To the Editor The study by Dr Chew and colleagues1 found that oral supplementation with omega-3 long-chain polyunsaturated fatty acids (LCPUFAs) or lutein/zeaxanthin had no effect on cognitive function in older persons with age-related macular degeneration. We are concerned about a number of conceptual and methodological issues.
First, the authors described this ancillary study as a randomized, double-masked, placebo-controlled, 2 × 2 factorial trial. They also stated “All participants were also given varying combinations of vitamins C, E, beta carotene, and zinc.” Therefore, LCPUFAs and lutein/zeaxanthin were not compared with a placebo. Rather, they were added to other nutrients already shown to be effective at reducing risk for central neurodegenerative disease.2- 4 A more appropriate conclusion would be that additive nutrition, in a population described as well-nourished, was not more effective than the original formulation at influencing cognitive function in older persons experiencing visual impairment.
Renzi-Hammond LM, Miller LS, Hammond BR. Oral Nutrient Supplementation and Cognitive Function. JAMA. 2016;315(5):515-516. doi:10.1001/jama.2015.16443