Vitamin Supplementation to Prevent Cancer and CVD: Preventive Medication -- Healthy adults without special nutritional needs


General

Grade: D The USPSTF recommends against the service. There is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits

Specific Recommendations

The USPSTF recommends against the use of ß-carotene or vitamin E supplements for the prevention of cardiovascular disease or cancer.

Frequency of Service

No information available.

Risk Factor Information

No information available.


Clinical

Clinical Considerations

Patient Population Under Consideration

The focus of this recommendation is healthy adults without special nutritional needs. Populations studied were typically aged 50 years or older. This recommendation does not apply to children, women who are pregnant or may become pregnant, or persons who are chronically ill or hospitalized or have a known nutritional deficiency.

Suggestions for Practice Regarding the I Statement

Potential Preventable Burden

Evidence from in vitro and animal research and population-based epidemiologic studies supports the hypothesis that oxidative stress may play a fundamental role in the initiation and progression of cancer and common cardiovascular diseases.3 If this hypothesis is correct, then some combination of specific supplements, a specific dose, a vulnerable host, and specific timing may be found to be useful.

Potential Harms

Important harms have been shown with the use of β-carotene in persons who smoke tobacco or have an occupational exposure to asbestos. There are several known adverse effects caused by excessive doses of vitamins; for example, moderate doses of vitamin A supplements may reduce bone mineral density, but high doses may be hepatotoxic or teratogenic. Otherwise, the vitamins reviewed by the USPSTF had few known risks. Because many of these vitamins are fat soluble, the lifetime effect of high doses should be taken into consideration.

The USPSTF did not address doses higher than the tolerable upper intake level, as determined by the U.S. Food and Nutrition Board. Vitamins A and D have known harms at doses exceeding the tolerable upper intake levels5, and the potential for harm from other supplements at high doses should be carefully considered.

The U.S. Pharmacopeia has developed reference standards to aid in quality control of dietary supplement production; however, the content and concentration of ingredients in commercially available formulations probably vary considerably. This variability in the composition of dietary supplements makes extrapolating results obtained from controlled clinical trials challenging.

Costs

Although dietary supplements themselves are not particularly costly, the cumulative effect of this class of agent on spending is substantial. In 2010, $28.1 billion was spent on dietary supplements in the United States.6

Current Practice

Surveys conducted by the dietary supplement industry suggest that many physicians and nurses have recommended dietary supplements to their patients for health and wellness.7.

Additional Approaches to Prevention

Appropriate intake of vitamin and mineral nutrients is essential to overall health.5 Despite the uncertain benefit of vitamin supplementation, the 2010 Dietary Guidelines for Americans8 suggest that nutrients should come primarily from foods and provide guidance on how to consume a nutrient-rich diet. Adequate nutrition by eating a diet rich in fruits, vegetables, whole grains, fat-free and low-fat dairy products, and seafood has been associated with a reduced risk for cardiovascular disease and cancer.9, 10

Specific groups of patients with well-defined conditions may benefit from specific nutrients. For example, women planning or capable of pregnancy should receive a daily supplement containing folic acid to help prevent neural tube defects. The USPSTF also recommends vitamin D supplements for older persons at risk for falling.

Useful Resources

The USPSTF has a large portfolio of recommendations for prevention of cardiovascular disease and cancer, including recommendations for smoking cessation; screening for lipid disorders, hypertension, diabetes, and cancer; obesity screening and counseling; and aspirin use (available at www.uspreventiveservicestaskforce.org).

Other Considerations

Research Needs and Gaps

A critical gap in the evidence is the lack of studies of multivitamin combinations in groups generalizable to the U.S. population. Two randomized, controlled trials (RCTs) of multivitamin supplements suggest a potential cancer prevention benefit in men but not women. Future trials should be more representative of the general population, including women and minority groups, and should have enough power to show whether there are true subgroup differences. Targeting research toward persons who can be identified as high-risk for nutrient deficiency rather than the general population may be more productive.

There are substantial challenges to studying nutrient supplementation by using methods similar to those used in studying pharmaceutical interventions. New and innovative research methods for examining effects of nutrients that account for the unique complexities of nutritional research but maintain rigorous designs should be explored.

