A new paper says that altered gut microbiota in humans is associated with symptomatic atherosclerosis and stroke. 

The human body contains ten times more bacterial cells than human cells, most of which are found in the gut. These bacteria contain an enormous number of genes in addition to our host genome, and are collectively known as the gut metagenome. How does the metagenome affect health? It's unclear, other than that probiotic foods are a $30 billion placebo. But specifics are currently being addressed by researchers in metagenomic research. 

Researchers at Chalmers University of Technology and Sahlgrenska Academy, University of Gothenburg, now say that changes in the gut metagenome can be linked to atherosclerosis and stroke. They compared a group of stroke patients with a group of healthy subjects and found major differences in their gut microbiota. In particular, they showed that genes required for the production of carotenoids were more frequently found in gut microbiota from healthy subjects.

Carotenoids are a type of antioxidant, and it has been claimed for many years that they protect against angina and stroke. Thus, the increased incidence of carotenoid-producing bacteria in the gut of healthy subjects may offer clues to explain how the gut metagenome affects disease states. Carotenoids are marketed today as a dietary supplement and the market for them is huge, but clinical studies haven't shown any efficacy in protecting against angina and stroke.

Still, the healthy subjects also had significantly higher levels of a certain carotenoid in the blood than the stroke survivors, and so Jens Nielsen, Professor of Systems Biology at Chalmers, says probiotics may be the way to go, if they contain types of bacteria that produce carotenoids. Unsurprisingly, they have started a company, Metabogen, to make such a product. 

"Our results indicate that long-term exposure to carotenoids, through production by the bacteria in the digestive system, has important health benefits. These results should make it possible to develop new probiotics. We think that the bacterial species in the probiotics would establish themselves as a permanent culture in the gut and have a long-term effect."

"By examining the patient's bacterial microbiota, we should also be able to develop risk prognoses for cardiovascular disease", says Fredrik Bäckhed, Professor of Molecular Medicine at the University of Gothenburg. "It should be possible to provide completely new disease-prevention options".

When someone claims they can prevent disease with a food they are selling, hold onto your wallet. But it will probably be touted by Dr. Oz in six months.

Published in Nature Communications.