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Caviar for the intestinal flora

Several studies have already proven the positive health effects of walnuts, including reducing risk factors for heart disease and colon cancer. According to a new study, the underlying mechanism may be explained by how nuts nourish and affect the microbiota.

The high fiber content of nuts

Nuts contain a significant amount of fiber, as do fruits, vegetables and legumes. Fiber is a good food source for the gut microbiota. They help bacteria break down complex foods and provide them with nutrients. They thus promote the diversity of the microbiota, which has a positive effect on health.

42g of nuts per day

The University of Illinois demonstrated the effects of nut consumption on gut flora and secondary bile acids in adults. Researchers conducted a randomized study in healthy men and women. The participants followed an isocaloric diet of 0 or 42 g of nuts per day. The researchers collected stool and blood samples before and after the isocaloric diet to analyze microbiota, bile acids and health markers such as LDL cholesterol.

Walnuts help gut-protecting bacteria grow

Participants who ate nuts had higher levels of fecal bacteria, roseburia and clostridium. These three bacteria have the ability to produce butyrate, an essential element for the gut. The study also found a reduction in secondary bile acids during the period that participants consumed nuts compared to the control period. Previous studies had found that these acids were present in high amounts in people with colon cancer. In fact, secondary bile acids can damage cells in the gastrointestinal tract. A reduction in secondary bile acids in the intestine can therefore be beneficial to health. After eating nuts, the concentration of cholesterol and LDL cholesterol appeared to be lower than during controls.

However, the researchers found no significant link between cholesterol and gut microbiota. In short, nut consumption changes the composition of the microbiota in the gastrointestinal system, which could explain the beneficial health effects of nuts.


Holscher HD: Walnut consumption alters gastrointestinal microbiota, microbially derived secondary bile acids, and health markers in healthy adults: A randomized controlled trial. J Nutr. doi: 10.1093/jn/nxy004.

* Presse Santé strives to convey health knowledge in a language accessible to all. In NO CASE can the information given replace the advice of a doctor.

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