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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.

  • 2026-03-16
  • Photochemical & photobiological sciences : Official journal of the European Photochemistry Association and the European Society for Photobiology 25(5)
    • Aheen Faisal
    • C M Lerche
    • T Douki
    • P A Philipsen
    • C Pihl
    • T Gregersen
    • J R Granborg
    • P Bjerring
    • M Haedersdal
    • S R Wiegell

Study Design

Type
Randomized Controlled Trial (RCT)
Population
50 healthy volunteers (phototypes I-III)
Methods
In this intraindividual trial, 50 healthy volunteers were randomized (1:1) to receive either NAM (2000 mg daily) or PL (Heliocare Advanced: 480 mg daily) for 30 days
Blinding
Open-label
Duration
30 days
Funding
Unclear

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.

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