To the Editor In a recent Viewpoint,1 Dr Hellmuth and colleagues stated that “no known dietary supplement prevents cognitive decline or dementia.” We agree that there is no evidence that dietary supplements can prevent dementia, but that is partly because there have been few well-designed trials to test this idea. In trials of nutrients, a basic requirement is that to detect any benefit, the participants should have suboptimal levels of the nutrient. This requirement is often not met, and there are reports of negative outcomes in trials (and meta-analyses) in which the participants were healthy and well nourished. A second requirement is that the placebo group must show cognitive decline; again, this requirement is often not met.
Smith AD, Refsum H, Miller JW. Dietary Supplements for Brain Health. JAMA. 2019;321(24):2467. doi:10.1001/jama.2019.4963
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