Can We Really Do Something To Slow Down The Mental Decline That Is Assumed To Be A Normal Part of Ageing?
"You're never too old to become younger!" Mae West
I've dealt with this topic at length inThe Brain Food Diet, so it would be pointless to go over the ground in detail here. But perhaps it is appropriate for me to make a few relevant comments as well as to increase the sources for further reading, expecially for professional visitors.
How convinced am I that the omega-3s, and DHA in particular, really do slow down or even prevent the cognitive decline we assume to be a normal part of ageing? Until two years or so ago, I hadn't fully made up my mind. Some studies appeared to point strongly in this direction but they were contradicted by one or two studies that appeared to show the very opposite. The contradictory studies were fewer and appeared to point in bizarre directions, such as consumption of saturated fat was good for brain function. I'm afraid the evidence against that is so strong it made such claims suspect to me.
In the last two years, and in most tellingly in 2007, a series of high quality studies convinced me beyond all reasonable doubt. You will find those studies outlined in The Brain Food Diet.
What about the dose-benefit effect of omega-3s, and DHA in particular, shown in the most recent studies?
I have to admit that this was one of the key factors in the new studies that helped me make up my mind. Dose-benefit effect is a well-known and highly-regarded observation in medical and pharmacological studies.
It is important to grasp that maximum benefit is likely to come from taking omega-3s, and DHA in particular, long before cognitive decline sets in. Many doctors, such as myself, suspect that cognitive decline (and Alzheimer's disease) begins long before it become clinically manifest, perhaps as early as the forties -- and certainly by the fifties. Whether you take your omega-3s as oily fish in your diet, or as fish oil or omega-3 supplements, you shouldn't regard yourself as taking a drug-style of treatment, but rather that you are restoring the nutritional balance of your diet to normal.
What about taking omega-3s as treatment in people who, tragically, have already developed symptoms of cognitive decline?
Yes! I would strongly sanction this - and for a number of reasons. Cognitive decline, like vascular dementia, is widely seen among the press and even among doctors as an area that has not had its fair share of attention and resources. Often, and especially if the sufferer is in the older age group, little precise investigation is performed. In consequence, people with recurrent small strokes will be included in broad umbrella group that will also include many who have a more subtle explanation for their symptoms, such as vitamin or essential fatty acid deficiency. Omega-3s would help both those suffering from recurrent small strokes as well as those suffering from essential omega-3 deficiency. So - always with the proviso you are not already on aspirin or anticoagulant drugs - patients would have nothing to lose and potentially a lot to gain from taking the recommended omega-3s.
Further Reading
Akbar M, Calderon F, et al (2005). Docosahexaenoic acid: a positive modulator of Akt signaling in neuronal survival. PNAS 102(31):10858-63.
Beydoun MA, Kaufman JS, et al (2007). Plasma n-3 fatty acids and the risk of cognitive decline in older adults: the atherosclerosis risk in communities study. Am J Clin Nutr 85: 1103-11.
Boukje MvG, Tijhuis M, et al (2007). Fish consumption, n-3 fatty acids, and subsequent 5-y cognitive decline in elderly men: the Zutphen Elderly Study. Am J Clin Nutr 85: 1142-47.
Connor WE, Neuringer M and Lin DS (1990). Dietary effects on brain fatty acid composition: the reversibility of n-3 fatty acid deficiency and turnover of docosohexanoic acid in the brain, erythrocytes, and plasma of rhesus monkeys. J of Lipid Research 31: 237-47.
Connor WE (2000). Importance of n-3 fatty acids in health and disease. Am J Clin Nutr 71(suppl): 171S-75S.
Conquer JA, Tierney MC, et al (2000). Fatty acid analysis of blood plasma in patients with Alzheimer's disease, other types of dementia, and cognitive impairment. LIPIDS 35:1305-21.
Crawford MA, Bloom M, et al (1999). Evidence for the unique function of docosahexaenoic acid during the evolution of the modern hominid brain. Lipids 34(S): 539-47.
