Beta-Carotene and Vitamin E Not Recommended for Cancer and CVD Prevention

Between 2007 and 2010, 49% of adults in the United States reported using at least 1 dietary supplement and 32% reported using a multivitamin-multimineral supplement. In 2011, cancer and cardiovascular disease (CVD) were accountable for 22.8% and 23.7% of deaths in the United States, respectively. Using vitamins and supplements has become a common practice in preventive medicine, including the prevention of cancer and CVD.

The United States Preventive Services Task Force (USPSTF) generated evidence-based recommendations on the effectiveness of specific preventive care services. The USPSTF recently released a recommendation statement regarding the usage of individual vitamins or minerals or functional nutrient pairs for cancer, CVD, and all-cause mortality prevention [USPSTF. Evidence Synthesis. 2013;108]. Note, these recommendations do not apply to children, women who are pregnant or may become pregnant, or persons who are chronically ill or hospitalized or who have a known nutritional deficiency.

The USPSTF reviewed 24 studies on individual vitamins or minerals or functional nutrient pairs. None of the supplements studied offered any evidence of beneficial effect on cancer, CVD, or all-cause mortality. However, 2 nutrients assessed offered evidence of harmful effect or no effect on cancer, CVD, or all-cause mortality¾ vitamin E and beta-carotene.  

The USPSTF found 3 randomized, controlled trials assessing vitamin E reported CVD incidence and mortality, while 4 randomized, controlled trials reported cancer incident. In 1 trial, females in the intervention cohort reported a lower CVD mortality rate, but mortality rates for myocardial infarction and stroke, statistically, did not alter. Another trial reported an increased risk for hemorrhagic stroke in the intervention cohort.

The ATBC (Alpha-Tocopherol, Beta-Carotene Cancer Prevention) study reported a decrease in prostate cancer incidents in patients who were taking vitamin E, but the effect did not persist with follow-up [N Engl J Med. 1994;330:1029-1035]. However, the SELECT (Selenium and Vitamin E Cancer Prevention Trial) study found an increased risk for prostate cancer in patients taking vitamin E supplements after an extended follow-up [JAMA. 2009;301:39-51]. Overall, a substantial and consistent amount of studies exhibit no effect on cancer, CVD, or all-cause mortality in association with vitamin E supplementation. Therefore, the USPSTF concluded with moderate certainty that there is no net benefit and no net harm of vitamin E supplementation.

The only nutrient that possesses statistically significant data, verifying it is harmful, is beta-carotene. Recently, 2 trials reported increased risk for lung cancer and lung cancer mortality in smokers, primarily heavy smokers, who were taking a beta-carotene supplement (pooled odds ratio, 1.24; confidence interval, 1.10-1.39). It has also been shown that beta-carotene is harmful to patients who have been exposed to asbestos. The link between beta-carotene and lung cancer implies that other variables may influence beta-carotene to work either as an antioxidant or prooxidant. There is no evidence of increased risk for lung cancer in nonsmokers or patients who have not been exposed to asbestos who supplement with beta-carotene.

Only a number of studies are dedicated to individual nutrients, creating a general lack of data, which is a limitation of the study.

The updated USPSTF recommendation stated there is an insufficient amount of evidence to advocate for or against the usage of the following supplements for prevention of cancer or CVD: vitamins A, C, or E; multivitamins with folic acid; or antioxidant combinations. The USPSTF recommended with moderate certainty that patients at high risk for lung cancer should not supplement with beta-carotene. In addition, vitamin E does no harm and possesses no benefits in cancer, CVD, or all-cause mortality prevention, according to the study.