Differential effects of low-dose and high-dose beta-carotene supplementation on the signs of photoaging and type I procollagen gene expression in human skin in vivo

Background: Although the photoprotective effects of β-carotene are thought to originate from its antioxidant properties, some studies documented pro-oxidant effects of β-carotene. Objective: Our purpose was to determine the effects of 2 different doses of dietary β-carotene on wrinkles and elasticity, procollagen gene expression and ultraviolet (UV)-induced DNA damage in human skin. Methods: Thirty healthy female subjects over the age of 50 years were randomized and received 2 different doses (30 and 90 mg/day) of β-carotene for 90 days. The baseline status was used as control. At baseline and completion of the study, facial wrinkles and elasticity were measured objectively. Buttock skin was taken to determine the type I procollagen, matrix metalloproteinase-1 and fibrillin-1 mRNA levels, and UV-induced thymine dimer and 8-hydroxy-2′-deoxyguanosine formation. Results: β-Carotene improved facial wrinkles and elasticity significantly only in the low-dose group. The minimal erythema dose decreased significantly only in the high-dose group. Type I procollagen mRNA levels were significantly increased to 4.4 ± 1.6 times the baseline level only in the low-dose group, and procollagen immunostaining increased accordingly. UV-induced thymine dimer staining was reduced in the low-dose group but tended to increase in the high-dose group. 8-hydroxy-2′-deoxyguanosine staining was significantly reduced in the low-dose group. Conclusions: 30 mg/day of β-carotene supplementation is demonstrated to prevent and repair photoaging.