An analysis conducted by scientists at the Kaiser Permanente Center for Health Research in Portland, Oregon, has reportedly concluded that "there is little evidence that vitamin and mineral supplements protect people from cancer and heart disease." Stephen Fortmann, et al., "Vitamin and Mineral Supplements in the Primary Prevention of Cardiovascular Disease and Cancer: An Updated Systematic Evidence Review for the U.S. Preventive Services Task Force," Annals of Internal Medicine, November 12, 2013. Based on these findings, the U.S. Preventive Services Task Force (USPSTF) has reportedly issued draft recommendations that echo its previous conclusion that it cannot recommend for or against taking vitamins and minerals to prevent such conditions. "At this point in time the science is not sufficient for us to estimate how much benefit or harm there is from taking vitamin or multivitamin supplements to prevent cancer or heart disease," said USPSTF Co-Vice Chair Stephen Fortmann.

According to news sources, nearly one-half of the U.S. population takes vitamin and/or mineral supplements, with the expectation that the products will prevent chronic diseases. The rationale is that heart disease and cancers, reportedly the two leading causes of death, share the risk factors of inflammation, variant methionine metabolism and oxidative stress, and that micronutrients counter these problems.

Although tests of individual nutrients in animals and in vitro evidently support the protection hypothesis, results of larger studies do not, and in 2003, USPSTF concluded that evidence was insufficient to recommend for or against antioxidant combinations—vitamins A, C and E and multivitamins with folic acid. The current analysis, which consulted 26 studies, meta-analyses, bibliographies, and government Websites and evaluated vitamins A (including β-carotene), B1, B2, B6, B12, C, D, and E, as well as calcium, zinc, iron, niacin, magnesium, selenium, and folic acid, purportedly updates and supports the 2003 recommendations.

In response to the review, Vice President of Scientific and Regulatory Affairs at the Council for Responsible Nutrition (CRN) Duffy MacKay stated that "even some, albeit limited, evidence that a simple multivitamin could prevent cancer demonstrates promise and should give consumers added incentive to keep taking their multivitamins." MacKay also noted that although there may be "limited evidence for multivitamins in preventing cancer or cardiovascular disease," CRN believes that the paucity of clinical trial evidence should not be misinterpreted as a lack of benefit for the multivitamin. "We know for sure that multivitamins can fill nutrient gaps, and as so many people are not even reaching the recommended dietary allowances for many nutrients, that’s reason enough to add an affordable and convenient multivitamin to their diets." See NutraceuticalsWorld.com, November 11, 2013; Medscape.com, November 13, 2013.