Dietary Bioactive Components
To examine gut bacterial composition following a higher-saturated fatty acids (SFA) run-in, standard Western diet (SWD) and 3 study diets where SFA was replaced with: whole walnuts (WD); vegetable oils in a fatty acid matched diet devoid of walnuts (WFMD); vegetable oils in an oleic acid replaces α-linolenic acid (ALA) diet (ORAD) and devoid of walnuts. Correlations between the bacterial composition and cardiovascular disease (CVD) risk factors were also explored.
Adults at CVD risk (n=42) were included in this secondary analysis of a randomized, crossover, controlled-feeding study that reported improvements in CVD risk factors. Only significantly changed risk factors were correlated with significantly enriched bacteria. Fecal collections followed a 2-week run-in diet and three 6-week diet periods. Linear discriminant analysis Effect Size plots were used to determine enriched taxa.
Results : Following the WD, Roseburia (mean relative abundance=4.2%, LDA=4, P=0.0008), Eubacterium eligensgroup (1.4%, 4, 0.05), Lachnospiraceae UCG001 (1.2%, 3, 0.03), Lachnospiraceae UCG004 (1.0%, 3, 0.04) and Leuconostocaceae (0.03%, 3, 0.05) were abundant relative to the SWD. Relative to the SWD, Roseburia (mean relative abundance=3.6%, LDA=4, P=0.02) and Eubacterium eligensgroup (1.5%, 3, 0.02) were enriched following the WFMD, and following the ORAD Clostridialesvadin BB60 (0.3%, 2, 0.04) was most abundant. Significant associations existed between enriched bacteria following the WD and CVD risk factors. Eubacterium eligens correlated with brachial (R=-0.5, P=0.0009) and central mean arterial pressure (MAP; -0.5, 0.002), and central diastolic blood pressure (cDBP; -0.5, 0.0006). Lachnospiraceae correlated with brachial (R=-0.4, P=0.02) and central MAP (-0.4, 0.02), cDBP (-0.3, 0.04), total cholesterol (TC; -0.4, 0.03), and non-HDL-C (-0.4, 0.02). Leuconostocaceae correlated with brachial (R=0.3, P=0.03) and central MAP (0.3, 0.03).
Similar eubiotic bacteria were enriched by the WD and WFMD suggesting ALA and linoleic acid affect the gut microbiome. Enrichment of Lachnospiraceae and associations with improved CVD risk factors suggests the microbiome contributes to the beneficial health effects of walnuts.
Funding Sources : The California Walnut Commission and National Center for Advancing Translational Sciences, NIH.