The Effects of Mixed Nut Consumption on the Microbiome in Healthy Adults

Abstract

Objectives Nut consumption has been shown to have a wide range of health benefits from lowering cholesterol to extending longevity. Due to their prebiotic content, one potential mechanism is that nuts favorably impact the symbiotic relationship of the gut microbiome. So far studies have investigated the role of individual types of nuts, but more research is needed to determine if favorable microbiota changes extend to a nut mixture, which is often how people consume nuts. The purpose of this study was to examine the effects of daily mixed nut consumption on microbiome diversity as it relates to human health. Methods Subjects (N = 20) were randomized into two groups either consuming 42g (250 Kcal) of mixed nuts (n = 10, 9 females, 1 male, age 24.5 ± 1.2 y, BMI 24.8 ± 1.5 kg/m2) containing cashews, almonds, pecans, peanuts, walnuts, pistachios, Brazil and macadamia nuts or 46g of iso-caloric lightly salted potato chips (n = 10, 8 females, 2 males, age 24.2 ± 1.0 y, BMI 23.3 ± 1.0 kg/m2) every day for three weeks. Stool samples were collected at baseline and week three in DNA/RNA shield solution and isolated DNA was sequenced using 16S rRNA gene sequencing. Microbiome data were analyzed for alpha and beta diversity and taxa abundance using R. Results The intervention did not lead to significant changes in microbiota composition at the phyla or genera level; however, a trend towards a decreased Bacteroidetes to Firmicutes ratio was observed after consumption of potato chips for three weeks while an opposite trend was observed following mixed nut consumption. For within-subject (alpha) and between-subject (beta) diversity there were no significant changes at the species level. A significant (P = 0.018) 11.9 log fold increase in Dialister invisus was observed in the potato chips group. Although not statistically significant, the mixed nuts group had a 7.1 log fold decrease in Prevotella bivia (P = 0.058), a 4.5 log fold decrease in Eubacterium dolichum and a 3.6 log fold increase in Bifidobacterium longum. Conclusions Results indicate that the consumption of mixed nuts did not lead to a significant shift in microbiota composition; however, trends at the phyla and species levels suggest a longer intervention may be needed to observe microbiota changes that may contribute to human health. Funding Sources American Heart Association (16GRNT31360007).