Walnuts may be more than just a tasty snack. Researchers from the University of Pennsylvania have found that they may also promote healthy gut bacteria, which may lead to a healthier heart.
For their study, the researchers recruited 42 people who were either overwieght or obese aged between 30 and 65. Prior to the research, they were each placed on an average American diet for two weeks. After this preparatory diet, they were then randomly assigned to one of three study diets. One included whole walnuts; another the same amount of alpha-linolenic acid (ALA) and polyunsaturated fatty acids only without walnuts, and one that partially substituted oleic acid for the same amount of ALA present in walnuts, again without the nut.
In each diet, saturated fat was replaced by either walnuts of vegetable oils, with each participant following their meal plans for six weeks. To analyze differences in gut bacteria among the participants, the researchers examined fecal samples from each 72 hours prior finishing their preparatory diets and 72 hours prior to the end of each of the three study diets too.
In particular, they found that the walnut diet enriched gut bacteria previously linked to health benefits. For example, they found higher quantities of Roseburia, previously associated with the protection of the gut lining, in the feces of those on the walnut diet.
More than this, the researchers found that those on the walnut diet also saw increases in gut bacteria associated with a reduced risk factor for heart disease. For example, they noticed elevated levels of eubacterium eligens, bacteria inversely correlated with changes in several measures of blood pressure.
Adding to this, they also found that those on the walnut diets had greater quantities of Lachnospiraceae in their microbiomes, associated with reduced blood pressure, total cholesterol and non high density lipoprotein (HDL) cholesterol. Meanwhile, the researchers noted that the walnut-free diets had no significant correlation between enriched bacteria and risk factors for heart disease.
According to Penny Kris-Etherton, a nutrition professor from the University of Pennsylvania, “The findings add to what we know about the health benefits of walnuts, this time moving toward their effects on gut health...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."