This study provides strong evidence of vital interactions between high vitamin d signaling and the health of the gut microbiome in older men. The results in the finding active vitamin d metabolites associated with more favorable gut microbial diversity. 567 community dwelling men had their who had higher levels of vitamin d metabolites, vitamin d activation, & vitamin d catabolism rations, were associated with greater gut microbial diversity. Methods included stool samples from participants and full medical examinations. Other factors taken into consideration when testing included geographic region, nationality, bmi, and alcohol use. Men with highest compared to the lowest are more likely to posses butyrate- producing bacteria that are associated with favorable gut microbial health. These results support the claim the the human gut microbiome and vitamin d metabolism are inextricably linked. In one study cohort 6.7% reported recent antibiotics use in the past 30 days and gut microbial diversity was significantly reduced in these men. It’s also interesting to note, after adjustment for antibiotics use, the significant association between active vitamin d and gut microbial diversity persisted.