High-Salt Diet Impacts Health of Gut Microbiome

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Reducing salt intake to a healthier level appears to be beneficial for the gut microbiome and blood pressure, especially in females with untreated hypertension, according to researchers at the Medical College of Georgia at Augusta University.

The gut microbiota are all the bacteria, viruses, protozoa, and fungi populating the gastrointestinal tract, having a wide range of functions from helping digest food, immune response, and influencing a predisposition to gain weight. In addition, problems with the microbiome are associated with a wide range of diseases from cancer to gastrointestinal problems to allergies, according to the study authors.

A study was conducted using the blood of 145 adults with untreated hypertension, which found that females who consumed 6 weeks of daily sodium intake close to 2300 milligrams resulted in increased levels of short-chain fatty acids. Half of the participants received either a sodium tablet or placebo tablet 9 times daily for 6 weeks, then switching groups.

The results showed that sodium reduction increased in all 8 of the short-chain fatty acids (SCFAs), with the end product of the fermentation of fibers consumed by our microbiota. These increased levels of SCFAs were consistent with lower blood pressure and increased blood vessel flexibility, according to the study authors.

Higher salt intake drove up blood pressure in both males and females, and improvements were noted in both sexes; however, the shifts were most dramatic for females, according to the researchers. Although microbiota are distinctive through diet and environment, there can be differences between males and females.

“Sodium is a factor in both sexes, but the impact in relationship to the gut microbiome seems more in females,” said Haidong Zhu, molecular geneticist at the Georgia Prevention Institute at the Medical College of Georgia at Augusta University, in a press release. “We need to study it further to see if that is true and why it’s true if it holds. It may be that high-salt affects blood pressure through different pathways in males and females.”

According to the authors, this study is the first to look at how decreasing salt intake in humans affects circulating SCFAs. Additional evidence suggests that a high-salt diet alters the gut microbiome, but there are still little human data.

SCFAs are known to play a role in blood pressure regulation, helping to regulate the release of renin, an enzyme that works to keep the kidneys well perfused and a major player in blood pressure control. Blood levels of SCFAs can be considered an indicator of the health of the gut microbiome, according to the study authors.

The researchers plan to conduct a larger study in the future that also examines fecal samples to more directly assess microbiome content and health and to see whether the sex differences they found are consistent.

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