New studies have found that rats trained to become hypertensive on a high-salt diet appeared to greatly benefit from a plant-based diet. When rats get pregnant, the whole grain diet protects both the mothers and their pups against preeclampsia, which can be fatal.
Despite the fact that we’ve all been told to stay away from the salt shaker, an estimated 30-50 percent of us experience a substantial increase in blood pressure as a result of excessive salt consumption, with the percentages being significantly higher and more severe in the African-American population.
Researchers from the Medical College of Georgia and the Medical College of Wisconsin report in the journals ACTA PHYSIOLOGICA and Pregnancy Hypertension: An International Journal of Women’s Cardiovascular Health, that the gut microbiota, which contains trillions of microorganisms that help us digest food and play a key role in regulating our immune system’s response, is also a player in the unhealthy response to salt.
According to Dr. David L. Mattson, chair of the MCG Department of Physiology, Georgia Research Alliance Eminent Scholar in Hypertension, and senior author on the two studies, the findings provide more evidence of the “potential power” of nutritional intervention to improve the gut microbiota and, as a result, our long-term health.
They are the outcome of the surprising discovery that the protection works even in the Dahl salt sensitive rat, a well-established model of salt-sensitive hypertension.
These rats are bred to develop hypertension and progressive renal damage when fed a high-salt diet, as their name suggests. Charles Rivers Laboratories received a colony of Dahl SS rats fed a milk-based protein diet from the Medical College of Wisconsin in 2001. The rats were shifted to a grain-based diet after they arrived at Charles River Laboratories in Wilmington, Massachusetts. Both diets are low in sodium, while the protein-based, or casein-based, diet has less.
The relocated rats had considerably less high blood pressure and associated kidney damage than the rat colonies that remained in Wisconsin when high-salt content was introduced to their diet.
“People ordered them and used them with the idea that they were going to study hypertension and they developed next to none,” Mattson says. Mattson and his colleagues at MCG and MCW write that more than a decade of study has documented these variances and has now proved that developing salt-sensitive hypertension isn’t only about sodium consumption.
“The animal protein amplified the effects of the salt,” says Mattson, a longtime hypertension researcher, who along with Dr. Justine M. Abais-Battad, physiologist, and postdoc Dr. John Henry Dasinger, came to MCG from Wisconsin two summers ago.
“Since the gut microbiota has been implicated in chronic diseases like hypertension, we hypothesized that dietary alterations shift the microbiota to mediate the development of salt-sensitive hypertension and renal disease,” they write in the journal ACTA PHYSIOLOGICA.
According to lead author Abais-Battad, the gut microbiome is meant to metabolize what we consume, break it down, and put it in a form that offers us nutrients, and it also reflects what we consume. When they looked at the microbiomes in the rats: “Sure enough, they were different,” she says. They analysed both rat colonies’ genetic material and discovered they were “virtually identical,” yet their responses to a high-salt diet were not, according to Mattson.
The Wisconsin rats had kidney damage and inflammation, both markers of high blood pressure, as expected, while the Charles River rats on the same high-salt diet had much less of these negative outcomes. The substantial variances in their microbiome mirrored the disparities in illness incidence and severity.
When they gave the protected rats some of the Wisconsin rats’ distinctive gut microbiota via fecal transplant, the rats experienced an increase in blood pressure, kidney damage, and the number of immune cells moving into the kidneys, organs that regulate fluid balance, in part by determining how much sodium is retained. It also changed the composition of their microbiota.
The authors believe that when they shared the microbiota of the protected rats with the Wisconsin rats, it had no effect, possibly because the new microbes couldn’t thrive in the face of the animal-based protein diet.
Preeclampsia is a potentially fatal condition that occurs during pregnancy when the mother’s blood pressure rises over normal levels and organs such as the kidneys and liver show indications of damage. Dahl salt sensitive rats have been shown to develop preeclampsia even when on a low-salt diet.
The Dahl SS rats were kept on their respective plant- or animal-based protein diets, which are both quite low in salt, and both groups had three different pregnancies and births to examine the influence of diet in this situation.
According to Dasinger, the study’s first author, rats on the whole wheat-based chow were protected against preeclampsia, but nearly half of the rats on the animal-based casein diet experienced this serious pregnancy problem.
They had a significant increase in protein spilled into their urine, a sign of kidney trouble that got worse with each pregnancy; increased inflammation, a driver of high blood pressure; increased pressure inside the renal artery; and significant signs of kidney destruction when the organs were examined again. Stroke, renal illness, and other cardiovascular problems were among the ailments that claimed their lives.
“This means that if mom is careful with what she eats during pregnancy, it will help during the pregnancy, but also with her long-term health and could provide protective effects for her children,” Dasinger says. The researchers point out that this supports the message that physicians and scientists have been giving to expectant moms for decades.
According to Dasinger, they aim to study more closely at the influence of nutrition on children and if protection is passed on to kids through breast milk. They want to look at the function of the immune cells that show up because they know that food affects immune cell activity. They already have some evidence that T cells, which drive the immunological response, are a part in the development of preeclampsia.
According to the research done by Abais-Battad, Dasinger, and Mattson, a fundamental difference between the various diets is that the protein-based diet produces more proinflammatory chemicals, whilst the plant-based diet appears to decrease these factors.
They’re also looking at how nutrition affects the renin-angiotensin system, which helps control blood pressure. They also want to learn more about the bacteria that raise blood pressure and the substances they create.
High blood pressure is the most modifiable risk factor for cardiovascular disease, and nearly half of us are hypertensive, according to the latest guidelines from organizations like the American Heart Association, which say a systolic, or top number of 120+ is elevated and top numbers of 130-139 is stage one hypertension. According to the researchers, nutrition, particularly a high-salt diet, is one of the most modifiable risk factors for high blood pressure and cardiovascular disease. The gut microbiota of hypertensive humans and animals has been reported to be imbalanced and less varied than that of those with normal blood pressure.