Clinical Research: The Effect of DHA on Cognitive Function
Alan Gaby, MD
Author: Zhang YP, et al
Reference: Effects of DHA supplementation on hippocampal volume and cognitive function in older adults with mild cognitive impairment: a 12-month randomized, double-blind, placebo-controlled trial. J Alzheimers Dis 2017;55:497-507.
Design: Randomized, double-blind, placebo-controlled trial.
Participants: Two hundred forty Chinese individuals (mean age, 74.5 years) with mild cognitive impairment.
Study Medication and Dosage: Docosahexaenoic acid (DHA; 2 g per day) or placebo (corn oil) for 12 months.
Primary Outcome Measures: Various measures of cognitive function, and loss of volume of the hippocampus (a region of the brain involved in memory function) as determined by MRI.
Key Findings: Compared with placebo, DHA significantly improved scores in the Full-Scale Intelligence Quotient, Digit Span, and other measures of cognitive function, and significantly decreased the loss of hippocampal volume.
Omega-3 fatty acids (i.e., eicosapentaenoic acid [EPA] and DHA) play a role in normal brain function. In the present study, supplementation with DHA prevented the deterioration of cognitive function and slowed the progression of hippocampal atrophy in elderly Chinese individuals with mild cognitive impairment. Some previous studies using DHA or the combination of DHA and EPA found results similar to those of the current study.
In other research, however, these omega-3 fatty acids did not slow the progression of age-related cognitive decline. In at least one of the negative studies, habitual fish consumption was low, which suggests that the response to DHA cannot necessarily be predicted by habitual consumption of this fatty acid.
Further research is needed to determine which patients are most likely to benefit from DHA or fish oil. However, considering the other reported benefits of DHA/EPA (e.g., anti-inflammatory and cardioprotective effects), it would be reasonable to include these fatty acids as part of a comprehensive treatment plan for patients with mild cognitive impairment.