Don't rely on vitamins to ward off cancer

Summarized by Susan Aldridge, PhD, medical journalist
March 10, 2008

Summary

Vitamin supplements could protect people against cancer, thanks to their antioxidant effects. However, a new study shows that this is not so, for when a group of nearly 78,000 men and women took vitamin supplements there was no corresponding decrease in lung cancer risk and, for smokers, vitamin E even appeared to increase the risk slightly.

Introduction

Lung cancer continues to be the leading cause of cancer-related mortality in the United States and accounted for 162,460 deaths in 2006. It is well-known, of course, that smoking is the leading cause of lung cancer. But, apart from quitting, is there any other way of preventing it? Research has shown that a high intake of fruit and vegetables reduces the incidence of lung cancer. The active protective ingredients in fruit and vegetables are antioxidant vitamins C and E and folate. So it is not unreasonable to assume that taking supplements containing these might confer protection against cancer.

In fact, the evidence for the benefit of vitamin pills in cancer protection is mixed, to say the least. One often cited study¹ even suggests that beta-carotene could increase the risk of cancer. Over half the population of the United States uses vitamin supplements and it's important that they are making an informed choice. Accordingly, a team at the University of Washington, Seattle, set out to determine the long term effect of multivitamins, vitamin C, vitamin E and folate, on lung cancer risk in a large group of local residents.

What was done

A group of 77,721 men and women aged 50 to 76 from the VITAL (VITamins And Lifestyle) study took part. They gave information about their use of multivitamins, vitamin C, vitamin E and folate, in the ten years before the start of the study. The participants were then monitored for an average of four years, with cases of lung cancer being identified from the Seattle-Puget Sound cancer registry.

What was found

A total of 521 cases of lung cancer occurred during this study. Analysis showed no link between taking any of the vitamins and a decreased risk of lung cancer. For smokers, vitamin E was found to correlate with a small, but significant, increased risk of lung cancer. This increased risk was largely confined to current smokers and was greatest for non-small cell lung cancer.

What this means

People who take vitamin supplements may be intending to mimic the benefits of a healthy diet by guaranteeing an intake of what they believe to be the active components. However, it is not as simple as this. Vitamins in their natural state in fruit and vegetables may be different from vitamins packaged in a pill. There are also likely other beneficial phytochemical components in fruit and vegetables which are not captured in supplements. Therefore, doctors should counsel their patients not to rely upon vitamin pills to protect them from cancer. If the patient is a smoker, they should be reminded that quitting is their most powerful tool against lung cancer. Trying to cancel some of the harm done by smoking with vitamins has no benefit and may even be harmful. The World Cancer Research Fund and the American Cancer Society recommend two servings of fruit a day - which could decrease your risk of cancer by 20 percent. As easy as popping a pill - and a lot cheaper too!

Source

• Long-term Use of Supplemental Multivitamins, Vitamin C, Vitamin E, and Folate Does Not Reduce the Risk of Lung Cancer CG. Slatore, AJ. Littman,  et al, American Journal of Respiratory and Critical Care Medicine, 2007, vol. 177, pp. 524--530

Footnotes
1. Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis R. Bjelakovic, D. Nikolova,  et al, JAMA, 2007, vol. 297, pp. 842--857

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