This is the nut you should be eating for better gut health according to a new study


Close-up of a variety of dried fruit and nuts on a table
Close-up of a variety of dried fruit and nuts on a table
Researches have uncovered another good reason to add this nut to your daily diet.

Whether it’s a strong immune system, great mental wellbeing or healthy radiant skin, good gut health and a well-balanced gut microbiome is thought to be the answer to keeping many common ailments at bay. While we know that probiotic-rich foods – such as fermented food and yoghurt – can help keep our gut bacteria healthy and happy, scientists have recently discovered that eating walnuts could promote good gut bacteria.

In a study published in the Journal of Nutrition, researchers found that in a randomised, controlled trial, eating walnuts daily, in conjunction with a healthy diet, was associated with an increase in certain health-promoting bacteria. The study also found that the changes in gut bacteria were associated with improvements in some risk factors for heart disease.

“Replacing your usual snack – especially if it’s an unhealthy snack – with walnuts is a small change you can make to improve your diet,” said Kristina Petersen, assistant research professor at Penn State.

“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.”

Previous studies have shown that walnuts, when eaten as part of a diet low in saturated fat, may have heart-health benefits such as helping to lower cholesterol levels and blood pressure. 

The researchers involved in the new study believe that changes to the gut microbiome might help explain the cardiovascular benefits of walnuts. 

“There’s a lot of work being done on gut health and how it affects overall health,” said Penny Kris-Etherton, professor of nutrition at Penn State.

“So, in addition to looking at factors like lipids and lipoproteins, we wanted to look at gut health. We 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, participants we placed on an average American diet for two weeks before being randomly assigned one of three study diets. The diets included one that incorporated whole walnuts, one that included the same amount of alpha-linolenic acid (ALA) and polyunsaturated fatty acids without walnuts, and one that partially substituted oleic acid (another fatty acid) for the same amount of ALA found in walnuts, without any walnuts. The participants were on the diets for six weeks with a break in between.

“The walnut diet enriched a number of gut bacteria that have been associated with health benefits in the past,” Petersen said. “One of those is Roseburia, which has been associated with the protection of the gut lining. We also saw enrichment in Eubacteria eligens and Butyricicoccus.”

The researchers also found that after the walnut diet, there were significant associations between changes in gut bacteria and risk factors for heart disease. Eubacterium eligens was inversely associated with changes in several different measures of blood pressure, suggesting that greater numbers of Eubacterium eligens was associated with greater reductions in those risk factors.

Additionally, greater numbers of Lachnospiraceae were associated with greater reductions in blood pressure, total cholesterol, and non-HDL cholesterol. There were no significant correlations between enriched bacteria and heart-disease risk factors after the other two diets.

“The findings add to what we know about the health benefits of walnuts, this time moving toward their effects on gut health,” Kris-Etherton said. “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.”

Discover our other favourite foods for great gut health right here. 


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