In the news: Nuts Linked to Kidney Health Polyphenols Help Gut Bacteria Thrive?

Eating Nuts Tied to Better Kidney Health

In chronic kidney disease (CKD), the kidneys become impaired over time and less able to cleanse the blood of toxic waste and extra fluid. This in turn may lead to other problems including high blood pressure, heart disease and stroke. CKD is relatively common in the U.S. with more than 1 in 7, that is 15% of adults or 37 million people, estimated to have the condition according to the Centers for Disease Control.

In recently published research(1) investigators wanted to assess whether consuming nuts might be protective against CKD, lowering the risk for developing it. Previous studies suggest that including nuts in the diet may have benefit in cardiovascular disease (CVD), obesity, cancers, and nonalcoholic fatty liver disease. Nuts may work by reducing oxidative stress and inflammation, improving blood vessels’ ability to dilate, and supporting healthy blood lipid levels.

The researchers used data from over 6,000 U.S. adults (aged 20 years or older) to evaluate the association between the consumption of nuts and the frequency of CKD in the population, as well as the mortality associated with CKD

Consuming nuts one to six times per week was linked to a lower frequency of CKD, with 33% lower odds of having CKD.

There was also an association between eating nuts one to six times weekly and lower death rate from any cause and death from CVD in people who did not have chronic kidney disease. For those with CKD, higher nut intake was also tied to lower death from any cause.

Eating nuts once to six times weekly may help lower the risk of developing CKD, though more research is needed to confirm the study’s observations.

For those who already have chronic kidney disease, it is always best to check with your physician for specific dietary advice. Diet is often a key part of managing CKD, with the purpose of slowing progression to kidney failure.

While there’s no consensus on foods that are specifically recommended, the general idea is to get adequate calories while lowering the intake of proteins, phosphorus, sodium, potassium, and organic acids. Since nuts contain phosphorus and potassium, consuming larger amounts of certain nuts may not be appropriate for everyone depending on their stage of kidney disease.

Dietary Polyphenols May Help Prevent Inflammation in Elderly Via Gut Microbiota

Researchers from the University of Barcelona have shown that a diet high in polyphenols can support micro-organisms that produce compounds important to our health. In this case, the polyphenol-rich diet raised levels of a compound called indole 3-proprionic acid or IPA.

IPA is generated by intestinal bacteria when the bacteria metabolize an amino acid (tryptophan) in foods. IPA has shown anti-inflammatory and antioxidant effects, and it helps keep the intestinal wall intact and functioning well.

In the study(2), participants over 60 years of age were randomly assigned to a high polyphenol or control diet, then switched over to the other diet over an eight-week period. The high polyphenol diet included foods rich in polyphenols like green tea, dark chocolate, and fruits such as apples, pomegranate, and blueberries.

During the high-polyphenol intake period, the participants had higher blood levels of IPA, a decrease in biomarkers of inflammation, and an increase in the diversity of bacteria associated with a healthy gut. Interestingly, the same beneficial effects were not seen in participants with kidney disease. According to the authors, this may be due to the altered composition of their microbiota compared to those with normal kidney function.

References

1. Wang K, et al. Nut consumption and effects on chronic kidney disease and mortality in the United States. Am J Nephrology. 53:503–512, 2022.
2. Peron G, et al. A polyphenol-rich diet increases the gut microbiota metabolite indole 3-propionic acid in older adults with preserved kidney function. Mol Nutr Food Res. 2100349, 2022.