VANCOUVER, CANADA — Exposure to ultraviolet rays may increase biodiversity of the gut microbiome in humans.

Canadian researchers find that being under the sun could enrich gut flora and that a novel skin-gut axis may exist, according to a study published in Frontiers in Microbiology on October 24.

The researchers say that 21 women volunteers were subjected to three full body exposures to UV rays over one week.

Blood samples were tested for vitamin D levels and stool samples were tested for the biodiversity of their gut bacteria.

Frontiers Science News reports that half of the participants who regularly took vitamin D supplements experienced no changes to their gut microbiome.

However, women who did not take supplements saw increases to vitamin D levels, and their gut microbiome became as diverse as the supplemented group.

The researchers state that multiple sclerosis and inflammatory bowel diseases are associated with the lack of sunlight, vitamin D, and unhealthy gut microbiota.

The study indicates that there is a direct link between those factors, but it does not identify the causal mechanism.