High-dose squalene ingestion increases type I procollagen and decreases ultraviolet-induced DNA damage in human skinin vivobut is associated with transient adverse effects

Evidence for beneficial effects of squalene on ultraviolet (UV)-induced photoageing of the skin is lacking.To investigate whether squalene supplementation improves signs and molecular markers of photoageing in human skin in vivo.In total, 40 female volunteers aged > 50 years received two different doses [13.5 g/day (low-dose group) and 27 g/day (high-dose group)] of squalene for 90 days. At baseline and at the completion of the study, facial wrinkles were measured using skin replicas. Skin samples were taken to compare type I procollagen and matrix metalloproteinase 1 mRNA levels by real-time reverse-transcriptase PCR, and for type I procollagen immunostaining. Skin samples were also taken 24 h after 2 x minimal erythema dose (MED) of UV irradiation before and after squalene intake to assess UV-induced thymine dimer formation and keratinocytic apoptosis.In total, 37 subjects completed the trial. Transient loose stool was experienced by 35% of volunteers in the low-dose group and 55% in the high-dose group. Facial wrinkles decreased significantly (P < 0.05) in the high-dose group, while procollagen type I mRNA levels and MED increased significantly in the low-dose group. Procollagen immunostaining tended to increase in both groups. Facial erythema decreased and pigmentation increased significantly in both groups. UV-induced keratinocytic apoptosis and thymine dimer staining were substantially reduced in both groups.Daily ingestion of 13.5 or 27 g of squalene per day resulted in antiageing effects in photoaged skin. However, in view of the frequent incidence of loose stool experienced by the subjects, the risk-benefit ratio of high-dose squalene supplementation is too high to recommend it for treating skin ageing.