Antioxidant

An antioxidant is any compound that neutralises reactive oxygen species, the reactive molecules produced continuously as a by-product of using oxygen. The body makes its own, including glutathione and enzymes such as superoxide dismutase, and food supplies others including vitamins C and E and a wide range of plant polyphenols.

The word became a marketing category because the underlying story is so appealing: reactive species damage cells, ageing and disease involve that damage, therefore mopping them up should help. Large trials of antioxidant supplements have mostly failed to deliver on that logic, and some have found harm, notably beta carotene in smokers.

The reason is that reactive oxygen species are also signals. They are part of how the immune system kills pathogens and how muscle registers that it has been trained, so blanket suppression removes messages as well as damage.

That matters directly for training. High dose vitamin C and E around exercise can blunt some of the adaptations training is meant to produce, which makes routine megadosing around sessions an actively poor idea rather than a neutral one.

Whole foods behave differently from isolated compounds. Fruit, vegetables, herbs, tea, coffee and cocoa supply mixtures at modest doses alongside fibre and micronutrients, and the outcome evidence for eating them is strong where the evidence for extracting one component and selling it at twenty times the dose is not.

Antioxidant capacity scores on packaging, such as ORAC values, were withdrawn by the US Department of Agriculture years ago as misleading, since a test tube measurement predicts nothing about what happens in a person.

In practice, eat plants, do not take high dose antioxidant supplements around training, and treat the word on a label as a marketing term rather than a health claim.