Researchers in Canada have shown how exposure to sunlight/UVB light can change the human gut microbiome, particularly in people who are vitamin D-deficient. Findings from the study in healthy human volunteers could help to explain the protective effect of UVB against inflammatory diseases such as multiple sclerosis (MS) or inflammatory bowel disease (IBD). The results, while not exactly demonstrating that the sun can shine out of your backside, are the first to show that skin exposure to UVB light alters the gut microbiome in humans, and so affects what comes out in our poop. They indicate that vitamin D mediates UVB-modulated changes in gut microbiota, uncovering the existence of a skin-gut axis that could provide new insights into approaches to managing and improving intestinal health.

The research was headed by Bruce Vallance, PhD, investigator at the BC Children’s Hospital Research Institute, University of British Columbia. Vallance and colleagues describe their work in Frontiers in Microbiology, in a paper titled, “Skin Exposure to Narrow Band Ultraviolet (UVB) Light Modulates the Human Intestinal Microbiome.”

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