Associations between omega-3 PUFA concentrations and cognitive function after recovery from late-life depression
– Source: American Journal of Clinical Nutrition, Feb 2012
By CC Chiu, et al.
[Note: Though omega-3 PUFAs can be derived from animal sources, especially fish and krill oils, the omega-3 food chain originates in plants – e.g., seaweed & algae eaten by krill and fish. The omega-3s in fish oil and krill oil are called eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The omega-3 found in plant sources such as flaxseed is called alpha-linolenic acid (ALA). The red blood cells of the subjects in this study were tested for all of these.]
Background: Lower concentrations of n-3 PUFAs [omega-3 polyunsaturated fatty acids]:
• Have been reported to be associated with cognitive impairment and dementia,
• But also with depression - itself a potential risk factor for cognitive decline.
Objective: The aims of this study were to investigate associations between n-3 PUFA concentrations in erythrocyte [red blood cell] membrane or plasma [liquid in which blood cells are suspended] and cognitive function in an at-risk sample of older people with previous major depression, and to explore specificity with respect to cognitive domains.
• A cross-sectional sample of 132 eligible participants who had recovered from major depression (mean +/- SD age: 67.8 plus/minus 6.6 years) were enrolled from outpatient psychiatric services.
• A series of cognitive tests and a structured questionnaire were administered.
• Fasting blood samples were collected for n-3 PUFA measurements.
Results: Higher EPA and total n-3 PUFA concentrations and a lower ratio of arachidonic acid-to-EPA in erythrocyte membranes were associated with a higher cognitive composite score: independent of age and sex, but no longer significant after adjustment for education. No associations were found with plasma concentrations of any fatty acid. [Arachidonic acid is a type of omega-6 PUFA most plentiful in red meats that is essential for growth of skeletal muscle but considered harmful when in a higher ratio vs. omega-3s.]
Considering individual cognitive tests the strongest and most consistent correlations were found between immediate recall and concentrations of total n-3 PUFAs and alpha-linolenic acid (ALA) in erythrocytes, which were observed only in participants with recurrent depression.
• Total erythrocyte n-3 PUFA concentrations are positively associated with cognitive function, particularly immediate recall, in older people with previous depression. [Higher levels, better cognitive function & immediate recall, and vice-versa.]
• Lower concentrations of n-3 PUFAs or ALA in erythrocyte membranes may be good predictors for cognitive impairment in older people with previous recurrent depression.
Source: American Journal of Clinical Nutrition, Feb 2012;95(2):420-407. PMID: 22218153, by Chiu CC, Frangou S, Chang CJ, Chiu WC, Liu HC, Sun IW, Liu SI, Lu ML, Chen CH, Huang SY, Dewey ME, Stewart R. Department of Psychiatry, Taipei City Psychiatric Center, Taipei City Hospital, Taiwan.