New Research Shows Walnuts May Be Good for Gut, Heart Health


Walnuts may promote “good-for-your-gut” bacteria, according to new research findings.

Researchers at Penn State found that eating walnuts daily as a part of a healthy diet was associated with increases in certain bacteria that can help promote health. In addition, the changes in gut bacteria were associated with improvements in some risk factors for heart disease.

Previous research in this area has shown that combining walnuts with a diet low in saturated fats may have heart-healthy benefits. Other research has found that changes to the bacteria in the gastrointestinal tract may help explain the cardiovascular benefits of walnuts, according to the researchers.

The randomized, controlled trial included 42 participants with overweight or obesity between the ages of 30 and 65 years. Before the study began, participants were placed on an average American diet for 2 weeks.

Following the diet, participants were randomly assigned to 1 of 3 study diets, all of which included less saturated fat than the “run-in” diet.

The 3 diets included: 1 that incorporated whole walnuts, 1 that included the same amount of alpha-linolenic acid (ALA) and polyunsaturated fatty acids without walnuts, and 1 that partially substituted oleic acid for the same amount of ALA found in walnuts, without any walnuts.

Walnuts or vegetable oils replaced saturated fat in all 3 diets, and all participants followed each diet for 6 weeks with a break in between diet periods.

In order to analyze the bacteria in the gastrointestinal tract, the researchers collected fecal samples 72 hours before participants finished the run-in diet and each of the 3 study diet periods.

After the walnut diet, researchers found that there were significant associations between changes in gut bacteria and risk factors for heart disease.Eubacterium eligenswas inversely associated with changes in several different measures of blood pressure, suggesting that greater numbers ofEubacterium eligenswas associated with greater reductions in those risk factors.

In addition, greater numbers oflachnospiraceaewere associated with greater reductions in blood pressure, total cholesterol, and non-HDL cholesterol. There were no significant correlations between enriched bacteria and heart-disease risk factors after the other 2 diets.

Penny Kris-Etherton, professor of nutrition at Penn State, suggested that future studies can help researchers investigate how walnuts affect the microbiome and other elements of health.


Walnuts may be good for the gut and help promote heart health [news release]. University Park, PA; Penn State: January 16, 2020. Accessed January 30, 2020.

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