A recent study on the eating habits of Australians found that only 20 percent consume the recommended daily intake of omega-3 polyunsaturated fatty acids (PUFA).¹ 

This reduced intake of omega-3 PUFA is thought to be associated with increased inflammatory processes, reduced cardiovascular health and compromised cognitive function in later life.^2-4

A rich source of these omega-3 PUFA is fresh fish and fish oil supplements which also contain eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and have been associated with an array of health benefits.^4-7  Omega-3 fatty acids are utilised by various parts of the body, including cell membranes, the development of the central nervous system, frontal cortex function, synaptic membrane proteins and play a significant role in reducing inflammatory cytokines.^4-7

Cognition and Aging

Cognitive decline is a well-documented occurrence with aging and is thought to be caused by structural changes in the brain.⁸ Clinical studies suggest that multiple biological, behavioural, social, and environmental factors may contribute to the risk for cognitive decline.⁸

Structural brain changes contributing to cognitive decline can include:

• Disruptions in mitochondrial function leading to overproduction of reactive oxygen species.⁹
• Increased oxidative stress which can contribute damage to membrane lipids, proteins and DNA, resulting in elevated inflammatory cytokines.⁹
• Compromised membrane fluidity due to increased presence of cholesterol, reduced activity of desaturase enzymes, blockages to phospholipid pathways and increased oxidative stress.¹⁰
• DNA damage caused by increased oxidative stress, leading to genomic instability and cellular dysfunction.¹¹
• Alterations in energy metabolism due to compromised mitochondrial function causing a reduction in ATP required for optimal cognitive function.^8-11

Factors Associated with Cognitive Decline

• Increased consumption of saturated and trans fatty acids ^2,3
• Genetic Factors¹²
• Aging¹²
• Diabetes¹²
• Depression¹²
• Smoking¹²

Ongoing research continues to study the effects of fish oil supplementation in improving cognitive performance, especially in aging people who have an increased risk of cognitive decline, dementia and Alzheimer disease; with research showing the use of long term fish oil supplementation to be associated with less cerebral cortex grey matter and hippocampal atrophy resulting in better performance on cognitive tests, compared with nonusers.⁶

A prospective follow-up study of 899 patients who were free from dementia and had a median age of 76 years were followed up for an average of 9 years to track for the development of all-cause dementia and Alzheimer disease. Subjects with baseline plasma phosphatidylcholine DHA levels in the upper quartile experienced a significant 47% lower risk of dementia compared with participants with levels in the lower 3 quartiles (Figure 1). Subjects in the upper quartile had a mean DHA intake of 180 mg/d and an average fish intake of 3.0 servings per week.¹³

Figure One: Incidence of dementia in subjects with baseline plasma phosphatidylcholine DHA levels in the upper quartile compared with those with levels in the lower 3 quartiles.

While raised plasma DHA levels have shown to reduce incidence of dementia it is important to know how much DHA needs to be consumed each day to improve cognitive function. In a recent meta-analysis, research found DHA intake above 580 mg/day significantly improved episodic memory in subjects with mild memory complaints. Regardless of cognitive status, combined DHA/EPA supplementation of > 1 g/day was found to improve episodic memory in subjects 45 years or older.¹⁴

Conclusion

Cognitive decline in aging is a well-documented occurrence and can be associated with an increased risk of dementia and Alzheimer disease. Additional factors such as, increased consumption of saturated and trans fatty acids and genetic factors, have shown to contribute to cognitive decline and other cognitive problems such as dementia.

In aging clients with a family history of cognitive diseases or those suffering from mild memory complaints, fish oil supplementation consisting of at least 580mg/day of DHA in addition to the introduction of more fresh fish into the diet and reduced intake of saturated and trans fatty acids, may be an effective strategy in supporting cognitive health and reducing the speed of cognitive decline in these patients.

References

1. Meyer BJ. Australians are not Meeting the Recommended Intakes for Omega-3 Long Chain Polyunsaturated Fatty Acids: Results of an Analysis from the 2011-2012 National Nutrition and Physical Activity Survey. Nutrients. 2016;8(3):111, 10.3390/nu8030111.
2. Morris MC, Tangney CC. Dietary fat composition and dementia risk. Neurobiol Aging. 2014;35 Suppl 2:S59-64, 10.1016/j.neurobiolaging.2014.03.038.
3. Barnard ND, Bunner AE, Agarwal U. Saturated and trans fats and dementia: a systematic review. Neurobiol Aging. 2014;35 Suppl 2:S65-73, 10.1016/j.neurobiolaging.2014.02.030.
4. Swanson D, Block R, Mousa SA. Omega-3 fatty acids EPA and DHA: health benefits throughout life. Adv Nutr. 2012;3(1):1-7, 10.3945/an.111.000893.
5. Witte AV, Kerti L, Hermannstadter HM, Fiebach JB, Schreiber SJ, Schuchardt JP, et al. Long-chain omega-3 fatty acids improve brain function and structure in older adults. Cereb Cortex. 2014;24(11):3059-68, 10.1093/cercor/bht163.
6. Daiello LA, Gongvatana A, Dunsiger S, Cohen RA, Ott BR, Alzheimer's Disease Neuroimaging I. Association of fish oil supplement use with preservation of brain volume and cognitive function. Alzheimers Dement. 2015;11(2):226-35, 10.1016/j.jalz.2014.02.005.
7. Ramakrishnan U, Gonzalez-Casanova I, Schnaas L, DiGirolamo A, Quezada AD, Pallo BC, et al. Prenatal supplementation with DHA improves attention at 5 y of age: a randomized controlled trial. Am J Clin Nutr. 2016;104(4):1075-82, 10.3945/ajcn.114.101071.
8. Haast RA, Kiliaan AJ. Impact of fatty acids on brain circulation, structure and function. Prostaglandins Leukot Essent Fatty Acids. 2015;92:3-14, 10.1016/j.plefa.2014.01.002.
9. Perluigi M, Swomley AM, Butterfield DA. Redox proteomics and the dynamic molecular landscape of the aging brain. Ageing Res Rev. 2014;13:75-89, 10.1016/j.arr.2013.12.005.
10. Sinn N, Milte CM, Street SJ, Buckley JD, Coates AM, Petkov J, et al. Effects of n-3 fatty acids, EPA v. DHA, on depressive symptoms, quality of life, memory and executive function in older adults with mild cognitive impairment: a 6-month randomised controlled trial. Br J Nutr. 2012;107(11):1682-93, 10.1017/S0007114511004788.
11. Canugovi C, Misiak M, Ferrarelli LK, Croteau DL, Bohr VA. The role of DNA repair in brain related disease pathology. DNA Repair (Amst). 2013;12(8):578-87, 10.1016/j.dnarep.2013.04.010.
12. Plassman BL, Williams JW, Burke JR, Holsinger T, Benjamin S. Systematic review: factors associated with risk for and possible prevention of cognitive decline in later life. Annals of Internal Medicine. 2010;153(3):182-93,
13. Schaefer EJ, Bongard V, Beiser AS, Lamon-Fava S, Robins SJ, Au R, et al. Plasma phosphatidylcholine docosahexaenoic acid content and risk of dementia and Alzheimer disease: the Framingham Heart Study. Archives of neurology. 2006;63(11):1545-50,
14. Yurko-Mauro K, Alexander DD, Van Elswyk ME. Docosahexaenoic acid and adult memory: a systematic review and meta-analysis. PLoS One. 2015;10(3):e0120391, 10.1371/journal.pone.0120391.