How pre-diet fasting can reshape the microbiome and improve blood pressure
Two new studies examining the relationship between fasting and the microbiome offer new insight into how the makeup of our gut bacteria can be reshaped by short-term dietary changes, and how this can benefit cardiovascular health. Research suggests that fasting is not only beneficial for reshaping the microbiome, but a small fast before starting a new diet can amplify the beneficial effects of the diet.
A number of previous studies have pointed out that the community of bacteria living in our gut plays a major role in how the foods we eat influence our overall health. A pair of studies from last year, for example, found significant associations between diet, gut microbiome makeup, and healthy aging.
Fasting before the DASH diet
Recently published research now offers more granular information on these relationships, examining how dietary interventions, particularly fasting, can catalyze improvements in blood pressure via changes in the microbiome. The first study, published in the journal Nature communications, demonstrated how short-term fasting provided sharp improvements in blood pressure when followed by a longer-term Mediterranean diet.
One of the first treatments often offered to patients with hypertension is a diet intervention called DASH (Dietary Approach to Stop Hypertension). The DASH diet is an effective first-line treatment for hypertension, but it is still unclear exactly how it directly improves blood pressure. It is assumed that the dietary modifications of the the microbiome could be at the origin the improvements.
To study this hypothesis, a team of researchers recruited 71 subjects with hypertension. The cohort was randomly assigned to two groups, both tasked with following the DASH diet for three months. One group was also tasked with a five-day fast before the DASH diet.
By tracking changes in immune biomarkers and microbiome, researchers found greater improvements in blood pressure in the cohort preceding their dietary change with a period of fasting. Interestingly, the immune and microbiological changes observed in the fasting cohort were significantly different from those detected in volunteers only following the DASH diet.
Researchers hypothesize that the fasting diet can rapidly alter the makeup of the microbiome and increase the availability of short-chain fatty acids. This short-term change could subsequently alter the way the body responds to the DASH diet.
“Body mass index, blood pressure and the need for antihypertensive drugs remained lower over the long term in volunteers who started a healthy diet with a five-day fast,” notes Dominik MÃ¼ller, one of the researchers working about the project.
The microbiome link
Another recently published study, led by researchers at Baylor College of Medicine, aimed to better understand how gut microbes can influence blood pressure. The researchers also wondered if this result could be achieved without fasting, either by a dietary supplement or by directly manipulating the composition of the microbiome.
The researchers conducted a series of studies using a particular animal model designed to study hypertension, known as SHRSP rats (spontaneously hypertensive subjects with stroke). The first test was to determine if the changes in the microbiome induced by fasting resulted in an improvement in blood pressure.
For nine weeks, a group of SHRSP rats were fed every other day. At the end of this period, the intermittently fed animals had significantly lower blood pressure than the normal fed animals. Using fecal transplant experiments, the researchers then established that the microbiomes of the fasting rats appeared to be directly responsible for the improvements in blood pressure.
“It was particularly interesting to see that the germ-free rats that received the microbiota from the fasting SHRSP rats had significantly lower blood pressure than the rats that received the microbiota from the SHRSP control rats,” says David Durgan, one. researchers working on the study. “These results demonstrated that the microbiota alterations induced by fasting were sufficient to mediate the hypotensive effect of intermittent fasting.”
So what exactly is going on here? Thorough analysis of the microbiota of fasting animals revealed higher levels of bile acids than hypertensive animals on a normal diet.
âWe applied shotgun sequence analysis of the entire microbiota genome as well as non-targeted metabolomic analysis of plasma and gastrointestinal luminal content,â says Durgan. In support of this finding, we found that supplementing animals with cholic acid, a primary bile acid, also significantly reduced blood pressure in the SHRSP model of hypertension. “
Taken together, these new studies provide a better understanding of how the gut microbiome helps catalyze beneficial metabolic outcomes of dietary interventions. There is still a lot of work to be done to understand whether frequent intermittent fasting cycles might improve hypertension during the DASH diet, but in the short term it appears that a short period of fasting before a dietary change may help reshape the body. microbiome in a beneficial way.
The DASH study was published in the journal Nature communications.
The animal study was published in the journal Traffic research.