A number of studies have documented the health benefits of walnuts. One of the latest comes from Penn State, where researchers showed that eating two to three ounces of walnuts daily as part of a healthy diet can improve gut health and reduce the risk of heart disease. Earlier studies had shown that eating whole walnuts daily can lower cholesterol levels and blood pressure, perhaps due to beneficial changes in the gut microbiome.
The Penn State study included 42 men and women between the ages of 30 and 65 who were overweight or obese. Initially, they followed an average American diet for two weeks. Then they were randomly assigned to one of three diets, one of which included whole walnuts. Another provided the same amount of alpha-linolenic acid and polyunsaturated fatty acids found in walnuts, but from other sources, and a third partially substituted oleic acid for the amount of ALA found in walnuts. In all three diets, walnuts or vegetable oils replaced saturated fat. All the participants followed each diet for six weeks with a break between diet periods. To analyze the bacteria in the gastrointestinal tract, the researchers collected fecal samples from the participants 72 hours before each one finished the initial diet and again 72 hours before finishing each of the three study diet periods
The researchers reported that the walnut diet increased the numbers of gut bacteria that have been associated with health benefits. One, Roseburia, has been linked to protection of the gut lining. Changes in other types of bacteria were favorably associated with reductions in blood pressure, total cholesterol and non-HDL cholesterol.
“The findings add to what we know about the health benefits of walnuts, this time moving toward their effects on gut health,” said Penny Kris-Etherton, Ph.D., distinguished professor of nutrition. She added that the new findings “give 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.”
An investigation from the Harvard T.H. Chan School of Public Health published in 2017 found that eating several small servings of nuts per week may significantly lower your risk of heart attack or stroke. Here, researchers analyzed up to 32 years’ worth of data from more than 210,000 health professionals. Results showed that compared with people who never or almost never ate nuts, those who consumed one ounce of nuts five or more times per week had a 14 percent lower risk of cardiovascular disease and a 20 percent lower risk of coronary heart disease during the study period. Both walnuts and peanuts (but not peanut butter) were linked with the lower risk.
Walnuts are definitely good for you, as long as you don’t overdo it; like other nuts, they are relatively high in calories. I like raw, unsalted walnuts and try to eat a few every day.
Andrew Weil, M.D.
Alyssa M Tindall et al. “Walnuts and Vegetable Oils Containing Oleic Acid Differentially Affect the Gut Microbiota and Associations with Cardiovascular Risk Factors: Follow-up of a Randomized, Controlled, Feeding Trial in Adults at Risk for Cardiovascular Disease.” The Journal of Nutrition, December 18, 2019, DOI: 10.1093/jn/nxz289