The paucity of studies and general lack of effect of any single nutrient or nutrient pair makes it difficult to draw meaningful conclusions on the balance of benefits and harms without a coordinated research effort and focus. A general lack of standardized methods to determine relevant serum nutrient levels, agreement on thresholds for sufficiency and insufficiency, or predictive validity of current mechanistic models further hinders progress in understanding potential benefits of dietary supplements.

Update of Previous USPSTF Recommendation

This recommendation updates the 2003 USPSTF recommendation on vitamin supplementation to prevent cardiovascular disease or cancer. At that time, the USPSTF concluded that the evidence was insufficient to recommend for or against the use of supplements of vitamins A, C, or E; multivitamins with folic acid; or antioxidant combinations for the prevention of cardiovascular disease or cancer (I statement). The USPSTF also recommended against the use of β-carotene supplements, either alone or in combination with other supplements, for the prevention of cardiovascular disease or cancer (D recommendation).

In the current recommendation, the USPSTF considered evidence on additional nutrient supplements, including vitamin D, calcium, selenium, and folic acid, for the primary prevention of cardiovascular disease and cancer. New evidence on the use of vitamin E increased the USPSTF's certainty about its lack of effectiveness in preventing these conditions.


Rationale

Rationale

Importance

Use of dietary supplements is common in the U.S. adult population. Forty-nine percent of adults used at least 1 dietary supplement between 2007 and 2010, and 32% reported using a multivitamin–multimineral supplement1. Supplement use is more common among women and older adults than men and younger adults2. Most dietary supplements are used to improve or maintain overall health1. The substantial effect of cardiovascular disease and cancer on health status and mortality in the United States has been well-described3, and many supplements are promoted to prevent these conditions4.

Benefits of Vitamin Supplementation

The USPSTF found inadequate evidence on the benefits of supplementation with multivitamins to reduce the risk for cardiovascular disease or cancer. The USPSTF found inadequate evidence on the benefits of supplementation with individual vitamins or minerals or functional pairs in healthy populations without known nutritional deficiencies to reduce the risk for cardiovascular disease or cancer. The USPSTF found adequate evidence that supplementation with β-carotene or vitamin E in healthy populations without known nutritional deficiencies does not reduce the risk for cardiovascular disease or cancer.

Harms of Vitamin Supplementation

The USPSTF found inadequate evidence on the harms of supplementation with multivitamins and most single vitamins or minerals or functional pairs. The USPSTF found adequate evidence that supplementation with β-carotene increases the risk for lung cancer in persons who are at increased risk for this condition. The USPSTF found adequate evidence that supplementation with vitamin E has few or no substantial harms.

USPSTF Assessment

The USPSTF concludes that the evidence is insufficient to determine the balance of benefits and harms of supplementation with multivitamins for the prevention of cardiovascular disease or cancer. The USPSTF concludes that the evidence is insufficient to determine the balance of benefits and harms of supplementation with single or paired nutrients (except β-carotene or vitamin E) for the prevention of cardiovascular disease or cancer. The USPSTF concludes with moderate certainty that there is no net benefit of supplementation with vitamin E or β-carotene for the prevention of cardiovascular disease or cancer.


Others

Recommendations of OthersAn independent consensus panel sponsored by the National Institutes of Health concluded that the present evidence is insufficient to recommend for or against the use of multivitamins to prevent chronic disease 22. The Academy of Nutrition and Dietetics (formerly the American Dietetic Association) noted in a 2009 position statement that, although multivitamin supplements may be useful in meeting the recommended levels of some nutrients, there is no evidence that they are effective in preventing chronic disease 23. The American Cancer Society found that current evidence does not support the use of dietary supplements for the prevention of cancer 10. The American Institute for Cancer Research determined in 2007 that dietary supplements are not recommended for cancer prevention and recommended a balanced diet with a variety of foods rather than supplements 24. The American Heart Association recommends that healthy persons receive adequate nutrients by eating a variety of foods rather than supplementation 25. The American Academy of Family Physicians' clinical recommendations are consistent with the USPSTF recommendations 26.


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