Does salt harm the gut microbiome?
According to a recent study, lower salt intake seems to be beneficial for the gut microbiome and blood pressure. So it is recommended to eat less salt. This is especially true for women with untreated high blood pressure, as they experience more of an impact from greater salt intake.
The recent joint study by the Queen Mary University of London and the Medical College of Georgia found that increased salt intake appeared to be detrimental to blood pressure and the gut microbiome. The results of the study were presented in the English-language journal "Hypertension".
Data from 145 people were analyzed
When examining the blood of 145 adult women and men with untreated hypertension, the researchers found that low salt intake can improve the intestinal flora. Women in particular showed an increased content of short-chain fatty acids in the blood after just six weeks of daily sodium intake of around 2.3 grams, an indicator of a healthy microbiome. The German Nutrition Society (DGE) recommends a maximum of six grams of table salt a day.
Does the microbiome regulate blood pressure?
There is growing evidence that the microbiome plays a direct role in regulating blood pressure. New findings suggest that a high-salt diet changes the gut microbiome, especially in animal models for salt-sensitive hypertension. In their current study, the researchers tried to understand the underlying mechanisms of how a high-salt diet causes high blood pressure.
What are the functions of the gut microbiota?
The gut microbiota includes all the bacteria, viruses, protozoa and fungi that populate the gastrointestinal tract. These have a variety of functions, from supporting the digestion of food to the immune response and influencing the tendency to gain weight.
What Are Circulating Short Chain Fatty Acids?
Circulating short-chain fatty acids are an important source of energy for the epithelial cells that line the large intestine and prevent content from escaping from the gastrointestinal tract into the body. Short chain fatty acids are believed to also play a role in protecting against common problems such as inflammation, obesity, and diabetes.
How do circulating short chain fatty acids affect blood pressure?
Circulating short chain fatty acids are already known to play a role in regulating blood pressure. These small intestinal metabolites are absorbed into the entire bloodstream. They bind to receptors in the blood vessels and kidneys, which play an important role in the release of the enzyme renin. Renin ensures good blood flow to the kidneys and plays an important role in blood pressure control. The blood levels of circulating short-chain fatty acids can be seen as an indicator of the health of the gut microbiome, the researchers report.
What were the expectations?
The research group's hypothesis was that even a modest reduction in salt intake would change the levels of circulating short-chain fatty acids and lower blood pressure.
How did the investigation work?
No stool samples were taken from the study participants. Instead, circulating short chain fatty acids were examined. For two weeks, all participants received detailed instructions on how to reduce their sodium intake to around 2,000 milligrams a day. In the randomized, placebo-controlled study, half of the participants received either a sodium or a placebo tablet nine times a day for six weeks. After the period, the groups were changed.
What did lower salt intake do?
The researchers found that reducing sodium intake increased all eight short-chain fatty acids, which are the end product of the fermentation of fibers that are broken down by the microbiota. Humans naturally do not have enzymes to digest many of these fibers.
What did increased levels of circulating short chain fatty acids do?
The team found that increased circulating short-chain fatty acid levels were consistently associated with lower blood pressure and increased blood vessel flexibility. Periods of higher salt intake raised blood pressure in both men and women. Lower salt intake led to an improvement in blood pressure.
Effects on women were stronger
The effects of salt intake were most evident in women, explains the research group. There are generally consistent differences in microbiota between men and women. Sodium is a factor in both sexes, but the effects related to the gut microbiome appear to be more pronounced in women. More research is now needed to check this more closely. It may well be that high salt levels affect blood pressure in men and women in different ways.
Effects on systolic blood pressure
For example, in the 24-hour measurement, systolic blood pressure was almost five points lower when women were on a low-salt diet compared to women who were on a high-salt diet. Systolic blood pressure was only three points lower in men on a low-salt diet compared to men on a high-salt diet.
Future studies should include faecal samples
In the future, a larger study will be carried out in which faecal samples will also be examined in order to assess the microbial content and health more directly. This would make it possible to determine whether the gender differences that emerged in the current study persisted. (as)
Author and source information
This text corresponds to the requirements of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
- Li Chen, Feng J. He, Yanbin Dong, Ying Huang, Changqiong Wang, Gregory A. Harshfield, Haidong Zhu: Modest Sodium Reduction Increases Circulating Short-Chain Fatty Acids in Untreated Hypertensives, in Hypertension (Posted Jun 1, 2020), Hypertension