Trial reportPhotochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology2026
Changes in ultraviolet a radiation-induced thymidine dimers and erythema after oral nicotinamide or polypodium leucotomos extract in healthy volunteers: a randomized intraindividual trial.
Trial report in Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
backgroundNicotinamide (NAM) and Polypodium leucotomos extract (PL) have demonstrated photoprotective effects, but their role in preventing UVA-induced DNA damage in humans remains unclear.
objectiveTo evaluate the effects of oral NAM and PL on UVA-induced erythema and thymidine dimer (TT-dimer) formation.
methodsIn this intraindividual trial, 50 healthy volunteers (phototypes I-III) were randomized (1:1) to receive either NAM (2000 mg daily) or PL (Heliocare Advanced: 480 mg daily) for 30 days. UVA-induced erythema, assessed by minimal erythema dose (MED), and TT-dimers, quantified in urine and skin biopsies, were measured before and after treatment with NAM or PL.
resultsBoth NAM and PL increased MED by 26%. With a median MED of 27.7 J/cm² (13.4-51.1 J/cm²) pre-NAM and 34.8 J/cm² (13.4-62.5 J/cm²) post-NAM (p = 0.0008). And A median MED of 27.7 J/cm² (13.4-51.1 J/cm²) pre-PL and 34.8 J/cm² (16.4-62.5 J/cm²) post-PL (p = 0.0002). Neither treatment reduced UVA-induced TT-dimers in skin (NAM: p = 0.15; PL: p = 0.15) or urine (NAM: p = 0.89; PL: p = 0.30). LIMITATIONS: NAM and PL were not administered during the urine collection-period, which limited the assessment of the treatment's effect after radiation.
conclusionUVA-induced erythema was significantly reduced by PL and NAM, but neither had measurable effects on TT-dimer induction. Further research should investigate the relation between these findings and the chemopreventive effect of NAM and PL on skin cancer.
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