A worldwide rise in immune and inflammatory diseases such as multiple sclerosis and inflammatory bowel diseases has been linked to Western society-based changes in lifestyle and environment. These include decreased exposure to sunlight and the resultant impairment in the production of vitamin D, as well as dysbiotic changes in the makeup of the gut microbiome. Despite this fact, it is still unclear if there are any direct links between sunlight/UVB light and the gut microbiome.
Sunlight affects the microbiota
Now, a study from researchers at the University of British Columbia shows how exposure to sunlight can change the human gut microbiome, specifically in people who are vitamin D-deficient. The team states their findings in healthy human participants could help to explain the protective effect of UVB against inflammatory diseases such as multiple sclerosis or inflammatory bowel disease. The opensource study is published in the journal Frontiers in Microbiology.
Previous studies show there are high rates of vitamin D deficiency in people who live in locations with long winter seasons, where the lack of UVB from sunlight means they don’t produce enough of the vitamin. Limited UVB exposure is one of the most important environmental factors linked to the onset of immune-mediated chronic inflammatory diseases such as multiple sclerosis and inflammatory bowel diseases.
Vitamin D is also known to promote intestinal health, with vitamin D deficiency shown to promote dysbiosis of the gut microbiota, even in healthy individuals. However, it’s still unclear if there is a direct association between UVB light and human intestinal microbiota. The current study investigates whether exposing the skin to UVB light to increase vitamin D levels would also affect the makeup of the human intestinal microbiota.
The current study exposes the skin of 21 healthy female human volunteers to UVB light to see whether increasing vitamin D levels changes the makeup of intestinal microbiota.
Nine of the participants took vitamin D supplements during the three months before the start of the trial, whilst the rest of the participants did not. Results show the majority of the participants who took supplements were vitamin D-sufficient at the start of the trial, whereas most of the group who did not take supplements were vitamin D-insufficient before the trial started.
Data findings show skin UVB ray exposure only significantly increases gut microbial diversity in the 12 subjects who were Vitamin D deficient at the start of the study. The lab states that prior to UVB exposure, these women had a less diverse and balanced gut microbiome than those taking regular vitamin D supplements.
Proving there is a skin-gut axis
They go on to add UVB exposure boosted the vitamin D deficient participant’s microbiome to levels indistinguishable from the supplemented group whose microbiome was not significantly changed; microbiota species boosted in the study included Lachnospiracheae, Rikenellaceae, Desulfobacteraceae, and one group of Clostridiales.
The team surmises they have proven the effect on the microbiota composition after repeated UVB/sunlight exposure, specifically for subjects suffering from Vitamin D insufficiency. For the future, the researchers state proving the existence of this novel skin-gut axis could be used to promote intestinal homeostasis and health.
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