DHA Supplementation Improves Memory in Young Adults
Stonehouse ,W. et al., American. J. of Clinical Nutrition, 97: 1134-1143 , 2013
Institute of Food, Nutrition and Human Health, Massey University .Auckland, New Zealand
In view of the critical role of DHA omega-3 in brain functioning, the present study was aimed at investigating the potential benefit of DHA supplementation on cognitive functioning in young adults (with a low dietary intake of long-chain omega-3 fatty acids - less than 200 mg of DHA plus EPA per week). The authors pointed out that previous trials with DHA supplementation have generally been of short durations with small numbers of subjects or other design limitations. The present study employed 176 healthy subjects (mixed genders, ages 18-45 years) who were subjected to cognitive performance testing at initiation of the trial and at the end (6 months later). The testing included evaluations of ‘episodic memory’ (immediate and delayed word recall, delayed word recognition, and delayed picture recognition) as well as ‘working memory’. One group (85 subjects) received daily supplementation with 1,160 mg DHA (plus 170 mg EPA) while the control group (91 subjects) received daily placebo supplementation (lacking DHA/EPA). Blood measures of omega-3 were also conducted.
As expected, a marked increase in the levels of DHA and EPA was found after 6 months in the red blood cells of the group receiving omega-3 supplementation but not in the controls (receiving the placebo). Interestingly, the reaction time (RT) for episodic memory improved significantly in the DHA-supplemented group with these subjects responding faster to the tasks than the controls. The improvement in episodic memory as seen in the women who consumed DHA (as compared to those on placebo) equated to correctly remembering or recognizing approx. one more word or picture. The significant improvement in working memory as seen in the men with DHA equated with them completing the working memory task faster by 223 mseconds (20 %) relative to men on placebo. The authors concluded that ‘young healthy adults may cognitively benefit from an increased consumption of DHA’.
Dr. Holub's Comments:
The present study raises a number of interesting perspectives and questions. Firstly, it supports the somewhat limited body of published clinical trials on the cognitive benefits that may result from improving long-chain omega-3 fatty acid intakes in healthy young adults. Many more evaluations in this area have been conducted on infants from mothers (pregnant and/or lactating) who consumed different levels of DHA/EPA or on term infants given formula without or with DHA. Secondly, the benefits of DHA/EPA supplementation on the cognitive parameters measured in this trial were observed in subjects with very low intakes (averaging below 30 mg of DHA plus EPA daily). Such intakes are below typical daily intakes in New Zealand, Australia, North America , many other countries of 100-150 mg/person/day. While rarely addressed in the field of omega-3 clinical trials, one wonders if beneficial effects of DHA/EPA on cognitive, visual, and other health benefits may be recorded more often and more dramatically in subjects who are much more deprived in their habitual intakes of long-chain omega-3 fatty acids relative to the general population. While the cognitive benefits DHA/EPA supplementation reported in the present study were attributed to DHA, it is possible that the concomitant intake of EPA (170 mg/person/day) may have contributed somewhat to the overall findings even though DHA concentrations in the brain greatly predominant over the very minor levels of EPA. In this regard, recent studies in rodents (by Dr. R. Bazinet and colleagues at the Univ. of Toronto) have shown that EPA is taken up readily into the brain and that EPA , while not accumulating in neuronal membrane phospholipids as does DHA, is rapidly metabolized to products which may be of functional importance.