About half of Americans take dietary supplements, but this practice does not appear to reduce the incidence of tumors or cardiovascular disease. In its recent report, the U.S. Preventive Services Task Force concluded that there is not sufficient evidence that vitamins help prevent tumors or cardiovascular disease. In addition, the USPSTF does not recommend taking beta carotene or vitamin E. The evidence level for this recommendation is D. USPSTF co-chair Michael LeFevre, PhD, noted that there is evidence that vitamin E is not beneficial and that beta carotene may increase the risk of lung cancer in certain populations. The report, published in the February 25 issue of the Annals of Internal Medicine, is an update of the 2003 recommendations, and Dr. LeFevr noted in a statement that, given the uncertainty of vitamin supplementation in the prevention of oncology and cardiovascular disease, it is important for health care providers to take into account a patient’s medical history, the value of applying nutritional supplements, and the patient’s personal preferences when discussing nutritional supplements with patients in order to make the best judgment. In order to make the best judgment. Unlike the 2003 USPSTF recommendations, this update values the evidence for other dietary supplements, such as vitamin D, calcium, selenium, and folic acid, as primary prevention of oncology or cardiovascular disease. Also, this update takes into account the evidence for the application of vitamin E. The evidence supporting its ineffectiveness in preventing tumor and cardiovascular disease has increased. Some Conflicting Data USPSTF recommendations are based on the published literature on vitamins and their health effects. A number of studies in recent years have evaluated the benefits and harms of vitamin supplementation, but the results have been mixed. A recent meta-analysis of 26 studies showed that vitamin and/or mineral supplements did not have a protective effect against tumors or cardiovascular disease. Data from an earlier large clinical study on women’s health showed that multivitamin use did not have any effect on the risk of tumors, cardiovascular disease, or overall mortality in women. However, two studies examining the relationship between multivitamins and breast cancer found opposite results, with one study finding that multivitamin use increased the risk of breast cancer and the other finding that it decreased the risk of breast cancer. Another study, conducted in 2012, showed that taking a daily multivitamin reduced the risk of tumors and death from tumors in men. Notable limitations Dr. BalzFrei, a leading professor of biochemistry and biophysics at Oregon State University, believes that the studies evaluated by the USPSTF have some obvious limitations that were not mentioned in the updated recommendations. Many of these studies were shorter and had older subjects.” Another limitation is that the USPSTF evaluates studies with different dietary interventions together, which use different study designs, study endpoints and data formats, said Dr. Frei, director and tenured chief professor of the Linus Pauling Institute. In addition, the USPSTF focused only on primary evidence of dietary supplements for the prevention of oncology and cardiovascular disease, and did not review the evidence on whether dietary supplements can be used to maintain normal physiological function or to supplement dietary deficiencies in the general American population. Dr. Frei and colleagues agree that the current evidence is insufficient to evaluate the benefits and harms of taking dietary supplements in oncology and cardiovascular disease. They also agree with the USPSTF that beta carotene can increase the risk of lung cancer in people at high risk for the disease, and that supplementation with vitamin E and beta carotene alone does not prevent the development of tumors and cardiovascular disease. Dr. Frei notes, “Daily multivitamins are a safe, simple, and relatively economical way to compensate for vitamin deficiencies and improve micronutrient status in the United States. Adequate micronutrient intake is necessary to maintain normal physiological function and metabolism and to maintain overall health of the body. Shortcomings known, much more needs to be done From the update of this report, it appears that the shortcomings of previous studies and the general lack of data on the efficacy of single nutrients or pairs of nutrients make it difficult to draw meaningful conclusions about their benefits or harms without consolidating research efforts and concerns. The general lack of standard methods for determining relevant serum nutrient levels, inconsistent criteria for adequacy versus deficiency, and the low predictive validity of existing mechanistic models have hampered our understanding of the potential benefits of dietary supplements. The USPSTF emphasizes that in vitro experiments and population-based epidemiological studies support the hypothesis that oxidative stress plays an important role in the development and progression of tumors and common cardiovascular diseases. If this hypothesis is correct, there may be benefit in giving a given supplement at a certain dose, taking into account individual factors as well as the timing of administration. While the risk factors for cardiovascular disease are well established, the risk factors for tumors are much more complex and are influenced by tumor heterogeneity, environment and genetics, the group wrote. The antioxidant and anti-inflammatory effects of multiple nutrients are the basis for their recommendation for the prevention of cardiovascular disease and tumors. Studies have shown that the antioxidant properties of antioxidants vary with nutrient concentrations and other oxidants/antioxidants. Thus, the USPSTF states that the correlation between beta carotene and lung cancer in high-risk populations suggests that the presence of other factors can influence the effects of beta carotene, which may act as both an antioxidant and a pro-oxidant. In disseminating this information, the USPSTF also acknowledges that the “lack of key evidence” means that the studies that have been conducted are not representative of the entire U.S. population. For example, two randomized controlled studies have shown multivitamins to be beneficial in preventing tumors in men, but not in women. The USPSTF noted that future trials should be more representative of the population as a whole and need to have sufficient efficacy to confirm whether there are indeed differences between subgroups. The Task Force also acknowledged the challenges of studying the effects of nutrient supplementation in a manner similar to that used to study drug therapy.