A Randomized Clinical Trial: Daily Photoprotection With a Combined Sunscreen-Antioxidant Formulation Preserves Mitochondrial DNA Integrity in Human Facial Skin In Vivo.

Abstract

Objective: To evaluate whether a daily antioxidant-enriched sunscreen preserves mitochondrial DNA (mtDNA) integrity vs vehicle, whether habitual sunscreen users gain additional protection from antioxidants, and whether mtDNA swabs can detect individual-level responses.

Methods: Adults completed a randomized, double-blind, vehicle-controlled 12-week trial. Cheek swabs collected at baseline and Week 12 underwent blinded quantitative polymerase chain reaction assays. mtDNA damage was expressed as ΔCt, where higher values indicate greater damage and a negative change reflects improved integrity. The primary outcome was change in ΔCt.

Results: Forty-one participants provided valid samples (antioxidant sunscreen: n=19; vehicle: n=18). Mean ΔCt change favored the antioxidant sunscreen (-0.48 vs 0.35; P=0.06; Mann-Whitney U, P=0.07). Responder rates were higher with antioxidant sunscreen (73.7% vs 38.9%; Fisher exact, P=0.05). Among habitual sunscreen users, mtDNA integrity improved with antioxidant enrichment (median ΔCt: -0.67; P=0.04) and worsened with vehicle (median ΔCt: 0.58; P=0.03). In this subgroup, responder rates were also higher with active treatment (75% vs 25%; P=0.03). mtDNA integrity demonstrated a clear individual-level sensitivity to change.

Limitations: This was a single-site pilot study and lacked a no sunscreen-only comparator arm.

Conclusion: Daily use of an antioxidant-enriched sunscreen produced consistent molecular evidence of reduced mtDNA damage, including statistically significant within-participant improvement among habitual sunscreen users.