Two new studies examining the link between fasting and the microbiome offer new insights into how our gut bacterial makeup can be reshaped by short-term dietary changes and how this can benefit cardiovascular health. Research suggests that not only is fasting beneficial for reshaping the microbiome, but also fasting briefly before starting a new diet can enhance the diet’s beneficial effects.
A number of previous studies have shown that the bacteria community living in our gut plays an important role in influencing our overall health through the foods we eat. For example, two studies from last year highlighted the significant relationships between diet, gut microbiome composition and healthy aging.
Fasting before the DASH diet
Newly published research now offers more detailed insights into these relationships and examines how dietary interventions, particularly fasting, can catalyze improvements in blood pressure through changes in the microbiome. The first study, published in the journal Nature Communications, showed how short-term fasting resulted in acute improvement in blood pressure when a longer-term Mediterranean diet was followed.
One of the first treatments often offered to patients with high blood pressure is a dietary intervention known as DASH (Dietary Approach to Stop Hypertension). The DASH diet is an effective initial treatment for high blood pressure, but it is still unclear how it directly improves blood pressure. It is believed that dietary changes in the microbiome could cause the improvements.
To test this hypothesis, a research team recruited 71 subjects with high blood pressure. The cohort was randomly divided into two groups, each tasked with following the DASH diet for three months. One group was also instructed to fast for five days prior to the DASH diet.
Researchers tracked changes in the immune biomarker and microbiome, and discovered greater blood pressure improvements in the cohort that were accompanied by long fasts prior to their diet change. Interestingly, the immune and microbiome changes observed in the fasting cohort were markedly different from those seen in volunteers only after the DASH diet.
The researchers believe that the fasted diet quickly changes the composition of the microbiome and increases the availability of short-chain fatty acids. This short-term change could later change the body’s response to the DASH diet.
“The body mass index, blood pressure and the need for antihypertensive drugs remained lower in the long term in volunteers who started a healthy diet with a five-day fast,” notes Dominik Müller, one of the researchers involved in the project.
The microbiome connection
Another newly published study conducted by researchers at Baylor College of Medicine sought to better understand how gut microbes can affect blood pressure. Researchers were also interested in whether this result could be achieved without fasting, either through a dietary supplement or through direct manipulation of microbiome composition.
The researchers conducted a series of studies using a specific animal model developed to study high blood pressure known as SHRSP rats (spontaneous hypertensive stroke). The first test was whether changes in the microbiome caused by fasting resulted in an improvement in blood pressure.
For nine weeks, a group of SHRSP rats was fed only on alternate days. At the end of this period, the intermittently fed animals showed significantly lower blood pressure compared to the animals that ate normally. Using fecal transplant experiments, the researchers then found that the fasting rats’ microbiomes appeared to be directly responsible for the improvements in blood pressure.
“It was particularly interesting to see that the aseptic rats that received microbiota from the fasted SHRSP rats had significantly reduced blood pressure than the rats that received microbiota from SHRSP control rats,” says David Durgan, one of the researchers. who worked on it the studies. “These results indicated that the microbiota changes induced by fasting were sufficient to mediate the hypotensive effects of interrupting the fast.”
What exactly is going on here? A detailed analysis of the microbiota of the fasting animals revealed higher bile acid levels than the hypertensive animals that ate normally.
“We performed shotgun sequence analysis of the entire genome of the microbiota, as well as non-targeted metabolomics analysis of plasma and gastrointestinal lumen content,” explains Durgan. We found that supplementing animals with cholic acid, a primary bile acid, also significantly lowered blood pressure in the SHRSP model for hypertension. “
Taken together, these new studies provide better insights into how the gut microbiome helps catalyze beneficial metabolic outcomes from dietary interventions. Much work remains to be done to understand whether frequent intermittent fasting cycles can improve high blood pressure while on the DASH diet. In the short term, however, it seems that briefly fasting before changing your diet can help reshape the microbiome to advantage.
The DASH study was published in the journal Nature Communications.
The animal study was published in the journal Circulation Research.
Source: Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Baylor College of Medicine