Trending Clinical Topic: Vitamins

Ryan Syrek


July 08, 2022

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Recent recommendations and evidence from the US Preventive Services Task Force (USPSTF) cast doubt on the efficacy of vitamin and mineral supplements. Given that the global dietary supplement market has been valued at over $150 billion, this news garnered much attention. The USPSTF's findings, along with news about the role of vitamins in other conditions, resulted in this week's top trending clinical topic. A review of 84 studies by the USPSTF found minimal benefit and some serious potential concerns (see Infographic).

Use of vitamin E and beta-carotene for the prevention of heart disease, stroke, and cancer were specifically recommended against. "We recognize that over half of people in the US take a vitamin supplement of some sort every day and 30% take a vitamin/mineral combination," USPSTF member John Wong, MD, told | Medscape Cardiology. "We looked hard for evidence, reviewing 84 studies in total. But we did not find sufficient evidence in favor of taking or not taking vitamins, with the two exceptions of beta-carotene and vitamin E, which we recommend against taking," he noted.

In an editorial accompanying the statement, Jenny Jia, MD, Natalie Cameron, MD, and Jeffrey Linder, MD — all from the Northwestern University Feinberg School of Medicine, Chicago — note that the findings included 52 additional studies that had not been available when the last USPSTF recommendation was published in 2014. F. Perry Wilson, MD, MSCE, of the Yale School of Medicine, agrees. In response to the new evidence, Wilson repeated the nephrology adage: "Vitamins give you expensive pee." He cast serious doubt about the significance of the single benefit found by the USPSTF, that multivitamins were associated with a 7% relative reduction in cancer incidence. Wilson explains that "relative risks really tend to overstate the effect size. In absolute terms, multivitamins reduced the incidence of cancer by around 0.2%. That means you'd need to treat 500 people with a multivitamin to avoid one case of cancer."

Outside of the USPTSF research, vitamin C had more disappointing news in another study. More patients in septic shock who received vitamin C infusions died or experienced greater organ dysfunction than those who received placebo, according to an article published in The New England Journal of Medicine. The findings come from LOVIT, a randomized, placebo-controlled trial of 863 patients in Canada, New Zealand, France, and other countries. In the study, 429 patients were randomly assigned to receive a vitamin C infusion every 6 hours for 4 days, and 434 were assigned to receive placebo. At 28 days, 191 of 429 patients (44.5%) in the vitamin C group had died or had persistent organ dysfunction, compared with 167 of 434 (38.5%) in the placebo group. This amounted to a treatment effect of 1.21 (P = .01). "This was an unexpected finding, and the secondary analyses — which included the evaluation of five biomarkers of tissue dysoxia, inflammation, and endothelial injury measured up to day 7 — did not determine a putative mechanism for harm," say the researchers, led by François Lamontagne, MD, associate professor and intensivist at the University of Sherbrooke in Quebec, and Neill Adikhari, MDCM, associate professor in critical care at the University of Toronto.

Correcting vitamin deficiencies remains important. Vitamin D deficiency was recently found to significantly increase the risk for miscarriage. In an analysis of 10 studies, women who were vitamin D deficient (< 50 nmol/L) had nearly a twofold increased risk for miscarriage compared with women who had sufficient vitamin D levels (> 75 nmol/L; odds ratio, 1.94; 95% CI, 1.25 to 3.02). Low vitamin D was also recently associated with a higher prevalence of diabetic foot ulcers in elderly patients in a preprint study not yet peer-reviewed.

On the other hand, supplementation with vitamin D was recently found to be ineffective in reducing the risk of developing type 2 diabetes in the general population with prediabetes. The new findings come from the prospective Diabetes Prevention With Active Vitamin D (DPVD) trial of more than 1200 Japanese participants with impaired glucose tolerance. Treatment with 0.75 μg/d of eldecalcitol, an active vitamin D analog, for 3 years did not prevent progression from prediabetes to type 2 diabetes, nor did it improve the rate of regression to normoglycemia compared with placebo.

Nearly 60% of the US public uses some form of dietary supplement, many for cardiovascular disease (CVD) prevention. The editorialists who wrote in response to the USPSTF suggest that the recent evidence confirms that the appropriate strategy is not to focus on vitamin supplements but to emphasize lower-risk, higher-benefit activities like a healthy diet, routine exercise, maintaining a healthy weight, and avoiding smoking. Still, research regarding vitamin supplementation is likely to always be met with great interest, as it was this week.

Learn more about CVD prevention.


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