Antioxidant supplements are common and are widely regarded as safe.
This is partly because of fruits and vegetables, which are rich in antioxidants and have many health benefits.
Still, there is powerful evidence to suggest that taking high doses of antioxidant supplements can be harmful.
Increases Cancer Risk
Oxidative stress can cause damage to the cells of your body through free radicals. Thus, this is a major contributor to cancer growth (1).
Because antioxidants neutralize free radicals, it has been hypothesized that taking antioxidant supplements would reduce the risk of cancer development (2).
Multiple meta-analyses have shown that taking antioxidant supplements does not reduce the risk of many types of cancer once they have been diagnosed (3, 4, 5, 6).
They can even increase the risk of certain cancers. Several meta-analyses have found that beta-carotene, a precursor of vitamin A, increases the risk of bladder cancer and also the risk of lung cancer in people who smoke (7, 8, 9, 10).
The only exception is selenium, which may help prevent cancer in individuals with high cancer risk (11, 12, 13).
We need more research before selenium can be recommended for this reason. The harmful effects of taking antioxidant supplements overshadow their potential benefits. Therefore, taking antioxidant supplements in large doses is harmful for many reasons.
Decreases Exercise Performance
Naturally, the body produces free radicals during exercise. The harder and longer you work out, the more free radicals the body produces (14).
Since free radicals may contribute to muscle tiredness and damage, taking antioxidant supplements may reduce their harmful effects, improving performance (15).
Several studies have shown that taking large doses of antioxidant supplements like vitamins C and E can interfere with how your body adapts to exercise (16, 17, 18).
However, it even loses some exercise-related health benefits.
Get Antioxidants From Food
It is much safer and healthier to get antioxidants from food rather than supplements. All foods contain varied quantities of different antioxidants, so eating a range of meals is important.
Animal-based products, such as eggs and dairy products, have antioxidants but are not a good option.
However, antioxidants are high in plant-based foods, such as fruits and vegetables (19).
Antioxidant supplements are safe, but in large doses they can be problematic.
They can diminish the benefits of exercise and increase your risk of certain cancers.
Having the antioxidants that your body needs via a balanced diet is much better.
We strongly recommend consulting with your doctor before taking any supplements.