Gamoh S, Hashimoto M, et al (2001). Chronic administration of docosahexaenoic acid improves the performance of radial arm maze task in aged rats. Clin Exp Pharmacol Physiol 28(4):266-70.
Gelder BM van, Tijhuis M, et al (2007). Fish consumption, n-3 fatty acids, and subsequent 5-y cognitive decline in elderly men: the Zutphen Elderly Study. Am J Clin Nutr 85: 1142-7.
Gerster H (1998). Can adults adequately convert alpha-linolenic acid (18:3n-3) to eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3)? Int J Vitam Nutr Res 68:159-73.
Greiner RS, Moriguchi T, et al (1999). Rats with low levels of brain docosahexaenoic acid show impaired performance in olfactory-based and spatial learning tasks. Lipids 34 Suppl S239-43.
Hashimoto M, Tanabe Y, et al (2005). Chronic administration of docosahexaenoic acid ameliorates the impairment of spatial cognition learning ability in amyloid β-infused rats. J Nutr 135: 549-55.
He K, Rimm EB, et al (2002). Fish consumption and risk of stroke in men. JAMA 288: 3130-6.
Heude B, Ducimetiere P, et al (2003). Cognitive decline and fatty acid composition of erythrocyte membranes – the EVA study. Am J Clin Nutr 77: 803-08.
Iso H, Rextrode KM, et al (2001). Intake of fish and omega-3 fatty acids and risk of stroke in women JAMA 285: 304-12.
Kang JH, Cook N, et al (2007). Low dose aspirin and cognitive function in the women’s health study cognitive cohort. BMJ 334: 987-89.
Kalmijn S, Feskens EJM, et al (1997). Polyunsaturated fatty acids, antioxidants, and cognitive function in very old men. Am J Epidemiol 145(1): 33-41.
Laurin D, Verreault R, et al (2003). Omega-3 fatty acids and risk of cognitive impairment and dementia. J of Alzheimer’s Disease 5: 315-22.
Laurin D, Verreault R, et al (2001). Physical activity and risk of cognitive impairment and dementia in elderly persons. Arch Neurol 58: 498-504.
Lauritzen I, Blondeau N, et al (2000). Polyunsaturated fatty acids are potent neuroprotectors. EMBO J 19:1784-1793.
Lauritzen L, Hansen HS, et al (2001). The essentiality of long-chain n-3 fatty acids in relation to development and function of the brain and retina. Prog Lipid Res 40:1-94.
Lim SY and Suzuki H (2000). Intakes of dietary docosahexaenoic acid ethyl ester and egg phosphatidylcholine improve maze-learning ability in young and old mice. J Nutr 130(6):1629-32.
Lim S, and Suzuki H (2001). Changes in maze behavior of mice occur after sufficient accumulation of docosahexaenoic acid in brain. J Nutr 131(2):319-24.
McCann JC and
Minami M, Kimura S, et al (1997). Dietary docosahexaenoic acid increases cerebral acetylcholine levels and improves passive avoidance performance in stroke-prone spontaneously hypertensive rats. Pharmacol Biochem Behav 58(4):1123-9.
Morris MC, Evans DA, et al (2005). Fish consumption and cognitive decline with age in a large community study. Arch Neurol 62: 1-5.
Rextrode IH, Stampfer MJ, et al (2001). Intake of fish and omega-3 fatty acids and risk of stroke in women. JAMA 285: 304-12.
Simopolous AP, Leaf A and
Small SA (2001). Age-related memory decline. Arch Neurol 58:360-4.
Suzuki H, Hayakawa S and Wada S (1989). Effect of age on the modification of brain polyunsaturated fatty acids and enzyme activities by fish oil diet in rats. Mech Aging Devel 50:17-25.
Whalley LJ, Cox HC et al (2004). Cognitive ageing, childhood intelligence, and the use of food supplements: possible involvement of n-3 fatty acids. Am J Clin Nutr 80: 1650-7.
Yehuda S, Rabinovitz S, et al (2002). The role of polyunsaturated fatty acids in restoring the aging neuronal membrane. Neurobiol. Aging 23: 843-853.
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