Do you know about the vitamin D-sunlight and gut connection?

It’s not uncommon for many people to say that they suffer assorted symptoms, such as lethargy and depression, as the days get shorter but new research shows that the lack of sunlight affects so much more.

There appears to be a connection between skin exposure to UVB light and the microbiome – that mix of bacteria in your gut. A healthy microbiome contains not only a higher amount of beneficial bacteria but also diverse bacterial species. Different types of bacteria offer assorted health perks ranging from better immune system function, decreased risks of various diseases including certain cancers, easier weight management and even a defense against depression.

Optimal immune system functioning includes fighting off infections such as seasonal flus (get the flu shot too!) but also autoimmune disease like multiple sclerosis and inflammatory bowel disease.

Enter vitamin D
Animal research has shown that vitamin D plays a role in maintaining a balance of healthy bacteria in the gut. Vitamin D is produced when bare skin is exposed to ultraviolet light of sufficient intensity. Note the bare skin part. If you wear sunscreen, then the production of vitamin D is blocked. But hey, if you live in Canada or in other northern climes, at this time of year, the sun isn’t strong enough to produce vitamin D anyway. Between protecting your skin in the summer and the lack of sunshine at other times of year, vitamin D supplementation is the smart way to go.

And this new research, from the University of British Columbia, is pointing to just how smart it is.

While the study, published in Frontiers in Microbiology, was small, it adds to the body of evidence showing the importance of vitamin D.

Healthy female volunteers were divided into 2 groups: those that took vitamin D supplements (average dose, 1389 IU) throughout the winter prior to the start of the study and those who did not. All participants were given three one-minute sessions of full-body UVB exposure in a single week. Before and after the light treatment, stool samples were taken for analysis of gut bacteria along with blood samples for vitamin D levels.

The researchers found that skin UVB exposure significantly increased gut microbial diversity, but only in subjects who were not taking vitamin D supplements during the (winter) study.

“Prior to UVB exposure, these women had a less diverse and balanced gut microbiome than those taking regular vitamin D supplements,” reports Professor Bruce Vallance, who led the University of British Columbia study. “UVB exposure boosted the richness and evenness of their microbiome to levels indistinguishable from the supplemented group, whose microbiome was not significantly changed.”

The bottom line
But as often the case with nutrition, it’s about the whole picture. It’s not just taking your vitamin D or probiotic and fermented foods. Filling your plate with healthy selections including a range of fibre-packed foods – plenty of vegetable, fruits, pulses, whole grains and nuts and seeds – will also provide the prebiotic fuel to keep your beneficial bacteria happy and well-fed.

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Categories: Food Safety, Nutrition News

Author:Rosie Schwartz

Rosie Schwartz is a Toronto-based consulting dietitian and writer.

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