Who Knew? This Surprising Food Boosts Gut Microbes, Protects Your Heart

As many individuals have nut allergies, these results also imply that alternative food supplements, which enhance the internal production of homoarginine, could be beneficial as well.

A team of researchers, led by Kristina S. Petersen from Texas Tech University in Lubbock, discovered that incorporating walnuts into an individual’s diet might modify the gut’s microbial composition — known as the microbiome — in a manner that boosts the body’s production of the amino acid L-homoarginine. A deficiency in homoarginine has been associated with an increased risk of cardiovascular disease.

“Research has shown that walnuts may have heart-healthy benefits like lowering cholesterol levels and blood pressure,” remarks Mansi Chandra, an undergraduate researcher at Juniata College in Huntingdon, Pennsylvania. “This motivated us to look at how walnuts benefited the gut microbiome and whether those effects led to the potential beneficial effects. Our findings represent a new mechanism through which walnuts may lower cardiovascular disease risk.”

They employed a method called metatranscriptomics to examine the gene expression of gut microbes. This recently established technology enables the measurement of gene expression levels and the observation of how these levels change in response to different conditions, such as alterations in diet.

Chandra says that “this is the first study to use metatranscriptomics analysis for studying the impact of walnut consumption on the gut microbiota gene expression.”

“These exploratory analyses contribute to our understanding of walnut-related modulation of gut microbiome, which could be very impactful in learning how gut health impacts our heart health in general.”

The metatranscriptomics analysis utilized samples obtained from a prior controlled-feeding study, in which 35 participants with elevated cardiovascular risk underwent a two-week standard Western diet before being randomly assigned to one of three study diets. Participants followed each diet for six weeks with a break in between.

The study diets comprised one incorporating whole walnuts, one containing the same amount of omega-3 fatty acid alpha-linolenic acid (ALA) and polyunsaturated fatty acids as the walnut diet but without walnuts, and one that partially replaced another fatty acid, oleic acid, for the same quantity of ALA present in walnuts without actually consuming walnuts. These diets were devised to gather information on the impact of walnuts on cardiovascular health due to their bioactive compounds and ALA content, as well as to determine whether walnut-derived ALA is the optimal substitute for dietary saturated fat in comparison to oleic acid.

In the new study, researchers employed metatranscriptomics to assess gene expression and bacteria in the gastrointestinal tract using fecal samples collected just before the participants completed the run-in diet and each of the three study diets.

The analysis identified increased levels of Gordonibacter bacteria in the gut of participants following the walnut diet. This bacterium transforms plant polyphenols, specifically ellagitannins and ellagic acid, into metabolites that can be absorbed by the body. Participants on the walnut diet also exhibited higher levels of expression for several genes implicated in crucial metabolic and biosynthetic pathways, including those that boost the body’s production of the amino acid L-homoarginine.

While further research is required to validate these findings, the study could ultimately contribute to the development of walnut-based dietary interventions.

“Since a lot of people are allergic to nuts,” Chandra adds, “these findings also suggest that other food supplements that boost the endogenous production of homoarginine may also be helpful.”

In the future, the researchers aim to employ metabolomic and proteomic analyses to identify the end products of the genes exhibiting higher levels of expression. This would enable a more comprehensive understanding of the underlying biological mechanisms.

Chandra is set to showcase these new findings at Discover BMB, the American Society for Biochemistry and Molecular Biology’s annual meeting, taking place from March 25th to 28th in Seattle.

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