November 20, 2013
USPSTF: Evidence Lacking to Recommend Vitamin Supplementation in Healthy Adults
Portland, OR—For pharmacists who regularly must field questions about whether vitamin and mineral supplementation is necessary for good health, here is the latest answer from the United States Preventive Services Task Force (USPSTF): A systematic review of published studies found insufficient evidence that vitamin and mineral supplements are effective for preventing cardiovascular disease (CVD), cancer, or mortality from those diseases in healthy adults.
The report, published recently in the Annals of Internal Medicine, updated 2003 recommendations but included few significant changes. The study was primarily funded by the Agency for Health Research & Quality.
Researchers from the Kaiser Permanente Center for Health Research in Portland noted that nearly half of the U.S. population reports using a dietary supplement—at a cost of about $11.8 billion a year—with multivitamins the most frequently used supplement. They add that many animal studies indicate that the supplements protect against damaging cellular mechanisms such as inflammation, oxidative stress, and methionine metabolism, suggesting that they also would have a positive effect in humans.
In 2003, however, the USPSTF concluded that there was insufficient evidence to recommend for or against the use of vitamins A, C, and E; multivitamins with folic acid; or antioxidant combinations for the prevention of CVD or cancer.
Identifying and reviewing additional evidence on the benefits and harms of vitamin and mineral supplementation to prevent CVD and cancer in the general adult population, study authors said they continued to find that “limited evidence supports any benefit from vitamin and mineral supplementation for the prevention of cancer or CVD.” To reach that conclusion, researchers screened 12,766 abstracts and reviewed 277 full-text articles but found few of them conclusive.
“High-quality studies of single and paired nutrients (such as vitamins A, C, or D; folic acid; selenium; or calcium) were scant and heterogeneous and showed no clear evidence of benefit or harm,” according to the report. “Neither vitamin E nor beta-carotene prevented CVD or cancer, and beta-carotene increased lung cancer risk in smokers.”
Report authors note that two of the reviewed studies suggested lower overall cancer incidence in men who took a multivitamin for more than a decade, although the studies did not show similar protective effect for women or any effect on CVD.
The latest recommendations include new evidence that vitamin E is not protective against cancer or cardiovascular disease, as well as reconfirming that beta-carotene supplements alone or in combination with other supplements should not be used because of lack of benefit and the increased lung cancer risks.
The USPSTF panel cautioned that the results should not be overgeneralized and that more research is needed before it can be determined whether or not multivitamin supplementation actually is beneficial.
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