Discussion closed: vitamin supplements do not prevent or delay chronic disease
Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements
Guallar E, Stranges S, Mulrow C, Appel LJ, Miller III ER
Ann Intern Med. 2013;159(12):850-851-851. doi:10.7326/0003-4819-159-12-201312170-00011
In an editorial in today’s issue of the Annals of Internal Medicine, five physicians respond to three studies published in that same issue, which looked into the role of vitamin and mineral supplements for preventing the occurrence or progression of chronic disease. Considering the findings of these studies, the authors conclude that there is no evidence that vitamin and mineral supplements are beneficial in primary or secondary prevention of chronic disease. This is consistent with previous studies that did not find positive but possibly harmful effects.
The first publication they refer to is a systematic review of trial evidence  to update the U.S. Preventive Services Task Force recommendation on the efficacy of vitamin supplements for primary prevention in community-dwelling adults with no nutritional deficiencies. 3 trials were reviewed that studied multivitamin supplements and 24 trials of single or paired vitamins, amounting to data of over 400000 participants. The authors concluded that there was no clear evidence of a beneficial effect of supplements on all-cause mortality, cardiovascular disease, or cancer. However, they could not rule out a benefit for vitamin D, hence they called for improved studies to better assess potential harms and benefits.
The second paper is a randomised trial in which almost 6000 men aged 65 years or older took a daily multivitamin or placebo, in order to evaluate the efficacy of a daily multivitamin in preventing cognitive decline . Participants were follow-up for 12 years, after which no differences were found in overall cognitive performance or verbal memory between the multivitamin and placebo groups. These results are in line with a recent review of trials evaluating dietary supplements, none of which were found to improve cognitive function in persons with mild cognitive impairment or mild to moderate dementia.
In another trial, 1708 men and women with a previous myocardial infarction, who participated in TACT (Trial to Assess Chelation Therapy), were randomised to a 28-component multivitamin supplement or placebo . After a median follow-up of 4.6 years, no significant difference was seen between the two groups with respect to recurrent cardiovascular events. It should be noted that this study was limited by high non-adherence and a high drop-out rate.
In the editorial, the authors write that ‘despite sobering evidence of no benefit or possible harm, use of multivitamin supplements increased among U.S. adults from 30% between 1988 and 1994 to 39% between 2003 and 2006, while overall use of dietary supplements increased from 42% to 53%.’ Although a decline has been observed for use of specific individual supplements, such as b-carotene and vitamin E, after reports of adverse outcomes on lung cancer and all-cause mortality, sales of multivitamins and other supplements were not affected by major studies with null results.
The accumulated evidence is sufficient to advise against routine supplementation, the authors write. ‘We should translate null and negative findings into action. The message is simple: Most supplements do not prevent chronic disease or death, their use is not justified, and they should be avoided.‘
An exception is made for vitamin D, which requires further investigation, specifically in deficient persons. Contradicting results have been published on the use or risks of vitamin D supplementation. Despite the need for future studies to clarify its appropriate use, current widespread use is not backed by solid evidence that benefits outweigh harms.
The authors conclude that b-carotene and vitamin E and possibly high doses of vitamin A supplements are harmful. Other antioxidants, folic acids and B vitamins, as well as multivitamin and mineral supplements are ineffective for preventing mortality and morbidity due to major chronic diseases. Small benefits or harms cannot be ruled out, but clinical trials are not very suitable to identify these small effects, thus future trials addressing the use of multivitamins in the prevention of chronic disease are likely to be futile.
The authors are not beating around the bush: ’These vitamins should not be used for chronic disease prevention. Enough is enough.’
ReferencesEditorial by Gualar et al: Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements
1. 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
2. Long-Term Multivitamin Supplementation and Cognitive Function in Men: A Randomized Trial
3. Oral High-Dose Multivitamins and Minerals After Myocardial Infarction: A Randomized Trial