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
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
Supplementation
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
Vitamin D
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
References
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
2. Dyall, S. C., Balas, L., Bazan, N. G., Brenna, J. T., Chiang, N., da Costa Souza, F., Dalli, J., Durand, T., Galano, J. M., Lein, P. J., Serhan, C. N., & Taha, A. Y. (2022, Apr). Polyunsaturated fatty acids and fatty acid-derived lipid mediators: Recent advances in the understanding of their biosynthesis, structures, and functions. Prog Lipid Res, 86, 101165. https://doi.org/10.1016/j.plipres.2022.101165
3. Dyall SC, Michael-Titus AT. Neurological benefits of omega-3 fatty acids. Neuromolecular Med. 2008;10(4):219-35. doi: 10.1007/s12017-008-8036-z. Epub 2008 Jun 10. PMID: 18543124.
4. Stark, K. D., Van Elswyk, M. E., Higgins, M. R., Weatherford, C. A., & Salem, N., Jr. (2016, Jul). Global survey of the omega-3 fatty acids, docosahexaenoic acid and eicosapentaenoic acid in the blood stream of healthy adults. Prog Lipid Res, 63, 132-152. https://doi.org/S0163-7827(15)30033-3 [pii]10.1016/j.plipres.2016.05.001 Alzheimers Dement. 2017 Nov;13(11):1207-1216. doi: 10.1016/j.jalz.2017.03.003. Epub 2017 May 16
5. Theodore LE, Kellow NJ, McNeil EA, Close EO, Coad EG, Cardoso BR. Nut Consumption for Cognitive Performance: A Systematic Review. Adv Nutr. 2021 Jun 1;12(3):777-792. doi: 10.1093/advances/nmaa153. PMID: 33330927; PMCID: PMC8166568.
6. Ismail
7. A. Veronica Witte, Lucia Kerti, Henrike M. Hermannstädter, Jochen B. Fiebach, Stephan J. Schreiber, Jan Philipp Schuchardt, Andreas Hahn, Agnes Flöel, Long-Chain Omega-3 Fatty Acids Improve Brain Function and Structure in Older Adults, Cerebral Cortex, Volume 24, Issue 11, November 2014, Pages 3059–3068, https://doi.org/10.1093/cercor/bht163
8. Yurko-Mauro K, McCarthy D, Rom D, et al; Beneficial effects of docosahexaenoic acid on cognition in age-related cognitive decline. Alzheimers Dement. 2010; 6, 456-64
9. Quinn JF, Raman R, Thomas RG, et al; Docosahexaenoic acid supplementation and cognitive decline in Alzheimer disease: a randomized trial. JAMA, 2010; Nov 3;304(17):1903-11.
10. A David Smith, Fredrik Jernerén, Helga Refsum, ω-3 fatty acids and their interactions, The American Journal of Clinical Nutrition, Volume 113, Issue 4, April 2021, Pages 775–778, https://doi.org/10.1093/ajcn/nqab013
11. Cunnane, Stephen & Schneider, Julie & Tangney, Christine & Tremblay-Mercier, Jennifer & Fortier, Mélanie & Bennett, David & Morris, Martha. (2012). Plasma and Brain Fatty Acid Profiles in Mild Cognitive Impairment and Alzheimer’s Disease. Journal of Alzheimer’s disease : JAD. 29. 691-7. 10.3233/JAD-2012-110629.
12. Richter Y, Herzog Y, Lifshitz Y, Hayun R, Zchut S. The effect of soybean-derived phosphatidylserine on cognitive performance in elderly with subjective memory complaints: a pilot study. Clin Interv Aging. 2013;8:557-63. doi: 10.2147/CIA.S40348. Epub 2013 May 21. PMID: 23723695; PMCID: PMC3665496.
13. Schaefer EJ, Bongard V, Beiser AS, Lamon-Fava S, Robins SJ, Au R, Tucker KL, Kyle DJ, Wilson PW, Wolf PA. Plasma phosphatidylcholine docosahexaenoic acid content and risk of dementia and Alzheimer disease: the Framingham Heart Study. Arch Neurol. 2006 Nov;63(11):1545-50. doi: 10.1001/archneur.63.11.1545. PMID: 17101822.
14. Yuki D, Sugiura Y, Zaima N, Akatsu H, Takei S, Yao I, Maesako M, Kinoshita A, Yamamoto T, Kon R, Sugiyama K, Setou M. DHA-PC and PSD-95 decrease after loss of synaptophysin and before neuronal loss in patients with Alzheimer’s disease. Sci Rep. 2014 Nov 20;4:7130. doi: 10.1038/srep07130. PMID: 25410733; PMCID: PMC5382699.
15. Fairbairn, P., Dyall, S. C., & Tsofliou, F. (2022, Apr 27). The Effects of Multi-Nutrient Formulas containing a Combination of Omega-3 Polyunsaturated Fatty Acids and B vitamins on Cognition in the older adult: A Systematic Review and Meta-analysis. Br J Nutr, 1-42. https://doi.org/10.1017/S0007114522001283
16. Nakazaki E, Mah E, Sanoshy K, Citrolo D, Watanabe F. Citicoline and Memory Function in Healthy Older Adults: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial. J Nutr. 2021 Aug 7;151(8):2153-2160. doi: 10.1093/jn/nxab119. PMID: 33978188; PMCID: PMC8349115.
17. Sommer I, Griebler U, Kien C, Auer S, Klerings I, Hammer R, Holzer P, Gartlehner G. Vitamin D deficiency as a risk factor for dementia: a systematic review and meta-analysis. BMC Geriatr. 2017 Jan 13;17(1):16. doi: 10.1186/s12877-016-0405-0. PMID: 28086755; PMCID: PMC5237198;
18. Jayedi A, Rashidy-Pour A, Shab-Bidar S. Vitamin D status and risk of dementia and Alzheimer’s disease: A meta-analysis of dose-response †. Nutr Neurosci. 2019 Nov;22(11):750-759. doi: 10.1080/1028415X.2018.1436639. Epub 2018 Feb 15. PMID: 29447107;
19. Chai B, Gao F, Wu R, Dong T, Gu C, Lin Q, Zhang Y. Vitamin D deficiency as a risk factor for dementia and Alzheimer’s disease: an updated meta-analysis. BMC Neurol. 2019 Nov 13;19(1):284. doi: 10.1186/s12883-019-1500-6. PMID: 31722673; PMCID: PMC6854782.
20. Jia J, Hu J, Huo X, Miao R, Zhang Y, Ma F. Effects of vitamin D supplementation on cognitive function and blood Aβ-related biomarkers in older adults with Alzheimer’s disease: a randomised, double-blind, placebo-controlled trial. J Neurol Neurosurg Psychiatry. 2019 Dec;90(12):1347-1352. doi: 10.1136/jnnp-2018-320199. Epub 2019 Jul 11. PMID: 31296588.
21. Feart C, Helmer C, Merle B, Herrmann FR, Annweiler C, Dartigues JF, Delcourt C, Samieri C. Associations of lower vitamin D concentrations with cognitive decline and long-term risk of dementia and Alzheimer’s disease in older adults. Alzheimers Dement. 2017 Nov;13(11):1207-1216. doi: 10.1016/j.jalz.2017.03.003. Epub 2017 May 16. PMID: 28522216.
