Antioxidants, so called because they work to counter free oxygen radicals that can damage cells, take many forms, from familiar vitamins and minerals to lesser-known phytochemicals. Fruits, vegetables, and other healthy foods are rich sources.

Research shows that the best way to obtain antioxidants is through food, not dietary supplements. This may be in part because these compounds’ benefits are complex, going beyond simply fighting free radicals, and may depend on interactions with other nutrients. It also may be that there are many oxidative processes that are critical for health, and supplements may reduce a desired level of oxidative processes.

A paper published in The American Journal of Clinical Nutrition in November 2018 bolstered the evidence for the benefits of dietary antioxidants. Researchers analyzed 69 previous large observational studies that examined dietary intakes or blood levels of major antioxidants—vitamin C, carotenoids, and vitamin E. A high intake of antioxidant-rich fruits, vegetables, whole grains, and nuts was associated with a reduced risk of cardiovascular disease, cancer, and premature death.

These positive associations are likely due to synergies among antioxidants and other potentially biologically active compounds in plant foods, according to the researchers. They noted that clinical trials on supplementation with antioxidants have mostly failed to find benefits. Other trials have actually shown added risk, and high doses can interfere with chemotherapy.