Summer is here, and with it comes a chance of sunburn. Not only painful, it also increases the risk of cancers like melanoma down the road. There really is no substitute for wearing sunscreen or protective clothing. However, a small but intriguing new study suggests that high doses of vitamin D may also prevent the redness and swelling associated with sunburn.
In the paper, published in the Journal of Investigative Dermatology, researchers exposed 20 volunteers to a strong light resembling solar radiation to induce a sunburn on a small patch of skin on the inner arm. They then gave them varying large doses of vitamin D immediately afterward and followed up with the participants one, two, three days and a week later to measure skin redness and thickness.
The researchers found that taking vitamin D decreased inflammation, redness and swelling, compared to taking a placebo, and the effect increased in proportion to how much vitamin D was consumed.
Taking 50,000 IU of vitamin D—a large dose, 125 times the recommended daily allowance—led to a significant reduction in redness and swelling, compared to the placebo. Likewise, those who took 100,000 IU had even less swelling, and those who took 200,000 IU had the largest reduction in inflammation.
This study, the first to show that vitamin D can reduce inflammation in the skin, suggests that it “could potentially help prevent sunburn,” says senior author Kurt Lu, a physician scientist and assistant professor at Case Western Reserve University and University Hospitals Cleveland Medical Center.
The question naturally arises: If I get burned, should I take a large dose of vitamin D? The authors don’t recommend it. “I think that’s probably not a good idea and not well established by this study, and of course the authors aren’t saying that either,” says Barbara Gilchrest, a physician scientist with the department of dermatology at Massachusetts General Hospital and Harvard Medical School, and the immediate past editor of the journal in which the study was published. She was not involved in the research, however.
Such large doses, if taken repeatedly over time, have the potential for causing vitamin D toxicity, known as hypervitaminosis D, though in the study, no participants showed any side effects. Lu made it clear that this study has no relevance for people who take daily supplements of vitamin D, which are more in the range of the 400 to 800 IU. That said, it would not be easy for most healthy people to overdose on vitamin D unless they took really excessive quantities of it, Lu adds.
It used to be thought that vitamin D was primarily involved in helping build healthy bones and muscles, but research over the past few decades has found that it plays many roles in the body, including helping regulate the immune system and influencing inflammation.
Study authors examined small sections of skin from participants and found that those with higher levels of vitamin D had more activity in a gene called arginase-1, which is involved in tissue repair and healing. (In scientific parlance, the gene was “upregulated.”) In those with lower vitamin D levels, arginase-1 was downregulated. Moreover, the authors found those who took the highest dose of vitamin D had lower levels of a protein called tumor necrosis factor, which is involved in promoting inflammation.
A small amount of exposure to UV radiation is good, because that’s how the skin naturally makes vitamin D—and this, rather than diet, is the main source for the substance. The study suggests to Gilchrest that vitamin D, even the levels of it produced in the skin, may help repair damage caused by sunburns. “Nature is wonderful in its inventiveness and to repair damage when it happens,” Gilchrest says. “Sometimes the injurious signal prompts a repair signal.”
But she reiterates that there is no “cure” for sunburn, and the best course is to avoid getting one in the first place.