Vitamin D and Gut Health – latest research

Last week my father-in-law showed me an article about sunlight, the article asks “if sunlight affects gut health?” And “if vitamin D supplements affected the gut microbiome in the same way that vitamin D from the sun does?”.

Does sunlight affect gut health? YES, it absolutely does.

Sun exposure is the catalyst that produces active vitamin D in the body.

Vitamin D is a hormone that the body requires for many optional functions and systems in the body – skin health, reproductive hormones, consistent mood, strong bones, muscle strength, thyroid hormones, and digestive wellbeing.

In recent years, the connections between autoimmune conditions such as inflammatory bowel disease (IBD) and multiple sclerosis (MS) are being investigated in more depth with links to environmental and genetic factors. Gut bacteria diversity, sunlight exposure, and vitamin D levels have been noted as influential factors for inflammatory disease. However, a new study has shown the links between all three of these elements.

Canadian researchers have recently demonstrated the exposure to UVB (Narrow Band Ultraviolet B) light directly influences gut microbiome diversity in humans. This research is looking directly at the communication between skin and gut.

So these researchers examined 21 women who were given three 60-second full-body UVB exposure sessions over 1 week. Blood and faecal samples were tested before and after to assess vitamin D levels and microbial diversity. There were 2 groups, group 1 didn’t take a vitamin supplement during winter and group 2 did.

The results revealed significant alpha and beta gut microbiome diversity in group 1 where the women did not take any vitamin D supplementation. Before UVB exposure, these women had a less balanced and diverse gut microbiome, than those taking regular vitamin D supplements.

The authors commented that UVB exposure boosted the richness of their microbiome to far greater levels than the supplemented group.

So what does this mean for you? It means that taking a supplement of vitamin D can only do so much, it means that your sunlight exposure is super important. So no more hiding from the sun because you need it to promote a happy, healthy and well balanced digestive system.

If you are deficient in vitamin supplementing can help but if you can get outside in the sunlight daily, then I highly recommend you do! How much sunlight? 10-30 minutes of direct sunlight per day is ideal… shouldn’t be too hard with summer just around the corner.





Bosman E S, et al. 2019.Skin Exposure to Narrow Band Ultraviolet (UVB) Light Modulates the Human Intestinal Microbiome. Frontiers in microbiology.