The gut microbiome plays an important role in many aspects of health, from digestion and immune function to metabolic balance and neurological processes. Several diseases have been associated with changes in the microbiome’s composition, including inflammatory bowel disease, colorectal cancer, obesity and mental health disorders. As links between gut microbes and disease grow stronger, scientists are now looking at the emerging connection between the gut and the heart.
Heart disease remains the leading cause of death globally. Factors such as smoking, high blood pressure, obesity and diabetes are known risk factors. But researchers are increasingly finding that the balance of microbes in our gut may shape how these risks develop — and how heart disease progresses. This newly recognised association, termed the “gut-heart axis”, has gained traction in recent years. It may help explain why diet and heart disease are so closely intertwined, and why what you eat matters so profoundly for long-term health.
Large studies show that people with cardiovascular disease have distinct gut microbiome profiles compared with healthy people. While no single “heart disease microbe” has been discovered, cardiovascular disease is consistently associated with reduced microbial diversity, loss of beneficial bacteria, and an overgrowth of microbes linked to inflammation. Microbial diversity refers to the variety and balance of different microbes living within the gut — and growing evidence suggests that a reduction in this diversity reflects deteriorating microbiome health, and may signal the onset of disease.
One recent paper examined results from 67 studies exploring the gut microbiome across several cardiovascular diseases, comparing over 6,000 patients with acute coronary syndrome, atrial fibrillation, coronary artery disease, heart failure or stroke with healthy people. It showed that people with cardiovascular disease consistently had lower levels of the beneficial fibre-fermenting bacteria Faecalibacterium — a finding that points toward the central role of diet and lifestyle in maintaining gut health.
Microbial Fingerprints of Heart Disease
Your gut microbes act as miniature factories that break down food components. In doing so, they produce hundreds of small molecules called metabolites, which can be absorbed through the intestine into the bloodstream. While some of these metabolites are beneficial, others can be harmful in excess.
One of the strongest links between the gut microbiome and heart disease involves a metabolite called TMAO — trimethylamine N-oxide. Certain gut bacteria convert nutrients found in red meat, eggs and dairy into a metabolite called trimethylamine, which the liver then processes into TMAO. High levels of TMAO in the blood have been associated with increased risk of heart attack, stroke and death from cardiovascular disease. Importantly, TMAO production varies between people depending on the type of microbes present in their gut — meaning two people can eat identical diets but produce very different amounts of this potentially harmful compound. It is one of the reasons why personalised nutrition is becoming an increasingly important field for researchers and clinicians alike.
But not all gut-derived metabolites are harmful. Some may actually protect the heart. A growing body of research is investigating indoles — compounds made when gut bacteria break down tryptophan, an essential amino acid found in protein-rich foods such as poultry, eggs, dairy and nuts. Tryptophan plays an important role in mood, sleep patterns and appetite. While the majority is absorbed directly by the body, a small fraction is broken down by gut bacteria and transformed into indole-derivatives — some of which appear to have powerful cardioprotective benefits.
One of the most promising is indole-3-propionate (IPA), produced mainly by the bacteria Clostridium sporogenes. Several studies have shown that people with higher blood levels of IPA have lower rates of type 2 diabetes and cardiovascular disease. IPA also strengthens the gut barrier, preventing harmful microbial products from leaking into the bloodstream — a mechanism that may prove central to the next generation of heart disease prevention strategies.
Prevention and Treatment
The discovery that gut microbes help shape cardiovascular risk is transforming how scientists think about prevention and treatment. Researchers are now exploring how microbial “fingerprints” could one day be used alongside known risk factors to identify people at risk long before symptoms appear.
In the future, beneficial gut microbes — probiotics — could be used therapeutically to slow cardiovascular disease progression or eliminate microbes known to contribute to disease onset. While this science is still emerging, it is clear that the gut microbiome should be viewed as part of the whole body system that shapes overall health.
It points toward a powerful idea: caring for your heart may start not just with what you eat, but with how your gut microbes process it.
Written by Fiona Newberry, Postdoctoral Research Associate, Department of Cardiovascular Sciences, University of Leicester.
