Do Antioxidant Supplements Actually Work?

fruits in container that looks like a pill pack
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Stroll through any grocery market or pharmacy, and you'll likely see antioxidant and vitamin supplements advertising health benefit. These advertisements reinforce a belief that many of us have that antioxidant and vitamin supplements are good for our health. At face value, this proposition makes sense. After all, a diet rich in antioxidants and vitamins (think green, leafy vegetables, and colorful fruits) has been shown to stave off heart disease and some types of cancer. 

However, research suggests that vitamin and antioxidant supplements in people who are not nutrient deficient confer no preventive health benefit. In other words, if you are healthy with no vitamin or mineral deficiencies, antioxidant and vitamin supplements will do little except cost you money.​

What Do Antioxidants Do?

Antioxidants are vitamins like vitamin E, vitamin C, and beta-carotene which protect the cells of the body against oxidative stress or damage caused by free radicals.

Free radicals are highly reactive molecules which mess around with various cellular structures like cell membranes, nucleic acids, and plasma lipoproteins. Free radicals are produced by our bodies during normal metabolism. When free radicals interact with antioxidants, they become stable radicals and cause no more damage.

Do Supplements Work?

In 2013, the U.S. Preventive Services Task Force (USPSTF) published results from a study examining whether vitamin and mineral supplements (including multivitamin supplements) prevent cancer and cardiovascular disease in people without nutritional deficiency.

Researchers reviewed 26 studies (24 randomized, controlled trials and 2 cohort studies) and found no evidence that such supplements help prevent cardiovascular disease, cancer and all other causes of death. Moreover, researchers found that beta-carotene supplementation may actually increase risk for lung cancer. Of note, while the results from the USPSTF study show no effects from vitamin E supplementation, another study showed that vitamin E raises mortality (death).

In light of their findings, the USPSTF went ahead and recommended against ("grade D") using vitamin E or beta-carotene supplements in order to prevent cancer, cardiovascular disease, and so forth. However, because so few high-quality studies examine preventive effects of other vitamin supplements and multivitamins, the USPSTF stopped short of recommending against their use outright and instead labeled the evidence as insufficient to make a recommendation.

In a broader sense, the USPSTF study suggesting no benefit from exogenous supplementation of vitamins and minerals in those who are healthy (not deficient in nutrients) is one of several such studies. For example, a meta-analysis done by Korean researchers suggested that antioxidants and other nutrients failed to prevent cardiovascular disease. Other recent meta-analyses have shown that nutrient supplements don't help prevent cancer either.

The Bottom Line

Thus, despite making good sense in mechanistic terms, in clinical terms, vitamin and antioxidant supplements do little to prevent disease in those without nutrient deficiency.

Researchers suggest the reason why individual supplements do little is because our physiologic systems are complex--too complex to be affected by a single vitamin or mix of a few vitamins. This hypothesis is supported by limited evidence from trials involving physiologic doses of multivitamins that contain several agents which demonstrated lower cancer incidence in men (but not women).

With the exception of studies on vitamin E and beta-carotene supplementation in healthy people, much of the research done examining preventive health effects of vitamins is deficient. Nevertheless, taken together, it's obvious to any reasonable observer that supplements do little to prevent heart disease and cancer.

So, if you're healthy and without nutrient deficiency, please save your money and don't buy such supplements. Instead, continue to partake of a balanced diet replete with fruits and leafy vegetables.

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