1. Supplementation with omega-3 fatty acids, lutein or zeaxanthin did not significantly impact the cognitive function of the elderly adults examined in this study over a 5-year period.
2. There was also no significant difference in cognitive function between study participants randomized to receive high-zinc versus low-zinc or between those randomized to beta-carotene versus placebo.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Prior studies have demonstrated variable results regarding the protective effect of nutritional supplements, including omega-3 fatty acids, lutein, and zeaxanthin on cognitive function. This study evaluated the role of these nutritional supplements on cognitive function by using data from cognitive function tests performed on participants who were enrolled in a separate trial that was examining the role of these supplements in treating age-related macular degeneration and cataracts. This study found that there was no significant effect of supplementation with omega-3 fatty acids, lutein or zeaxanthin on the cognitive function of the elderly adults examined over the 5-year period. There was also no significant difference in cognitive function between study participants randomized to receive high-zinc versus low-zinc or between those randomized to beta-carotene versus placebo.
While this study was strengthened by its randomized controlled design and high supplementation adherence rates, limitations include difficulties with generalizability given that the study design focused on a select population of elderly adults with age-related macular degeneration and cataracts. The 5-year study period may also have been too short to detect effects of nutritional supplementation on cognition. Overall, this study does not support the use of nutritional supplementation to protect against cognitive decline.
In-Depth [randomized controlled trial]: This study examined 3073 participants of the AREDS2 trial who consented to cognitive function testing and who were not eliminated by exclusion criteria aimed at eliminating participants with missing data. The mean age of participants was 72.7 years. Cognitive function testing was performed at baseline, 2 years, and 4 years. The difference between the yearly change in the composite cognitive function score of participants was not significantly different for any of the comparisons in this study, which were omega-3 versus placebo (-0.03, 99%CI -0.20 to 0.13, p = 0.63), lutein/zeaxanthin versus placebo (-0.01, 99%CI 0.87 to 1.33, p = 0.80), high-zinc versus low-zinc was (-0.01, 99%CI -0.18 to 0.16, p = 0.89), and beta-carotene versus placebo (-0.11, 99%CI -0.28 to 0.07, p = 0.12).
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