We hear about antioxidants quite regularly; they are rather fashionable these days. But what exactly are they, what do they do, and how important are they?

Antioxidants neutralise oxidants in the body, which are produced from oxygen use in the cells. Oxygen is involved in the production of energy for cells, and as such is essential for life. In the metabolism of oxygen, most is converted to harmless carbon dioxide and water, but a little is not, and instead forms oxidants called reactive oxygen species (ROS). These ROS – if not neutralised – can cause damage to cells and contribute to degenerative processes including ageing and cancer. A certain amount of ROS are natural, and indeed they play a role in normal physiology. They are involved in fighting bacteria, regulating normal cell death, and may be involved in adaptations to exercise (development of fitness). Antioxidants have a variety of functions and in addition to neutralising ROS, they dampen the cascade of ROS-induced damage, help repair damage caused by ROS and help produce an environment that favours antioxidant activity. If the body’s antioxidant capability is overwhelmed by ROS, it is said to be in a state of ‘oxidative stress’. Fresh grass is rich in antioxidants.

Antioxidants can be essential nutrients like vitamins E and C, selenium, plant constituents like bioflavonoids and compounds found in the body including glutathione and superoxide dismutase. A balanced diet is essential for adequate intake of dietary antioxidants, and for the body to make adequate antioxidants such as the latter two. The benefits of plant bioflavonoids and other dietary antioxidants are as yet, not understood and they be more important than currently thought. Vitamins C and E are important antioxidant nutrients. Vitamin C is produced in the body of a healthy horse, and supplementation is probably only necessary for sick horses and those with chronic anti-inflammatory conditions and suchlike. Vitamin E is the most important antioxidant for stabilizing cell membranes, including muscle cells. Requirements, especially for very hard working horses, are probably much higher than previously thought, and nutritionists and vets agree that a level of 3-5000 iu vitamin E per day is more appropriate for the hardest working horses, compared to the National Research Council’s 800 iu per day. Most hard working horses need to have a supplement added to even the full recommended amount of a compound feed. Vitamin E is often found in supplements together with another antioxidant nutrient – selenium.

Adequate levels of dietary antioxidants are important, but they are not a miracle cure. All horses should receive a balanced diet, which will include antioxidant nutrients, After that, more attention needs to be paid to antioxidant intake for those without access to growing grass, those in very hard work and those who are ill or recovering, all of whom may benefit from extra supplementation.