Should we take a megadose of vitamin D after sunburn?

Quick boost #3 - A curious idea to examine on the summer solstice.

You are on a sandy beach in mid-June. The skies are cloudy. You know it’s pretty close to the summer solstice, but the sun’s rays do not feel particularly intense. You’re learning how to make a really good sandcastle. Towards the end of the afternoon you look down at your sandy palace with pride, and the fierce dragon that encircles it. You can imagine the fire coming from the dragon’s throat. Coincidentally you start to feel a burning sensation on the exposed skin of your shoulders and chest. You realize that you either missed a significant amount of surface area when applying sunscreen, or somehow it rubbed off. Perhaps the dragon came to life and scorched you, or more likely you sustained a pretty bad sunburn… and there is little you can do except take some ibuprofen, hydrate, and wait for the pain and redness to resolve over several very uncomfortable days.

Or should you take a one time megadose of vitamin D?

~ The above situation prompted me to recall an obscure study from 2017 in which researchers demonstrated that a one time, large dose of vitamin D3 helped limit sunburn damage if given soon after the event. In the pilot study, doses ranging between 50,000 and 200,000 IU were given one hour after a small area of exposed skin in volunteers sustained an intentional UV burn. One group received a placebo. Skin biopsies were then obtained four times between 24 hours and 1 week after the burn. Vitamin D recipients demonstrated a significant reduction in skin inflammation, visible redness, and evidence of structural skin damage on biopsy. The authors concluded:

In summary, the results of our in vivo human study, combined with animal and in vitro models, suggest that vitamin D₃ exerts immunomodulatory effects at the cellular and tissue level by selectively inducing the differentiation of anti-inflammatory, M2-macrophages.

M2-macrophages, through the expression of arginase-1, downregulation of TNF-α and iNOS, and induction of autophagy, boost the resolution of inflammation, promote tissue repair, and enhance wound healing. Thus, vitamin D₃ may serve a unique role in the skin, acting as an “endocrine barrier” to provide additional protection against environmental injury and effectively maintain skin barrier function.

The study is quite fascinating for anyone wanting a deeper dive. It was funded by the NIH, with results and commentary published in the journal DNA Cell Biology. Here is the schematic of what the study found by boosting active vitamin D3:

~ Is this study sufficient to start recommending vitamin D to everyone after a sunburn? No. Although the large dose given just after sunburn did reduce painful inflammation, and increase cellular and skin structural repair mechanisms up front, we can only speculate on what the long term risks and benefits might be. Does reducing inflammation while activating repair pathways result in a reduced risk of burn-related skin cancer, too? We would hope so. Studies have shown that vitamin D can have anti-proliferative and pro-apoptotic effects that halt cancer cells and facilitate their natural destruction. This includes melanoma cells in the lab. Or does giving vitamin D reduce the immune-mediated removal of damaged skin cells that also happens with all that redness and pain? Which side of the seesaw wins? We cannot know for certain if this large dose is a net positive in the long run without a prospective clinical trial over many years. That probably won’t happen for many years, if ever.

But in the short run it seems to work pretty well for sunburn according to this pilot study. I may have tried this once in desperation, at a dosage on the lower end. It might have produced similar results as the study noted above.

But I can say with confidence that we should be careful out there, especially now with the sun’s rays coming down in the most direct way possible in northern latitudes. Even cloudy days can result in burns. And by the way… happy first day of summer!