The human gut microbiota plays a crucial role in maintaining host health, with diet being a key modulator of its composition. While the effects of various dietary components on gut microbiota have been extensively studied, the impact of nut consumption remains relatively unexplored. This study aimed to investigate the effect of nut consumption on the human the large intestinal microbiota. Faecal samples from 15 donors were analysed before and after a three-week dietary intervention involving daily consumption of a nut mix containing almonds, macadamias and pistachios (totalling 30g). Faecal characteristics, microbiota composition and fermentation end-products were assessed.
Baseline analysis revealed considerable inter-individual variation in faecal characteristics and microbiota composition. Notably, Bacteroides and Prevotella predominated, reflecting established enterotypes. Microscopic examination post-nut consumption detected nut particles in faeces, indicating incomplete lipid digestion. Increased faecal lipid content post-nut consumption was noted to be significant (p<0.05), with no significant changes observed for the other faecal characteristics.
Alpha diversity analysis indicated no significant alterations in microbial diversity post-nut consumption. However, while no significant differences were observed in short-chain fatty acids and ammonia levels, microbial community structure varied greatly among individuals, suggesting a strong influence of individual factors. Specifically, beta diversity analysis revealed individual-specific microbiota profiles, with no distinct changes attributable to nut consumption. Yet core microbiome analysis identified genera associated with nut consumption or abstinence, suggesting subtle microbial community shifts.
Predictive metabolic pathway profiling indicated an increase in fatty acid β-oxidation pathways post- nut consumption, suggesting microbial involvement in lipid degradation. This finding was in alignment with the significant differences (p<0.05) in faecal lipid content post-nut consumption noted. Despite individual variation, stable equilibrium states of the microbiota were evident, suggesting longer-term dietary interventions may induce pronounced changes to the large intestinal microbiota.
Overall, this study provides insights into nut-induced alterations in faecal lipid content and microbiota composition. The presence of undigested lipids in faeces is indicative of potential health benefits associated with nut consumption. Future studies with longer intervention periods and larger nut intake are warranted to further elucidate the effects of nut consumption on the large intestinal microbiota.