New Study: Vitamin C and Vitamin E Do Not Prevent Cancer

An increasing amount of evidence is emerging to disprove dietary supplement industry claims that dietary supplements — specifically large quantities of vitamins C and E — play a role in preventing heart disease, cancer and other health problems.

A large study published in the January 2009 Journal of the American Medical Association refutes the belief that vitamins can prevent cancer. In the study, 14,641 male physicians in the United States aged 50 years or older were randomized to receive either vitamin C (500 milligrams daily), vitamin E (400 International Units [IU] every other day) or a placebo.

During an average follow-up of eight years, the results were as follows:

• Vitamin E had no effect on the number of new cases of prostate cancer or total cancer compared to placebo;

• There was also no significant effect of vitamin C on total cancer or prostate cancer compared to placebo;

• Neither vitamin E nor vitamin C had a significant effect on colorectal, lung or other site-specific cancers, including bladder, pancreatic, lymphoma, leukemia and melanoma.

The study’s authors concluded that "These data provide no support for the use of these supplements in the prevention of cancer in middle-aged and older men."

Webster’s Dictionary defines vitamins as "organic substances that are essential in minute quantities to the nutrition of most animals and some plants." There is no dispute that these vitamins have nutritional benefits when consumed in small quantities as part of a balanced diet.

However, the unproven notion that larger quantities of vitamins can further improve health in people who already consume the "minute quantities" necessary for maintenance of bodily functions has been exploited by the vitamin industry. Many industry-funded health publications have touted this idea, despite the growing evidence against such a role.

Large quantities of Vitamin E pose health risks

Earlier randomized, placebo-controlled studies of vitamin E have found that using vitamin E in doses higher than 400 IU per day may result in an increased risk of death.

A different study, using 200 IU of vitamin E supplements in well-nourished people 60 or older, failed to show that vitamin E decreased the rate of acute respiratory tract infections.

However, it did show that, if a respiratory infection did occur, it was more severe than for those taking a placebo.

In another large study of women and men 55 or older at high risk for cardiovascular events (heart attacks, strokes), the use of 400 IU of vitamin E for an average of 4.5 years had no beneficial effect on cardiovascular outcomes.

Large quantities of Vitamin C are not beneficial

Vitamin C has been promoted for the prevention of an extraordinary variety of diseases including cancer, heart disease and infections such as the common cold.

But reviews of previous randomized trials comparing vitamin C to a placebo have shown that the use of large quantities of vitamin C has been fruitless.

A meta-analysis of three small trials in older adults published in a 1999 British Medical Journal article found no effect of vitamin C on decreasing mortality.

A recent study in Australia randomized people just beginning a cold to receive either 30 milligrams (one-half of the recommended daily dose and an amount the authors considered to be equivalent to a placebo), 1 gram or 3 grams of vitamin C for two days. There was no difference in the duration or severity of colds in the three groups.

In summary, as we have stated previously, "The only way to determine a beneficial effect of a supplement is through controlled scientific experiments, in which a supplement’s effects are compared with those of a placebo (dummy medication)." No extravagant claims made by manufacturers for megadoses of any vitamins have stood up to these tests.