Moreover, the assumption that antioxidants, such as beta-carotene, may protect against ageing is unconfirmed.
Researchers in Australia tested whether regular use of sunscreen compared with discretionary use or use of beta-carotene supplements retarded skin ageing compared with placebo, as measured by degree of photoageing.
A total of 903 male and female subjects aged <55 years were assigned to four study groups: daily use of broad-spectrum SPF 15+ sunscreen and 30mg of oral beta-carotene; daily use of sunscreen and oral placebo, discretionary use of sunscreen and 30mg of beta-carotene, and discretionary use of sunscreen and oral placebo.
Skin ageing from baseline to the end of the trial was 24% less in the daily sunscreen group than in the discretionary group. However, beta-carotene had no overall effect on skin ageing in the study population.
Hughes MCB, Williams GM, Baker P et al. Ann Intern Med 2013; 158: 781-90