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Walnuts are not just a tasty snack, they also promote bacteria that are good for your gut. New research suggests that these good bacteria could be contributing to the health benefits of walnuts. 

In a trial, the researchers found that eating walnuts every day as a part of a healthy diet was linked to the increase of certain bacteria that can help promote health. Also, those changes in the gut bacteria were linked to improvements in some risk factors for heart disease. 

The assistant research professor at Penn State, Kristina Petersen, said that the study, published in the Journal of Nutrition, suggests that walnuts may be a snack that is healthy for the heart and the gut. 

Walnut is a healthy snack

Petersen said that replacing your usual snack, especially if it is not healthy, with walnuts is a small change that you can make in order to improve your diet. The main evidence shows that small improvements in diet can greatly benefit our health. Eating at least two to three ounces of walnut a day as part of a healthy diet could be a good way to improve gut health and it can reduce the risk of heart disease. 

Previous research has shown that when walnuts are combined with a diet that is low in saturated fats, it may have heart-healthy benefits. For example, the previous work demonstrated that eating whole walnuts daily can lower cholesterol levels and blood pressure. 

According to the researchers of the study, the previous research has found that changes to the bacteria in the gastrointestinal tract, which is also known as the gut microbiome, can help explain the cardiovascular benefits of eating walnuts. 

Penny Kris-Etherton, a distinguished professor of nutrition at Penn State said that there is a lot of work that is being done on gut health and how it affects overall health. So, in addition to looking at factors like lipoproteins and lipids, they wanted to look at gut health. They also wanted to see if changes in gut health with walnut consumption were related to improvements in risk factors for heart disease. 

For the study, the researchers recruited around 42 people with overweight or obesity issues and who were between the ages of 30 and 65. Before the study began, the participants were placed on an average American diet for two weeks. 

After the American diet, they were randomly assigned to one of the three study diets, all of which included less saturated fat than the run-in diet. The diets of the participants included one that included whole walnuts, one that included the same amount of alpha-linolenic acid or ALA and polyunsaturated fatty acids without walnuts, and one that substituted oleic acid for the same amount of ALA found in walnuts, without adding any walnuts in the diet.  

In all of the three diets, vegetable oils or walnuts replaced saturated fat, and all participants followed each diet for six straight weeks with a break between diet periods. 

Health benefits of walnuts

In order to analyze the bacteria in the gastrointestinal tract, the researchers of the study got fecal samples just 72 hours before the participants finished the American diet and before they finished each of the three study diet periods. 

Petersen said that the walnut diet enriched a number of gut bacteria that have been linked to health benefits in the past. One of those is Roseburia, which has been linked to the protection of the gut lining. They also saw enrichment in Eubacteria eligens and Butyricicoccus

The associate professor of biology at Juniata College, Regina Lamendella, said that the findings are an example of how people can feed the gut microbiome in a positive way. She said that foods like walnuts provide a very diverse array of substrates, like fatty acids, bioactive compounds, and fiber, for our gut microbiomes to feed on. In turn, this can help create beneficial metabolites and other products for our bodies. 

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