Nutritional, dietetic or nutraceutical use of red macroalgae subjected to extreme conditions of temperature and luminosity, or extracts obtained from such algae, as an antioxidant agent. An independent claim is also included for a nutritional, dietetic or nutraceutical composition, comprising red macroalgae subjected to extreme conditions of temperature and luminosity, or the extracts obtained from such algae. ACTIVITY : Anabolic. MECHANISM OF ACTION : None given.