Active vitamin D linked to better gut health in elderly men

Men who have higher serum concentration of the active form of vitamin D (1,25[OH]₂D) tend to have gut flora enriched in butyrate-producing bacteria, a recent study has found. In turn, this microbiota structure may promote better gut health.

A total of 567 older men (mean age, 84.2±4.1 years) participated in a cross-sectional analysis. Serum levels of vitamin D metabolites (25-hydroxyvitamin D [25(OH)D], 1,25[OH]₂D, and 24,25[OH]₂D) and were measured using liquid chromatography with tandem mass spectrometry. Microbiome analysis was performed on stool samples that were subjected to 16S ribosomal RNA sequencing and taxonomic assignments.

Most (74.8 percent) of the men were taking some form of vitamin D supplementation, while only 7.2 percent were deficient. Those who were recruited from the site with the highest annual sun exposure had the highest 25(OH)D levels, but were not significantly advantaged in terms of 1,25(OH)₂D, suggesting that sunlight strongly affected vitamin D stores, but not its active form.

Random forest analysis found six sub-operational taxonomic units (sOTUs) that were statistically correlated with vitamin D concentrations. In particular, 1,25(OH)₂D levels correlated with the enrichment of six bacterial taxa, all under the Firmicutes phylum, Clostridia class, and Clostridia order. Notably, all taxa were recognized as producers of butyrate.

Moreover, multivariate analysis found that higher 1,25(OH)₂D levels correlated significantly with greater α-diversity (p=7.23×10^-7). Active vitamin D also explained the greatest proportion of variation in microbial β-diversity.

“The consistency and robustness of results in finding active vitamin D metabolites associated with more favourable gut microbial diversity, including specific microbiota that are known butyrate producers, provide potential targets for intervention, whether through dietary modification and/or vitamin D supplementation in clinically appropriate populations,” the researchers said.