The March Nutrition Society Paper of the Month is from Proceedings of the Nutrition Society and is entitled ‘The way to a man’s heart is through his gut microbiota’ – dietary pro- and prebiotics for the management of cardiovascular risk.

It’s no secret that diet plays an important role in cardiovascular disease (CVD) risk. Regulatory agencies from around the world recommend we eat more fruit, vegetables and whole-grain cereals or complex carbohydrates for their ability to protect against chronic diseases like CVD. They also recommend we limit our consumption of red meat and saturated fat, which epidemiological studies show can increase CVD risk. However, we still do not fully understand how these foods or dietary habits work in terms of determining disease risk.

Recent studies showing that certain probiotic bacteria can lower blood cholesterol levels by inhibiting fat absorption hint that deep within the darkest secrets of the gut, or rather the gut microbiome, lie answers to dietary protection from chronic disease. In this review, we present current evidence supporting a mechanistic role for the gut microbiome, or the 100 trillion bacteria which inhabit our intestines, in both dietary protection from CVD and conversely, in production of toxic metabolites which cause CVD. It appears that not only is the balance of bacteria altered in CVD and associated diseases like obesity and diabetes, but that these aberrant bacterial profiles may play an active pathological role by producing toxic metabolites from compounds found in red meat. Conversely, the balance of bacteria in the gut, and their metabolic output readily responds to dietary fiber and plant polyphenols.

Indeed it appears that when exposed to a plentiful supply of fermentable fiber through foods like fruit, vegetables, whole grain cereals and prebiotics, the “beneficial” gut bacteria become dominant, increasing in relative abundance and inhibiting some of the more harmful bacterial activities associated with protein fermentation. Although not a new notion, this regulatory role of carbohydrate fermentation to “switch off” production of toxic metabolites produced when gut bacteria metabolize compounds like choline and L-carnitine, has recently been demonstrated in large scale multidisciplinary clinical studies in people with CVD. Other studies are expanding our understanding of probiotics and prebiotics, providing clear demonstrations of cause and effect relationships, and also, providing an anthropological basis for prebiotics, showing that prebiotics were not just an invention of the food industry but foods which mediate a fundamental biological process shared with certain whole grain cereals, fruit and vegetables and even red wine, and capable of improving human health through selectively changing ratios and metabolism of gut bacteria.

Unfortunately, our modern Western-style diet appears to be denuded of these fermentable fibers, prebiotics, probiotics, and polyphenols, and we suffer their absence through increased CVD risk.  In this review we propose that microbiota modulation may be at the base of healthy eating guidelines, explaining some of the health effects associated with fruit, vegetables and whole grain cereals. By combining evidence from the most recent “omics” level investigations with key observations on dietary regulation of CVD risk going back more than 40 years, we bring together functional foods and whole plant foods to help us explain why indeed one way to improve heart health may in fact lie through improved gut microbiome health.

This paper is freely available for one month via the following link: journals.cambridge.org/ns/mar14

Nutrition Society Paper of the Month

Each month a paper is selected by one of the Editors of the five Nutrition Society Publications (British Journal of Nutrition, Public Health Nutrition, Nutrition Research Reviews, Proceedings of the Nutrition Society and Journal of Nutritional Science). This paper is freely available for one month.