systemic inflammation may be an underappreciated factor.
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Blood pressure and the gut
Emerging research suggests that gut bacteria also influence blood pressure, the other major cardiovascular risk factor. SCFAs produced by fibre-fermenting bacteria (butyrate, propionate, and acetate) interact with specific receptors in blood vessels and kidneys that help regulate blood pressure.
A study in the European Heart Journal found that people with hypertension had significantly less diverse gut microbiomes compared to people with normal blood pressure. The hypertensive patients had lower levels of SCFA-producing bacteria, the same species that thrive on dietary fibre from foods like whole grains, dal, and vegetables.
This creates an interesting connection. The traditional Indian diet, rich in legumes, whole grains, and vegetables, feeds exactly the bacteria that produce blood pressure-regulating SCFAs. The modern urban Indian diet, increasingly dominated by refined carbohydrates and processed food, starves these bacteria. The rise in hypertension across India correlates, at least in part, with the same dietary shifts that are reshaping our gut microbiomes.
Emerging research suggests that gut bacteria also influence blood pressure, the other major cardiovascular risk factor.
Putting it together
The gut-heart connection adds a new dimension to cardiovascular risk management. Your gut bacteria influence TMAO production, bile acid metabolism, systemic inflammation, and possibly blood pressure, all major factors in heart disease.
Keep taking your prescribed medications and tracking your cholesterol. But cardiovascular risk has more moving parts than most standard cardiology visits cover and what’s living in your gut is one of them. Eating diverse fibres, maintaining microbial diversity, and cutting back on the processed food that feeds inflammatory species is a meaningful addition to standard heart disease prevention, not a replacement for it.
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