Walnuts may improve gut, heart health: Study

Consumption of walnuts may improve the growth of beneficial gut bacteria, and are associated with improvements in some risk factors for heart disease, according to a new study which may lead to new dietary recommendations for better cardiac health.

The study, published in the Journal of Nutrition, said walnuts may be a heart- and gut-healthy snack. "Substantial evidence shows that small improvements in diet greatly benefit health. Eating two to three ounces of walnuts a day as part of a healthy diet could be a good way to improve gut health and reduce the risk of heart disease," said Kristina Petersen, study co-author from the Pennsylvania State University in the US. Earlier studies had revealed that when combined with a diet low in saturated fats, walnuts may have heart-healthy benefits.

"Replacing your usual snack - especially if it's an unhealthy snack -- with walnuts is a small change you can make to improve your diet," Petersen explained. According to Petersen and her team, changes to the bacteria in the gastrointestinal tract - also known as the gut microbiome - may explain the cardiovascular benefits of walnuts. For the current study, the scientists recruited 42 participants between the ages of 30 and 65, who were either overweight or obese.

The participants were placed on an average American diet for two weeks before the study began. They were then randomly assigned to one of three study diets - all of which included less saturated fat than the pre-study diet. One of the three diets incorporated whole walnuts, and another included natural chemicals present in walnuts - alpha-linolenic acid (ALA) and polyunsaturated fatty acids.

The third diet had partially substituted oleic acid (another fatty acid) for the same amount of ALA found in walnuts. In all the diets, walnuts or vegetable oils replaced saturated fat, the scientists said. The participants followed each diet for six weeks with a break between diet periods, the study noted.