One strategy recommended by doctors for people to combat high blood pressure is to increase the amount of fiber in their diet because fiber has been shown in tests to provide a protective benefit. But by looking at the glass half empty instead of half full researchers have discovered a low-fiber diet may actually be a cause of high blood pressure.
Scientists at Monash University in Australia have found mice fed a low-fiber diet were more predisposed to high blood pressure. They also performed fecal transplants on mice bred without gut microbes and only those given microbes from mice fed a low-fiber diet developed high blood pressure.
High blood pressure is the most common risk factor for cardiovascular disease and can lead to a heart attack or stroke. If not regulated, it can cause the arteries and muscles of the heart to harden and the kidneys to not function properly due to arterial stiffening.
"High blood pressure continues to be a major risk factor for cardiovascular death," said lead study author Dr. Francine Marques. "A diet poor in fiber is associated with prevalence of high blood pressure, but this study is changing the concept of fiber intake being only protective: lack of fiber can actually contribute to high blood pressure and cardiovascular disease, and this happens via the gut microbiota."
The results of the study were published in the journal Circulation. Mice were fed diets of high or low resistant starches. Resistant starches are a kind of prebiotic fiber that resists digestion until it passes to the large intestine where it feeds beneficial bacteria.
"The study is significant," said professor David Kaye, Director of Cardiology at Alfred Hospital, "because it identifies for the first time, how dietary fiber directly regulates heart and blood vessel health. One of the most unique findings of the study is that the bacterial profile of the gut, called the gut microbiome, is closely associated with blood pressure and this link is the result of chemicals released by gut bacteria into the circulation."
Kay said while it was known a high-fiber diet provides protective benefits the mechanism was uncertain.
It was found when resistant starches reach the large intestine, metabolites called short-chain fatty acids (SCFAs) are released through the process of microbial fermentation. Mice in the study that were given SCFAS had their blood pressure lowered and their cardiovascular health improved even in the absence of prebiotic fiber.
"The findings reinforce the need for a diet high in fiber and also point to new potential targets for the prevention and treatment of cardiovascular disease," Dr. Marques said.