Researchers at Penn State have found that consuming walnuts on a daily basis as part of a healthy diet was linked to increases in certain bacteria that can help promote health. Those changes in the gut bacteria were also linked with improvements in some risk factors for diseases of the heart.
Walnuts are not only a tasty snack, but with the new research it appears walnuts contribute “good” bacteria and this may be what provides their heart health benefits. Prior research has found that changes in the gut microbiome may help explain the cardiovascular benefits. And when combined with a diet low in saturated fats, walnuts can also help lower cholesterol levels and blood pressure.
For the study, 42 participants were recruited who had obesity or overweight issues and were between the ages of 30 and 65. Prior to the start of the study, the participants were placed on an average American diet for two weeks.
Following the initial 2 week diet, participants were randomly assigned to one of three study diets. All the diets included less saturated fat than was in the 2 week diet. The diets included one that included whole walnuts, one that included the same amount of ALA (alpha linolenic acid) and polyunsaturated fatty acids without walnuts, and one that partially substituted oleic acid or another fatty acid for the same amount of ALA found in walnuts but without any walnuts.
In all of the three diets, walnuts or vegetable oils replaced saturated fats and all the participants followed each diet for a six week period with a break between diet periods.
In order to analyze the bacteria in the gastrointestinal tract, the team collected fecal samples 72 hours prior to the initial 2 week diet and prior to each of the three study diet periods.
The walnut diet was shown to enrich a number of gut bacteria that have been linked to health benefits in the past. One of the gut bacteria known as Roseburia has been associated with protection for the lining of the gut. The team also saw enrichment in Butyricicoccus and Eubacteria eligens.
The team also discovered that following the walnut diet there were significant links between changes in the gut bacteria and risk factors for heart disease. Eubacterium elegens was inversely linked with changes in several different measures of blood pressure. This suggests that larger numbers of this bacteria was linked with greater reductions in those risk factors.
Greater numbers of Lachnospiraceae were also associated with greater reductions in total cholesterol, blood pressure and non HDL cholesterol. There were no significant associations between enriched bacteria and risk factors for heart disease following the other two diets.
Foods like whole walnuts provide a diverse variety of substrates like fiber, bioactive compounds and fatty acids for our gut microbiomes to feed on. This in turn can help generate beneficial metabolites and a variety of other products for the human body.
The recent findings add to what is already known about the health benefits of walnuts with this new evidence showing their positive affect on gut health. Future research will continue to investigate how walnuts affect the microbiome and other health benefits such as how they might affect blood sugar levels.
To view the original scientific study click below
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