Dr. InYoung Kim, a dermatology resident, and Dr. Jeffrey Scott, a fellow in Mohs surgery and dermatologic oncology, both at Case Western Reserve University and University Hospitals Cleveland Medical Center and both editorial contributors to PracticeUpdate, discuss the results of a recently published study in which Dr. Scott was involved, which found that sunburn-associated inflammation can be reduced rapidly through an oral dose of vitamin D.1
Dr. Kim: Congratulations on this very impactful study! Will you tell us what your study showed?
Dr. Scott: Thank you. Our study investigated whether oral vitamin D can help reduce inflammation from sunburn. We found that the intensity of sunburn could be reduced if participants were given high-dose vitamin D 1 hour after receiving experimental sunburn. Specifically, the redness, swelling, and various inflammatory markers in the skin were lower after vitamin D treatment.
Dr. Kim: High-dose vitamin D? How high were the doses? And how was it given?
Dr. Scott: Yes; it was a one-time high dose of oral vitamin D. We gave the participants up to 200,000 IU of vitamin D.
Dr. Kim: Is that a safe dose? Standard over-the-counter supplements are only 1000 to 2000 IU per pill.
Dr. Scott: Yes; it is actually a safe dose. Typically, we think of vitamin D as being administered in doses of 50,000 IU once weekly or up to 2000 IU every day; so, the dose we administered was between 4 and 10 times these standard supplementation doses. I want to emphasize that vitamin D was given as a one-time dose in our study, just after sunburn. There were no serious adverse events for any of the participants, and we also measured calcium and vitamin D levels in the participants’ blood. We found that the serum calcium and vitamin D levels remained within normal reference ranges throughout the study period. Most of the participants began the study with serum vitamin D levels that would be considered insufficient or deficient, and the vitamin D dose we administered increased their serum vitamin D levels into what we would consider a sufficient range; but, importantly, not into a toxic range. Therefore, our study showed that a one-time high-dose of 200,000 IU is quite safe.
Dr. Kim: I see. Good to know that it’s safe! I’m interested in how this all started. Where did the idea come from, and how did you begin studying this specific topic?
Dr. Scott: The lab, led by Dr. Kurt Lu, is interested in mouse models of skin inflammation and how vitamin D modulates immune responses and wound healing. Specifically, Dr. Lu’s lab has been working on a mouse model of chemically induced skin injury, and we have shown that mice that receive vitamin D right after skin injury induced by nitrogen mustard had less skin inflammation, less skin damage, and, interestingly, were less likely to die from the systemic effects of nitrogen mustard exposure. The notion that vitamin D can act in mice to suppress skin inflammation from a chemical exposure gave us the idea that this same biology could also be applied therapeutically to treat acute inflammatory insults in humans, such as sunburn and thermal burns.
Dr. Kim: What would you want your readers to take away from this study? What are the big-picture implications?
Dr. Scott: First, I want to emphasize that this was a pilot study with 20 participants. The design was definitely a strength of the study, as it was a randomized, double-blind, placebo-controlled trial, and the results are very interesting. However, larger clinical trials are going to be required to reproduce these findings before any large-scale recommendations can be made regarding vitamin D use for its anti-inflammatory properties.
Nevertheless, I think these results strongly support the fact that vitamin D has diverse effects in the body besides just calcium and bone health. Vitamin D modulates immune responses and has important roles in skin homeostasis. Interestingly, we also use energy from sunlight to produce vitamin D locally within the skin. The results from our study suggest potential evolutionary implications for local vitamin D production in skin. It may be that vitamin D acts within the skin to maintain homeostasis and reduce inflammation following environmental insults.
Dr. Kim: Interesting! It’s embarrassing to admit, but even as a dermatologist, I find it hard to wear sunscreen every day. With the findings from your study, can we just pop a pill and forget the sunscreen? That would be so easy!
Dr. Scott: I would definitely not recommend substituting your sunscreen use for vitamin D. We still recommend daily sunscreen use because, ideally, we would never want sunburn to occur. In our study, we gave vitamin D after sunburn had already occurred; so, it was a post-exposure dose and not a prophylactic dose. There are no data on whether vitamin D can be given prophylactically to prevent sunburn, like sunscreen. Our study shows that once sunburn has already happened, there may be interesting biology with regard to vitamin D reducing skin inflammation.
It is safest not to get sunburned in the first place, and we recommend vigilant sun protective behavior including daily sunscreen use, avoidance of midday sun, seeking shade, and wearing sun-protective clothing.
Dr. Kim: If vitamin D reduces inflammation, does this mean that it has the potential to increase the risk of skin cancer down the line, since we need a strong immune response to clear cancer?
Dr. Scott: That’s a very interesting thought. We’ve been considering this idea, but we didn’t specifically address it our study. If skin inflammation is important in clearing sun-damaged, and therefore DNA damaged, cells, then suppressing inflammation with vitamin D following sunburn may allow these damaged cells to remain in the skin and have a higher risk for turning into skin cancer. This idea needs further investigation, and it further reinforces that sun-protective behavior is critical for preventing sunburn. Vitamin D may reduce sunburn, but it’s best to not have the sunburn occur in the first place.
Dr. Kim: So, what’s next in line for your lab?
Dr. Scott: The next step will be to reproduce these findings in larger studies. Ultimately these results need to be replicated in diverse populations to ensure that the finding can be validated before the therapeutic use of vitamin D for its anti-inflammatory properties can be recommended for clinical use. We also want to determine if baseline vitamin D levels have an impact on how well this high dose of vitamin D works in suppressing inflammation. For example, does someone need to be vitamin D–deficient or insufficient for this high dose to be effective, or is there some necessary amount of vitamin D that needs to be present for this high dose to be effective? In addition, we want to expand these findings and investigate if vitamin D reduces skin inflammation after other environmental insults, including thermal burns and chemically induced skin injury.
Dr. Kim: Wow, so many patients can definitely benefit from that!
Dr. Scott: Yes. Vitamin D is a safe, cheap, and simple therapy; so, we believe that its anti-inflammatory therapeutic implications are broad.