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Fish Oil and Blueberry Supplementation in Mild Cognitive Decline

8/28/2018 5:11:07 PM
Subjective cognitive decline refers to the self-reported decline in cognitive function without evidence of mild cognitive impairment (MCI) or Alzheimer’s disease (AD). Subjective cognitive decline increases the risk for future dementia and provides a window of opportunity to target modifiable risk factors. Diet and nutritional supplementation are important aspects of risk modification.
Epidemiological studies and clinical trials suggest that omega-3 fatty acid consumption supports cognitive function in older, nondemented adults. Also, there is clinical trial evidence that daily supplementation with blueberry juice improves cognitive performance in older adults with MCI. In this context, researchers at the University of Cincinnati conducted a clinical trial to evaluate the effects of supplementation with fish oil, blueberry powder, or both in older adults with subjective cognitive decline. 
A total of 76 men and women between the ages of 62 and 80 with mild, self-perceived cognitive decline were randomized to take fish oil, blueberry powder, fish oil + blueberry powder, or placebo for 24 weeks. Fish oil capsules (supplied by Inflammation Research Foundation, Marblehead, MA) provided 1.6 grams of eicosapentaenoic acid (EPA) plus 0.8 grams of docosahexaenoic acid (DHA) per day. Blueberry powder (supplied by US Highbush Blueberry Council, Folsom, CA) provided the equivalent of 1 cup of whole blueberries per day. Cognitive performance and laboratory analyses were assessed at baseline, 24 weeks (end of intervention), and 48 weeks (24 weeks after discontinuation of intervention).
Compared with placebo, those in the fish oil-only group and the blueberry-only group reported reduced cognitive symptoms in everyday life at 24 weeks, as measured by a validated questionnaire of working memory and executive function. These improvements were maintained at 48 weeks. Those in the blueberry-only group also reported improved discrimination in recognition memory (a function that declines in AD) at 24 weeks, but this improvement was not maintained at 48 weeks. Surprisingly, the combined fish oil + blueberry group reported no improvements in cognition at 24 or 48 weeks.
The authors admit that the lack of cognitive improvement in the combined fish oil + blueberry group was an unexpected result. They are also unable to explain why some improvements were maintained at 48 weeks while others were not. Despite these remaining questions, the results of this study provide evidence that fish oil supplementation and blueberry supplementation independently support cognitive function in older adults with subjective cognitive decline.
McNamara RK, Kalt W, Shidler MD et al. Cognitive response to fish oil, blueberry, and combined supplementation in older adults with subjective cognitive impairment. Neurobiol Aging. 2018; 64: 147-156.

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