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Background <p>Nicotinamide (NAM) and Polypodium leucotomos extract (PL) have demonstrated photoprotective effects, but their role in preventing UVA-induced DNA damage in humans remains unclear.</p> Objective <p>To evaluate the effects of oral NAM and PL on UVA-induced erythema and thymidine dimer (TT-dimer) formation.</p> Methods <p>In this intraindividual trial, 50 healthy volunteers (phototypes I–III) were randomized (1:1) to receive either NAM (2000&#xa0;mg daily) or PL (Heliocare Advanced: 480&#xa0;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.</p> Results <p>Both NAM and PL increased MED by 26%. With a median MED of 27.7&#xa0;J/cm² (13.4–51.1&#xa0;J/cm²) pre-NAM and 34.8&#xa0;J/cm² (13.4–62.5&#xa0;J/cm²) post-NAM (<i>p</i> = 0.0008). And A median MED of 27.7&#xa0;J/cm² (13.4–51.1&#xa0;J/cm²) pre-PL and 34.8&#xa0;J/cm² (16.4–62.5&#xa0;J/cm²) post-PL (<i>p</i> = 0.0002). Neither treatment reduced UVA-induced TT-dimers in skin (NAM: <i>p</i> = 0.15; PL: <i>p</i> = 0.15) or urine (NAM: <i>p</i> = 0.89; PL: <i>p</i> = 0.30).</p> Limitations <p>NAM and PL were not administered during the urine collection-period, which limited the assessment of the treatment’s effect after radiation.</p> Conclusion <p>UVA-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.</p>

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Changes in ultraviolet a radiation-induced thymidine dimers and erythema after oral nicotinamide or polypodium leucotomos extract in healthy volunteers: a randomized intraindividual trial

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  • 发表日期：

    2026年3月16日

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  • Aheen Faisal,
  • C. M. Lerche,
  • T. Douki,
  • P. A. Philipsen,
  • C. Pihl,
  • T. Gregersen,
  • J. R. Granborg,
  • P. Bjerring,
  • M. Haedersdal,
  • S. R. Wiegell

摘要

Background

Nicotinamide (NAM) and Polypodium leucotomos extract (PL) have demonstrated photoprotective effects, but their role in preventing UVA-induced DNA damage in humans remains unclear.

Objective

To evaluate the effects of oral NAM and PL on UVA-induced erythema and thymidine dimer (TT-dimer) formation.

Methods

In 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.

Results

Both 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.

Conclusion

UVA-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.