may not just be a snack, they may also promote good-for-your-gut bacteria
. New research suggests that these "good" bacteria
could be contributing to the heart-health
benefits of walnuts
Researchers found in a randomized and controlled trial, that eating walnuts
daily as part of a healthy diet was associated with increases in certain bacteria
that can help promote health
. Additionally, those changes in gut bacteria
were associated with improvements in some risk factors for heart disease
Dr Kristina Petersen, Assistant Research Professor at Penn State, said the study that was recently published in the Journal of Nutrition
, suggests walnuts
may be a heart
and gut healthy
Dr Petersen told Thailand Medical
News, "Replacing your usual snack especially if it's an unhealthy snack with walnuts
is a small change you can make to improve your diet. 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
Past research has shown that walnuts,
when combined with a diet low in saturated fats, may have heart-healthy
benefits. For example, previous work demonstrated that eating whole walnuts
daily lowers cholesterol levels and blood pressure.
The team said that other research has found that changes to the bacteria
in the gastrointestinal tract also known as the gut microbiome
may help explain the cardiovascular benefits of walnuts
Dr Penny Kris-Etherton, Distinguished Professor of Nutrition at Penn State added, "There's a lot of work being done on gut health
and how it affects overall health
. 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
consumption were related to improvements in risk factors for heart disease
In the study, the researchers recruited 42 participants with overweight or obesity who were between the ages of 30 and 65. Before the study began, participants were placed on an average American diet for two weeks.
Upon completion of this "run-in" diet, the participants were randomly assigned to one of three study diets, all of which included less saturated fat than the run-in diet. 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 walnut
s, without any walnuts
. In all three diets, walnuts
or vegetable oils replaced saturated fat, and all participants followed each diet for six weeks with a break between diet periods.
To study the bacteria
in the gastrointestinal tract, the researchers collected fecal samples 72 hours before the participants finished the run-in diet and each of the three study diet periods.
Dr Petersen added, "The walnut
diet enriched a number of gut bacteria
that have been associated with health
benefits in the past. One of those is Roseburia, which has been associated with protection of the gut
lining. We also saw enrichment in Eubacteria eligens and Butyricicoccus."
The medical 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.
Also, 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
-disease risk factors after the other two diets.
Dr Regina Lamendella, Associate Professor of Biology at Juniata College, said the findings are an example of how people can feed the gut microbiome
in a positive way.
Dr Lamendella added, "Foods like whole walnuts
provide a diverse array of substrates like fatty acids, fiber and bioactive compounds for our gut microbiomes
to feed on. In turn, this can help generate beneficial metabolites and other products for our bodies."
Dr Kris-Etherton added that future research can continue to investigate how walnuts
affect the microbiome
and other elements of health
Dr Kris-Etherton said, "The findings add to what we know about the health
benefits of walnuts
, this time moving toward their effects on gut healt
h. 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."
Reference: Alyssa M Tindall et al. Replacing Saturated Fats with Unsaturated Fats from Walnuts or Vegetable Oils Lowers Atherogenic Lipoprotein Classes Without Increasing Lipoprotein(a), The Journal of Nutrition (2019). DOI: 10.1093/jn/nxz313