Vitamin Supplements for the Prevention of Cardiovascular Disease and Cancer: Multivitamins


General

Grade: I The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the service. Evidence is lacking, of poor quality, or conflicting, and the balance of benefits and harms cannot be determined. Read the clinical considerations section of USPSTF Recommendation Statement. If the service is offered, patients should understand the uncertainty about the balance of benefits and harms.

Specific Recommendations

The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the use of multivitamins for the prevention of cardiovascular disease or cancer.

Frequency of Service

No information available.

Risk Factor Information

No information available.


Clinical

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. 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 levels, 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.

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.

Additional Approaches to Prevention

Appropriate intake of vitamin and mineral nutrients is essential to overall health. Despite the uncertain benefit of vitamin supplementation, the 2010 Dietary Guidelines for Americans 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.

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.

Rationale

No information available.


Others

An 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. 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. The American Cancer Society found that current evidence does not support the use of dietary supplements for the prevention of cancer. 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. The American Heart Association recommends that healthy persons receive adequate nutrients by eating a variety of foods rather than supplementation. The American Academy of Family Physicians' clinical recommendations are consistent with the USPSTF recommendations.


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