Vitamin Supplements Provide No Proven Cancer Prevention Benefits

Vitamins, which many consider beneficial wonder pills, are now giving scientists cause to wonder if they are as beneficial as once touted. Since the 1990s, research has suggested that vitamins hold promise in the battle against multiple cancers, heart disease, stroke, and other ailments. Researchers have studied many vitamins alone as well as in various combinations, searching for benefits that combat against a broad range of diseases.

One study found that taking more vitamin E could reduce lung cancer risks by 61 percent, while another showed that high levels of vitamin D could cut the incidence of breast cancer and the risk of dying from cancer in half. In addition, Vitamin D has been associated with the prevention of colorectal cancer and more vitamin B6 could mean less colon cancer. Even the combination of vitamin A and vitamin C administered to cultured human breast cancer cells was shown to inhibit their spread by almost 76 percent.

With all the possibilities at hand, the National Institutes of Health began conducting various long-term studies that have produced findings holding none of the previous optimism. In the Women's Health Study, 39,876 participants were followed over an average of ten years revealing that those women who took vitamin E were just as likely to develop heart disease, stroke, and multiple types of cancer as those who took a placebo. These results were published in 2005.

Later, the Women's Antioxidant Cardiovascular Study followed 8,171 participants with signs of heart disease for an average of 9.4 years to test the effects of vitamins C, E, and beta carotene. According to results published in 2007 in the Archives of Internal Medicine, none of the supplements had any effect.

In November of this year, results for the Physicians' Health Study were published in the Journal of the American Medical Association revealing that vitamins C and E did nothing to improve heart health in 14,641 male doctors followed for an average of eight years. Also in November, results published in the Journal of the National Cancer Institute for the Women's Health Initiative showed that vitamin D plus calcium did nothing to protect the 36,282 women against invasive breast cancer over a seven-year study period. However, in prior studies including these participants, supplements were found to offer a small amount of protection against hip fractures although they provided no protection for other bone fractures.

In the most recent study, known as the Selenium and Vitamin E Cancer Prevention Trial, testing in 35,533 men was done with the two supplements for a period lasting more than five years. December 2008 resulted revealed that neither supplement reduced the risks for prostate cancer. In fact, the trial was ended prematurely due, in part, to a discovery that the supplements were associated with a slight increase in the risk of prostate cancer as well as diabetes.

Other recent studies have shown that over-the-counter vitamins and minerals provide no benefit in fighting other cancers, stroke or cardiovascular disease. In fact, some research even suggests that under certain circumstances, supplements can be harmful. This has led some physicians to advise against patients taking the pills, and suggesting that they rely on a healthy diet to provide needed vitamins and minerals instead.

Scientists still maintain that vitamins are essential to good health. However, they are perplexed as to how obvious benefits from vitamins remain elusive in randomized controlled trials, known as the gold standard of modern medical research. Paul Coates, of the National Institutes of Health commented, “For drugs, someone either has (the impotence drug) Cialis in their system or he doesn't.” Yet regarding vitamins, “there's a baseline exposure that needs to be taken into account. It makes the challenge of seeing an improvement more difficult.”

Nonetheless, the belief in the benefits of vitamins has remained strong. It is estimated that 64 percent of American adults take vitamin and mineral supplements, according to The Council for Responsible Nutrition. And, according to the Nutrition Business Journal, sales have increased from $5 billion in 1995 to $10 billion in 2008 in spite of the many reports casting doubt upon their effectiveness.

According to one expert, a vitamin's benefit may become apparent only if people aren't getting enough of it, which could explain why vitamin D has been linked to a reduction in rates of heart disease, cancer and diabetes. Another school of thought is that randomized clinical trials are designed to test only one factor at a time, although vitamins and minerals work together when consumed as part of a healthy diet.

For now, researchers will revisit more traditional observational studies to continue their efforts to learn more about the nutrition’s role in fighting disease.