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January 17, 2020

Snacking on walnuts improves gut and heart health, Penn State study finds

Healthy Eating Nutrition
Walnuts Penn State Source/

Eating two to three ounces of walnuts a day improves gut health and reduces the risk of heart disease, Penn State University researchers say.

A steady dose of walnuts as part of a healthy diet could have significant benefits for your gut and your heart, according to research out of Penn State University.

Previous research out of Penn State has shown that walnuts have a tendency to curb cravings for unhealthy foods, but the latest study shows the nutritional and cardiovascular benefits walnuts offer for those at risk of heart disease.

“There’s a lot of work being done on gut health and how it affects overall health,” said Penny Kris-Etherton, a professor of nutrition at Penn State. “So, in addition to looking at factors like lipids and lipoproteins, we wanted to look at gut health. We also wanted to see if changes in gut health with walnut consumption were related to improvements in risk factors for heart disease.”

The current study selected 42 overweight and obese participants between 30 and 65 years old. They were placed on an average American diet for two weeks prior to the start of the study.

Once the study began, the participants were randomly assigned to follow one of three diets, each involving a reduction in saturated fat.

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

All participants followed each of the diets for six weeks, with a small break between each diet period. To examine changes in gut bacteria, scientists collected fecal samples from each participant during the pre-study period and during their trial with each diet.

“The walnut diet enriched a number of gut bacteria that have been associated with health benefits in the past,” said Kristina Petersen, an assistant research professor at Penn State. “One of those is Roseburia, which has been associated with protection of the gut lining. We also saw enrichment in Eubacteria eligens and Butyricicoccus.”

Researchers suggest eating two to three ounces of walnuts a day to improve gut health and reduce the risk of heart disease.

Eubacteria eligens, specifically, was associated inversely with changes in several measures of blood pressure and accompanying heart disease risks.

“The findings add to what we know about the health benefits of walnuts, this time moving toward their effects on gut health,” added Kris-Etherton. “The study gives us clues that nuts may change gut health, and now we’re interested in expanding that and looking into how it may affect blood sugar levels.”

The study received help from researchers at the Children's Hospital of Philadelphia and Juniata College, with support from the California Walnut Commission and the National Center for Advancing Translational Sciences’ Clinical and Translational Science Award program.

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