Fish and Their Oils: Associated With Cognitive Protection

nutrition diet healthFish oils are a source of the long chain fatty acids docosahexaenoic acid (DHA, C22:6 (n-3)) and eicosapentaenoic acid (EPA, C20:5 (n-3)). These oils are important in human health because they can feed into the essential fatty acid pathways and provide a source of important eicosanoid hormones. The production of eicosanoids allows cell regulation to proceed through complex intracellular messaging systems, and this classical pathway is particularly important for regulating cellular inflammation. This explains the anti-inflammatory effects of consuming fatty fish and their oils. However, a non-classical pathway also exists, and in this pathway a series of docosanoids can be produced from DHA. This non-classical pathway may be a key regulator of neuronal health and may provide significant anti-inflammatory effects to neurones. This may explain the reported effects of DHA on neuronal and brain development in foetuses and infants during growth, as well as the cognitive benefits to adults.

fish oils DHA EPA

Docosahexaenoic acid (DHA) has a number of health effects. Classically it is converted to eicosapentaenoic acid (EPA), and this then is subsequently converted to a number of eicosanoids, short lived hormones that regulate cellular function. However a non-classical pathway for the conversion of docosahexaenoic acid to a number of neuroprotective docosanoids, exists. This may explain the association between fish oil consumption and protection from neurodegenerative disease. A group of compounds called the resolvins can also be synthesised from both docosahexaenoic acid and eicosapentaenoic acid. These may also have anti-inflammatory effects.

A number of studies have investigated the associations between fish oil consumption and protection from neuronal degenerative disease. In a recent study, researchers analysed the data to date regarding the protective effects of fish and fish oil on the main neurodegenerative diseases. The data they collated came from 21 studies that involved over 180,000 individuals. The results of this data analysis showed that a 1 serving increase in fish per week was associated with a significant reduction in the risk of dementia and Alzheimer’s disease. Additionally, a 100 mg per day increase in the intake of DHA was associated with a significantly lower risk of dementia and Alzheimer’s disease. The current recommendation is to consume more fatty fish in the diet because of the beneficial health effects this confers. These health effects appear to be in part due to a decrease in the rate of neurodegeneration during ageing or disease. Supplements of fish oils and algal oils are also likely effective in this regard.

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Zhang, Y., Chen, J., Qiu, J., Li, Y., Wang, J. and Jiao, J. 2016. Intakes of fish and polyunsaturated fatty acids and mild-to-severe cognitive impairment risks: a dose-response meta-analysis of 21 cohort studies. American Journal of Clinical Nutrition. 103: 330-340

About Robert Barrington

Robert Barrington is a writer, nutritionist, lecturer and philosopher.
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