What if some of the chemistry controlling your cholesterol isn't produced by your own body, but by bacteria living in your gut?

It sounds extraordinary, but a new study published in Nature has uncovered a fascinating connection between intestinal bacteria, cholesterol metabolism and the development of atherosclerosis. Researchers discovered that a common gut bacterium can manufacture a fatty acid capable of blocking the same enzyme targeted by statin medications. Even more remarkably, this compound substantially reduced the accumulation of arterial plaque in experimental mice.

It's early research, and we're certainly not at the point of replacing cholesterol medication with probiotics. Nevertheless, the discovery reveals something important about the relationship between our gut microbiome and cardiovascular health.

Your Gut and Liver Are Constantly Communicating

When we think about cholesterol, we usually focus on what we're eating and how much is circulating in our blood. But the liver is central to cholesterol regulation, both manufacturing cholesterol and removing LDL particles from circulation.

One particularly important enzyme is HMG-CoA reductase, which controls a key step in cholesterol synthesis. Statin medications inhibit this enzyme, reducing cholesterol production in the liver and encouraging the liver to increase its LDL receptors. These receptors remove LDL particles from the bloodstream, lowering circulating LDL cholesterol.

This matters because LDL particles can become trapped within arterial walls, contributing to the development of atherosclerosis. Over time, retained lipoproteins trigger inflammatory processes involving immune cells, cholesterol accumulation and the formation of plaques. These plaques can eventually contribute to heart attacks and strokes.

What's particularly interesting is that the liver doesn't regulate cholesterol in isolation. It receives a constant stream of compounds from the intestines through the portal circulation, including substances produced by gut bacteria.

Some microbial metabolites influence bile-acid metabolism, while others interact with receptors involved in glucose regulation, inflammation and lipid metabolism. The new research suggests that certain gut bacteria may go a step further and directly influence cholesterol synthesis itself.

The Bacterial Compound That Acts on a Statin Target

The researchers investigated Bacteroides uniformis, a species of bacterium found in the human gut. In mice genetically predisposed to atherosclerosis, administering this organism improved blood lipid profiles and reduced the development of arterial plaques.

They subsequently identified a compound called pentadecanoic acid, or C15:0, as an important part of the mechanism.

C15:0 is an odd-chain saturated fatty acid, meaning its carbon structure contains fifteen carbon atoms. The researchers demonstrated that it could inhibit HMG-CoA reductase, the same enzyme targeted by statins.

In experimental mice, administering C15:0 reduced atherosclerotic plaque burden by approximately 50%. The researchers also observed reduced cholesterol synthesis and increased LDL receptor expression in the liver, providing a plausible explanation for the improvement in circulating lipids.

The discovery is particularly interesting because it connects three separate biological systems: microbial metabolism in the gut, cholesterol regulation in the liver and plaque development in the arteries.

Rather than simply identifying an association between gut bacteria and heart disease, the investigators uncovered a specific molecule and a potential mechanism through which it could influence cardiovascular physiology.

Your Gut Bacteria Are Producing Far More Than You Think

Our intestinal microorganisms are essentially tiny biochemical factories. They transform components of our diet into compounds that can interact with human tissues, influence cellular signalling and alter aspects of metabolism.

One familiar example is the production of short-chain fatty acids, including butyrate and propionate, when gut bacteria ferment certain dietary fibres. These compounds can influence intestinal function, immune signalling and metabolic processes.

Another example involves bile acids. The liver manufactures bile acids from cholesterol to help digest dietary fats, but intestinal bacteria can modify them into different molecules. Some of these interact with receptors such as FXR and TGR5, which participate in the regulation of lipid metabolism, glucose handling and inflammatory signalling.

The new C15:0 discovery adds another possible pathway to this relationship. Instead of influencing cholesterol metabolism through a complex signalling cascade, a bacterial product appears capable of directly inhibiting an enzyme involved in cholesterol synthesis.

This helps explain why scientists are increasingly interested in what our gut bacteria do, rather than simply which species are present.

Two people may harbour similar bacterial species but produce different quantities of microbial metabolites, depending upon their diets, microbial communities and wider metabolic environments.

Does This Mean We Should Be Taking C15:0 Supplements?

Not so fast.

Although the results are impressive, the reduction in arterial plaque was demonstrated in mice, not humans. Animal models provide valuable information about biological mechanisms, but they cannot establish whether a treatment will prevent cardiovascular disease in people.

C15:0 is also found in certain foods, particularly dairy fat, and has previously attracted interest in nutritional epidemiology. However, finding that a bacterial form of C15:0 influences cholesterol metabolism does not mean eating more dairy fat will lower LDL cholesterol or protect against heart disease.

Nor does it establish that C15:0 supplements are effective or safe for cardiovascular prevention.

The important questions now concern whether gut bacteria produce sufficient amounts of this fatty acid in humans to influence cholesterol synthesis, how much reaches the liver and whether manipulating the pathway produces meaningful improvements in cardiovascular outcomes.

Until those questions are answered, the findings should be viewed as a promising mechanistic discovery rather than a new treatment recommendation.

What Does This Mean for the Way We Eat?

We don't yet know whether particular dietary changes can reliably increase the production of C15:0 by gut bacteria. But the research reinforces a broader principle: diet influences cardiovascular health through more pathways than we once appreciated.

The foods we eat help shape the intestinal environment, affecting which microorganisms thrive and what compounds they produce. Dietary fibres and plant-derived compounds can influence microbial metabolism, although the resulting effects vary considerably between individuals.

For now, the strongest nutritional evidence for cardiovascular prevention continues to support dietary patterns rich in vegetables, fruits, legumes, whole grains, nuts and other fibre-containing plant foods, alongside appropriate management of established cardiovascular risk factors.

Soluble fibres, for example, can lower LDL cholesterol through mechanisms involving intestinal cholesterol and bile-acid handling. These benefits are supported by human clinical evidence, unlike the proposed cardiovascular effects of microbial C15:0, which remain experimental.

The exciting possibility is that future research may identify additional microbial pathways through which diet influences cholesterol metabolism, potentially opening the door to more targeted nutritional interventions.

The Bigger Picture

The most interesting thing about this discovery isn't necessarily that gut bacteria can produce a compound resembling the action of a cholesterol-lowering drug. It's what that tells us about human physiology.

Our metabolism doesn't operate independently of the trillions of microorganisms living inside us. Those organisms produce an enormous variety of molecules, some of which can interact with the liver, immune system and cardiovascular system.

The discovery that a bacterial fatty acid can inhibit a key enzyme in cholesterol synthesis is a remarkable example of that relationship.

Whether it eventually leads to a useful treatment remains uncertain. But it reinforces an increasingly important idea in nutritional medicine: to understand how diet influences health, we need to understand not only what we eat, but what our gut bacteria do with it.

References

Yin, C. et al. (2026) ‘A gut microbial odd-chain fatty acid alleviates atherosclerosis in mice’, Nature. https://doi.org/10.1038/s41586-026-11142-x

Yamauchi, Y., Sharpe, L.J. and Brown, A.J. (2026) ‘Balancing cholesterol metabolism in the liver and gut: perspectives in health and disease’, Nature Reviews Gastroenterology & Hepatology, 23, pp. 395–410. https://doi.org/10.1038/s41575-025-01168-3

Abavisani, M. et al. (2026) ‘Gut microbiota–cholesterol crosstalk in cardiovascular diseases: mechanisms, metabolites, and therapeutic modulation’, Nutrition & Metabolism, 23, article 4. https://doi.org/10.1186/s12986-025-01051-7