Should we be Anti Antioxidants?

Dr. Sharon Orrange
Dr. Orrange is an Associate Professor of Clinical Medicine in the Division of Geriatric, Hospitalist and General Internal Medicine at the Keck School of Medicine of USC.
Posted on

When a patient comes in who has been taking vitamin E every day I ask them why they take it: isn’t it to prevent cancer? Turns out for vitamin E and other antioxidant supplements it may be the opposite. For years many have associated antioxidants with cancer and heart disease prevention. In fact the word “antioxidant” does as well in marketing as “natural” and “organic”. The buzz started decades ago because a diet high in vegetables and fruits rich in antioxidants is associated with a lower risk of cancer and heart disease—but taking antioxidant supplements is not. Is it too much of a good thing?

What is an antioxidant? The antioxidant vitamins include vitamin A, vitamin C, and vitamin E. Many foods, especially vegetables and fruits, also have antioxidant properties. Antioxidants are believed to help the body dispose of toxic free radicals, thereby slowing oxidative damage.

The last several years of studies have shown a lack of evidence that antioxidant vitamins are beneficial in disease prevention. Let’s take a closer look.

Vitamin A/Beta-Carotene

Vitamin A consists of preformed vitamin A (retinol) and the carotenoids such as beta-carotene. In countries where dietary intake of vitamin A is adequate (most countries) you don’t need to take vitamin A or beta-carotene supplements given the lack of any benefit and the possibility of harm. Vitamin A does not help cancer risk and in fact, studies done on vitamin A supplements and lung cancer showed those taking vitamin A had an increased risk of lung cancer. Whoops. The Physicians Health Study found that 12 years of beta-carotene supplements (50 mg every other day) produced neither benefit nor harm with respect to the incidence of cancers. Another study showed an increase prostate cancer risk if you took beta-carotene. Don’t take it.

For heart disease it was the same thing, there is no benefit of vitamin A for prevention of heart disease and one trial suggested potential harm with regard to cardiovascular mortality.

What about the eyes? Vitamin A doesn’t need to be taken for the eyes either as there is no benefit for prevention of cataracts or macular degeneration.

Vitamin C

Vitamin C has been promoted as stimulating the immune system, strengthening connective tissues, and promoting wound healing. Vitamin C may have a minor role in preventing the common cold, specifically for persons involved in high-intensity physical activity in extreme cold climates (marathoners, etc). Current evidence does not support taking vitamin C supplements for disease prevention as it has never been shown to reduce your risk of cancer. Vitamin C also does not work to prevent cataracts or macular degeneration.

Vitamin E

Despite numerous studies on Vitamin E, current evidence does not support taking Vitamin E for prevention or treatment of cancers, cardiovascular disease, dementia, or infection. Please know this: not only does Vitamin E not prevent cancer, some studies actually showed an increased risk of prostate and other cancers with Vitamin E. Vitamin E supplements also don’t protect against the development of Alzheimer disease.

What is one exception? The Age-Related Eye Disease Study (AREDS) supplement has antioxidants in it and is recommended only for folks with an early form of macular degeneration (dry macular degeneration) to help prevent the progression to visual loss. If recommended by your eye doctor you should probably listen.

Dr O.

Drugs featured in this story

Filed under