The invention relates to the cosmetic use or use as a food-additive of a composition that contains 7-dehydrocholesterol, a 7-dehydrocholesterol derivative, or a natural extract of a vegetable or animal microorganism containing the same, in order to protect cells against the consequences of an oxidative stress such as an exposure to ultraviolet, particularly solar, radiation, and in order to prevent the occurrence of senescent cells losing the reproductive capabilities thereof and having adverse effects on the surrounding tissues.
