Lack of Efficacy, Safety Data for Dietary Supplements Frequently Used in Dermatology

Although some evidence suggests certain supplements are beneficial in addressing dermatologic issues, the use of other supplements lacks clinical support.

The efficacy and safety of zinc, biotin, vitamin D, nicotinamide, and polypodium in the management of dermatology disorders was assessed and data published in the Journal of the American Academy of Dermatology. Although evidence was sparse for most supplements, some studies supported the use of nicotinamide to prevent nonmelanoma skin cancers. Further study is needed for zinc, biotin, vitamin D, and polypodium.

In a 2011 review, as many as 66% of dermatologists recommended dietary supplements to patients, primarily for the improvement of skin, nail, and hair health. Due to their designation as “supplements,” these products can be marketed without undergoing rigorous assessment by the Food and Drug Administration (FDA). Investigators sought to review the current evidence supporting dietary supplementation for dermatologic conditions. Data were extracted from published studies which assessed zinc, biotin, nicotinamide, vitamin D, or polypodium supplementation in the management of any dermatologic condition. Studies of any design were included, including randomized controlled trials (RCTs), cohort studies, and case reports. Study outcomes of interest included supplement efficacy and adverse events. Overall, very few dietary supplements had undergone review in large-scale randomized clinical trials. Safety and efficacy evidence were limited. Few adverse events were recorded for any supplement, making safety analyses difficult. In addition, the lack of standardized dosing across trials prevented any pooled statistical analyses.

The strongest evidence for positive effects was observed for nicotinamide. In an RCT of patients with a recent history of nonmelanoma skin cancers, participants who received nicotinamide had markedly lower rates of new nonmelanoma skin cancers and actinic keratosis (AK) than participants who received placebo. Three additional studies also displayed AK lesion reductions in patients receiving nicotinamide vs placebo. Long-term safety data were not available for nicotinamide, although toxicity has been reported at doses which exceed 3.5 g/day. Some study data were available for the impact of vitamin D on melanoma risk and progression. Specifically, in vitro data suggest that vitamin D may protect keratinocytes against ultraviolet (UV)-induced apoptosis. However, RCTs of vitamin D for melanoma prevention produced mixed results. Lower vitamin D levels may predict poorer melanoma prognosis, but regular vitamin D use did not substantially lower melanoma risk.  Regarding polypodium (PLE), some studies suggest that PLE administration prior to UV exposure can prevent UV-induced erythema and idiopathic photodermatoses. PLE may also be effective in reducing AK lesions. However, further study is needed to confirm these effects. Across studies of the remaining supplements, evidence was insufficient to recommend the use of biotin or zinc.

Results from this review highlight the dearth of literature on dietary supplements in dermatology. “Large-scale randomized controlled trials investigating safety and efficacy are needed prior to widespread incorporation of these oral supplements into the general practice of dermatology,” investigators wrote.

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Thompson KG, Kim N. Dietary supplements in dermatology: a review of the evidence for zinc, biotin, vitamin D, nicotinamide, and polypodium [published online April 29, 2020]. J Am Acad Dermatol. doi: 10.1016/j.jaad.2020.04.123