Can the Sun Modify Your Gut Bacteria?

The sunshine vitamin has unthinkable roles in our lives, from making us happier to healthier. 

Trials have shown that ultraviolet (UV) light exposure modifies the gut microbiome. Did you spend enough time under the sun this summer? If not, read below some possible consequences suffered by your gut. 

A growing body of evidence draws multiple connections between insufficient vitamin D and a long list of conditions, such as multiple sclerosis and inflammatory bowel disease. The most vulnerable categories are people living at high latitudes, where UV light can’t reach all year round.

A team of scientists, many of them from the University of British Columbia, in Vancouver, Canada, assumed the mission to answer the question: 

How UV light Affects Gut Bacteria?

The experiment was composed of 21 fair-skinned female volunteers to measure the effects of UVB exposure on the good and bad bacteria in their gut. The first group was made up of nine women that took D vitamins in the three months leading up to the trials, while the other group was D vitamin deficient. 

After three sessions of UVB exposure, the women lacking vitamin D achieved the same level of vitamin D as the ones that took supplements for months. The results appeared in ‘Frontiers in Microbiology,’ the leading journal in its field.

Prof. Bruce Vallance, the senior study author, states that before the UVB exposure, the women lacking vitamin D had a ‘less diverse and balance’ microbial bacteria. However, the scientists noticed a boost of  Firmicutes and Proteobacteria and a drop in Bacteroidetes number. 

UVB exposure boosted the richness and evenness of their microbiome to levels indistinguishable from the supplemented group, whose microbiome was not significantly changed.

While it is not clear how much time we should be spending in the sun to collect the perfect supply of vitamin D, one thing is sure: vitamin D is the only one able to have a lasting positive impact on our microbiome. 

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Comments (2)

  1. Thank you for your positive statements regarding sun exposure. Balancing the gut microbiome is only one of many positive effects of sun exposure. Here are some facts about safe, non-burning sun exposure that your readers may enjoy:
    •Seventy-five percent of melanomas occurs on areas of the body that are seldom or never exposed to sun.
    •Women who sunbathe regularly have half the risk of death during a 20-year period compared to those who stay indoors.
    •Multiple sclerosis (MS) is highest in areas of little sunlight, and virtually disappears in areas of year-round direct sunlight.
    •A Spanish study shows that women who seek the sun have one-eleventh the hip-fracture risk as sun avoiders.
    •Men who work outdoors have half the risk of melanoma as those who work indoors.
    •Women who avoid the sun have 10-times the risk of breast cancer as those who embrace the sun.
    •Sun exposure decreases heart disease risk.
    •Sun exposure dramatically improves mood.
    •Those persons who spend many hours daily outdoors have only 1/50 the risk of Parkinson’s disease!
    •For each death caused by diseases associated with sun exposure, there are 328 deaths caused by diseases associated with sun deprivation.
    •Sun exposure increases the production of BDNF, essential to nerve function.
    •Sun exposure can produce as much as 20,000 IU of vitamin D in 20 minutes of full-body sun exposure.
    •In the U.S. vitamin D deficiency in children has increased by 83 times during a 14 year period. That is likely due to indoor living and sunscreen use. More information:, and read Dr. Marc Sorenson’s book, Embrace the Sun.

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