Oxygen is used abundantly during endurance exercise. The body uses it to release energy from metabolic fuels such as fat and glucose, to drive power muscle energy. However, oxygen is a volatile molecule that can generate free radicals which are associated with oxidative stress. This is damage to your body tissues that can cause chronic disease over time, as well as accelerated ageing. As your body uses more oxygen during endurance exercise it produces more free radicals. These can contribute to muscle fatigue and muscle damage, as well as inflammation which can prevent sufficient recovery for resuming exercise the next day.
Antioxidants, which are compounds found in food, are excellent at neutralising free radicals and repairing the damage they have already done to your body. Think of antioxidants as the scavengers of your body. Antioxidants are plentiful in a diet high in fresh fruit and vegetables. Nutrients which contain antioxidants include vitamins C and E and selenium. Some other nutrients which might act as antioxidants include carotenoids such as beta-carotene, isoflavones and flavonoids such as in red wine and tea.
However, a 2014 Norwegian study by Paulsen et al (1), showed that Antioxidant Supplements in the form of Vitamin C and E, taken during exercise, can weaken the mitochondria of cells. These are the cell’s ‘power stations’. The goal of endurance training is to increase the mitochondria size and number, which did not occur whilst the study participants took these antioxidant supplements. However, this study used excessive amounts of antioxidant supplements (10 times Vitamin C recommended daily intake (RDI), 25 x Vitamin E RDI). Certainly more research is needed into the use of Vitamin C and E supplements for endurance athletes.
However antioxidants consumed in normal amounts in a healthy diet (not as excessive supplements) in their natural state as fresh fruit and vegetables, are the best bet for reducing oxidative stress without running the risk of affecting the mitochondria content or size of cells.
So how do we know which foods are high in Antioxidants? Oxygen Radical Absorption Capacity (ORAC) measures the antioxidant effect of food (or more specifically the oxidation of free radicals in response to the food compounds). It’s a widely recognised measure globally.
Below is a table listing the foods highest in ORAC.