Brain Fats – Seafood, Omega-3 PUFAs, Phospholipids and Vitamin D
Brain Fats – Seafood, Omega-3 PUFAs, Phospholipids and Vitamin D
The omega-3 fat, docosahexaenoic acid (DHA) is the most abundant PUFA in the brain, concentrated in the grey matter and, particularly at the synapses.1 DHA is incorporated into membrane phospholipids, where it affects the properties of the membrane, for example, maintaining membrane fluidity. DHA, along with other omega-3 fats EPA, DPAn-3 and their mediators are involved in a wide variety of processes in the brain, such as making new neurons, synaptic connections and the regulation of inflammation.2
Fish, especially cold-water oily fish, contain high levels of DHA and EPA, and epidemiological studies consistently suggest that an elevated fish intake is associated with decreased risk of neurodegenerative diseases, such as Alzheimer’s disease.3 Recent estimates suggest that worldwide many populations are currently consuming DHA and EPA at levels well below the recommendations issued by many international authorities (GOED), with and blood levels of EPA and DHA have been estimated to be low to very low for most of the world, which may increase global risk for chronic disease.4
Interestingly, positive associations have also been found between walnut consumption and cognitive performance.5 Walnuts are a source of omega-3 fat, alpha-linolenic acid (ALA) and also a range of antioxidants.
Omega-3 Supplementation and cognitive decline
DHA supplementation appears to show the greatest promise in the early stage before the onset of memory loss symptoms,1 and at levels at or above 1000 mg per day (Ismail 2015).6
A study of healthy 50-75 year olds were given 2,200 mg a day of omega 3 fish oils for six months not only reported significant increase in executive function, one aspect of cognition that is a hallmark of Alzheimer’s, but also beneficial structural changes in white matter integrity and grey matter volume in the brain. The cognitive improvement correlated with blood levels of omega-3 PUFAs.7
A randomized, double-blind, placebo-controlled, clinical study, gave 900 mg of DHA a day for 24 weeks and reported an improvement in learning and memory function in those with age-related cognitive decline.8 In a further trial by the same research group, giving 2,000 mg a day of DHA or placebo to 402 people with mild to moderate Alzheimer’s disease, therefore further along the disease process, for a period of 18 months found no cognitive improvement.9
Phospholipids, rich in eggs and seafood, are abundant in the brain. They make up the membranes of the different types of cells in the brain. These include Phosphatidylethanolamine (PE) and phosphatidylserine (PS) phosphatidylcholine (PC) and phosphatidylinositol (PI). They become attached to omega-3 DHA. (see film ‘Build Your Brain‘) Phosphatidylethanolamine (PE) and phosphatidylserine (PS) are enriched in DHA, whereas much lower levels are found in phosphatidylcholine (PC) and phosphatidylinositol (PI).3 Attaching DHA to phospholipids is a process that requires methylation, which is dependent on B vitamins.9 Interestingly, although DHA is typically found high in PS, levels have been found to be low in PS in post-mortem samples from Alzheimer’s disease patients.10 PS supplementation may benefit cognition in the elderly,11 but as PS is highly enriched with DHA, it is currently unclear whether the potential beneficial effects of PS on cognition are due to the intact PS or DHA. Although PC is not highly enriched in DHA, higher plasma concentrations of PC-DHA are associated with reduced risk of dementia and AD,12 and post mortem samples from AD shows depletion of PC-DHA in grey matter.13
A number of trials have investigated the effects of providing multinutrient supplements containing a range of nutritional factors with the aim of supporting phospholipid biosynthesis. Our recent systematic review identified that omega-3 PUFAs and B vitamins as part of these multinutrient formulas confers benefits on cognition in older adults across a range of different types of measures of cognition in older adults.14 Furthermore, 12-week trial of citicoline has shown cognitive benefits in healthy older adults.15
The primary source of vitamin D is exposure to sunlight. Seafood provides the most dietary vitamin D. Vitamin D deficiency increases risk of AD.161,17,18 Supplements of vitamin D can be derived from animal or fungal sources (mushrooms and yeast). Supplementing 800iu (20mg) a day for 12 months has been shown to improve cognitive function and lessen amyloid protein markers.19
In a study in France involving 912 elderly patients followed for twelve years, a total of 177 dementia cases (124 AD) occurred: 25(OH)D deficiency was associated with a nearly three-fold increased risk of AD.20
1.Dyall, S. C. (2015, 2015-April-21). Long-chain omega-3 fatty acids and the brain: A review of the independent and shared effects of EPA, DPA and DHA [Review]. Frontiers in Aging Neuroscience, 7(52). https://doi.org/10.3389/fnagi.2015.00052
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