REVIEW QUESTION

Can certain vitamins and supplements be used to prevent lung cancer?

TYPE OF REVIEW

A systematic review of 12 randomized controlled trials (RCTs).

RELEVANCE FOR NURSING

The use of vitamins, which undergo safety testing before entering the consumer market, and supplements, which are considered "food" and thus have only limited regulation, has become part of contemporary self-care. There is evidence, however, that vitamins and supplements have limited value in preventing pathophysiological processes. Vitamins A, E, C, and supplemental selenium, for example, have not been found to protect against lung cancer. And there are conflicting findings regarding the protective effect of vitamin D on developing cancer. Neither the efficacy nor the potential harm of these interventions has been substantiated in research.

Although the public may believe vitamins and supplements can have a positive effect on ailments and long-term conditions, taking them is not without risk. This review explores whether vitamins and supplements are safe and effective in lung cancer prevention.

CHARACTERISTICS OF THE EVIDENCE

This review examines the use of vitamins, minerals, and other agents, in combination or alone, in reducing lung cancer incidence and mortality in healthy people. "Healthy" was defined independent of smoking status or the presence of other lung cancer risk factors, such as exposure to asbestos.

A total of 12 studies were included in the review. It was posited that interventions described as pharmacologically active in the inhibition or reversal of carcinogenesis (for example, vitamins A, C, E, and selenium) would reduce the oxidative damage of free radicals, thereby reducing lung cancer incidence and mortality. The reviewers assessed eight of the studies to be at low risk of bias; the four remaining studies did not provide sufficient information to evaluate bias.

The primary outcomes were lung cancer incidence, lung cancer mortality, and adverse effects. Four studies included only men and five studies only women. The interventions of interest were vitamin A; vitamin C; vitamin D plus calcium; vitamin E; calcium; selenium; and combinations of vitamins A, C, and E plus selenium and zinc-all compared with placebo.

The review found no difference between the various interventions on lung cancer incidence or mortality in healthy people. However, in people who had been exposed to asbestos or who identified as smokers, vitamin A increased the risk of lung cancer incidence, lung cancer mortality, and all-cause mortality compared with placebo in three studies. Vitamin C increased the risk of lung cancer incidence in women only compared with placebo in one study. In one of five studies assessing vitamin E versus placebo, participants were found to be at higher risk for hemorrhagic stroke. Overall, the certainty of the evidence for the interventions was assessed as high.

BEST PRACTICE RECOMMENDATIONS

The authors concluded that, even considering the extremely well-designed RCTs in this review, there is no evidence that the vitamins and supplements studied prevent lung cancer incidence or associated mortality in "healthy" people.

Nurses need to help raise public awareness that vitamins and supplements have no effect on the prevention of lung cancer, and in fact may cause complications. Nurses should also raise awareness that vitamin and supplement use may interact with a patient's prescribed medication(s).

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