Brief sun exposure increases the composition of health-boosting gut microorganisms, says study

UVB rays from a brief sun exposure, vitamin D and gut microorganisms have something in common: they boost good health


                            Brief sun exposure increases the composition of health-boosting gut microorganisms, says study

While taking the road to good health, remember to bask in the sun for a few minutes. A brief exposure to the sun's UVB rays help increase the composition of health-boosting gut microorganisms, suggests a new study. 

According to the research team, UVB rays from a brief sun exposure, vitamin D and gut microorganisms have something in common: they boost good health.

Though UVB rays have been associated with skin cancer, a limited exposure is beneficial. More so, in a fraction of people suffering from immune system disorders such as multiple sclerosis (MS) and inflammatory bowel disease (IBD).

"You should limit yourself to ‘sensible sun exposure’ - you only need 10-20 minutes of daily summer sun to make enough vitamin D in your skin,"  Bruce Vallance, Professor at the University of British Columbia told MEA WorldWide (MEAWW).

Previous work in rats have shown that UVB rays from lamps drive changes in the gut microorganisms, with help from vitamin D. These researchers set out to test whether the gut microbes in humans reacted to UVB rays in a similar manner.

Here, they studied for changes in microorganisms in 21 healthy female participants. Before the study, the team collected poop and blood samples to get a count of the microbial composition. Following this, all 21 participants were exposed to one-minute sessions of full-body UVB, thrice for a whole week.

Of the 21 women, 12 did not take any vitamin D supplements. As the study ended, the team again collected blood and poop samples of all the participants to check for changes in composition.

The results were similar in humans too. They saw that people who stayed away from vitamin D, showed an increase in gut microbes and also in levels of vitamin D. This shows that UVB had something to do with the change in vitamin D and microbe levels. The poop and blood samples revealed an increase in a bacteria, Lachnospiraceae, which is linked with the vitamin D status of the host, in this case, the women. 

"Prior to UVB exposure, these women had a less diverse and balanced gut microbiome than those taking regular vitamin D supplements. In this study we show exciting new data that UVB light is able to modulate the composition of the gut microbiome in humans, putatively through the synthesis of vitamin D," says Vallance.

The link between UVB and the immune system

This study could also provide insights into how UVB exposure is effective against immune system disorders. These patients are treated with UVB light coming from lamps.

"These lamps reduce the burning effects of UVB yet still cause the skin to make vitamin D. The lamps are currently used for the treatment of skin conditions like psoriasis," Vallance told MEAWW.

The treatment works because scientists have found that UVB and vitamin D influence the immune system. Vallance adds that earlier research has found a connection between the composition of a person’s gut microbiome and a person’s risk of developing immune system disorders that affect the intestine such as IBD or diseases outside the intestine, such as MS or asthma.

People with good bacteria in their guts communicate with the immune system, which, in turn, boosts their functioning. But this communication is disrupted in those suffering from immune system disorders, as they have very few of those good bacteria.

While this is known, it is unclear how UVB light is mediating these benefits through vitamin D and microbes. 

But what the study does is that it establishes a link between UVB, vitamin D and gut microorganisms. "This study shows that vitamin D is important for maintaining a healthy microbiome composition during the winter, when there is less available UVB light from the sun. Previously the ability of UVB light to affect the body at sites other than the skin was unclear. This study shows that there is a direct, and fast-acting link between UVB light and the gut microbiome through the production of vitamin D," Vallance told MEAWW.

In the future, Vallance and team will focus on how UVB light exposure alters chemicals that are produced by the gut microbes. They will also test whether UVB light leads to beneficial changes in the gut microbiome in people with inflammatory diseases such as MS or IBD and in health. 

The study was published in Frontiers in Microbiology.

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