Omega-3 Fatty Acids, Brain Volume and Executive Function
“A study of older adults at risk of late-onset Alzheimer’s disease found that those who consumed more omega-3 fatty acids did better than their peers on tests of cognitive flexibility – the ability to efficiently switch between tasks – and had a bigger anterior cingulate cortex, a brain region known to contribute to cognitive flexibility.” A direct quote from News-Medical.net.
Zamroziewicz and colleagues studied 95 elderly adults (68y, 72% female) without diagnosis of cognitive impairment, dementia, stroke, cancer or psychiatric illness. The scientists hypothesized that genetic polymorphisms in APOE, namely APOE e4 allele, might be at higher risk of cognitive decline. Fasting plasma fatty acids, executive function (by Delis-Kaplan Executive Function System Trail Making Test), and brain volume were measured.
The APOE e4 hypothesis was not validated; probably because of the relatively few people studied.
Average omega-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) were 102 and 216 nmol/mL in the low and high groups. Higher concentrations of omega-3s in the blood were correlated with brain size and cognitive flexibility.
According to nationally-representative, cross-sectional data (CDC Second Nutrition Report), the omega-3 fatty acid concentrations of adult Americans (>20y) range between 289 to 321 nmol/mL (lower and upper 95% CI). This equates to an omega-3 index of approximately 2. Clearly, the much n-3 LCPUFA concentrations of the elderly subjects studied by Zamroziewicz indicates they did not consume much fatty fish or other sources of omega-3s.
In the Nurses’ Health Study, the average plasma omega-3 index was 2.49%. Virtanen and colleagues reported a mean n-3 LCPUFA concentration (omega-3 index) of 4.67% at baseline. Blood omega-3 concentrations were inversely associated with blood pressure.
One of the most powerful statements in the paper by Zamroziewicz et al (2015) is in the last paragraph: “The strength of this study includes the use of blood biomarkers to measure nutrition, which provided a more reliable assessment of dietary intake than that of food frequency questionnaires.”
Zamroziewicz MK, Paul EJ, Rubin RD, Barbey AK. Anterior cingulate cortex mediates the relationship between O3PUFAs and executive functions in APOE e4 carriers. 2015 Front Aging Neurosci doi: 10.3889/10.3389/fnagi.2015.00087
Sun Q, Ma J, Campos H, Hankinson SE, Hu FB. Comparison between plasma and erythrocyte fatty acid content as biomarkers of fatty acid intake in us women. 2007 Am J Clin Nutr 7, 86, 74-81
Virtanen JK, Nyantika AN, Kauhanen J, Voutilainen S, Tuomainen TP. Serum long-chain n-3 polyunsaturated fatty acids, methylmercury and blood pressure in an older population. 2012 Hypertens Res doi: 10.1038/hr.2012.80