Carotenoids in evolutionary ecology: re-evaluating the antioxidant role.

The antioxidant role of carotenoids in the living organism was proposed as a possible basis for the honesty of carotenoid-based signals. However, recent studies have questioned the relevance of carotenoids as powerful antioxidants in vivo. Current evidence does not seem to support the "antioxidant role" hypothesis, but it does not allow us to reject it either. This paper proposes some steps to solve this controversy, such as taking a dynamic approach to antioxidant responses, designing protocols that expose individuals to oxidative challenges, analyzing tissues other than blood, and obtaining measures of antioxidant capacity and oxidative damage simultaneously. However, it should be considered that, irrespective of their antioxidant potential, carotenoids might still give information on oxidative stress levels if they are particularly sensitive to free radicals. Finally, lumping together the immunostimulatory and antioxidant roles of carotenoids should be avoided as these functions are not necessarily associated.