Our brains are made of fat – about 50%, in fact. At least one third of the brain’s fat is made from essential polyunsaturated fats (PUFAs) that must be obtained from the diet.
PUFAs that are important to brain health include arachidonic acid (AA), docosahexaenoic acid (DHA) which make up 50% and 40% of brain PUFAs, respectively and eicosapentaenoic acid (EPA) which represents <10%.(1)
AA is derived from Omega 6 fatty acids and found in vegetable seed oils such as corn, safflower, soybean and cottonseed. DHA and EPA are derived from Omega 3 fatty acids found in fish especially salmon, leafy greens, walnuts and seeds such as chia, hemp and flax.
The conversion of O6 and O3 essential fats into their respective longer chain derivatives is inefficient in the body and therefore it is recommended to supplement with DHA and EPA directly since these are more likely to be deficient in the modern diet.(1,2,3)
Omega 6 (O6) and Omega 3 (O3) acids oppose each other and are sometimes referred to as pro-inflammatory and anti-inflammatory respectively. A little bit of inflammation is good like the kind that tells your body to heal itself when you stub your toe. However, a lot of inflammation is not good for systemic health maintenance and is now known to be the root cause of many chronic disease conditions e.g. heart disease, diabetes and even cancer.
Inflammation is the root cause of all chronic disease in the body.
The modern diet is heavily weighted towards Omega 6 fatty acids and the ratio of O6 to O3 can be as high as 25:1 whereas it is believed that a ratio closer to or lower than 4:1 is better for sustained health.(3,4) One reason for this imbalance is the dramatic rise in the consumption of vegetable oils following the official dietary guidelines advising us to eat less saturated fat and cholesterol over the past few decades.(5) An overconsumption of O6 PUFAs can compete with and lower the conversion of vital neuroprotective O3’s.(1)
Brain protective effects of Omega 3 fats
Both AA and DHA are critical for brain development and maintenance of brain structure and function. DHA is particularly important for developing neurons and signaling between brain cells with implications for cognition and behavior. EPA has shown to be helpful in the treatment for depression and a deficiency has been implicated in substance abuse disorders.(1) Low DHA and EPA levels are also associated with lower dopamine levels – the neurotransmitter responsible for pleasure and implicated in clinical depression.(6) Studies of depressed individuals have shown a lower ratio of DHA and EPA to other PUFAs in the brain and supplements with EPA have shown to relieve symptoms.(1)
Scientists from USDA Human Nutrition Research Center on Aging (USDA HNRCA) at Tufts University found in a recent study that low intake of EPA and DHA intake was predictive of cognitive decline over 2 years.(7)
Other large epidemiological studies have shown that consuming fish is inversely related to the development of Alzheimer’s disease, whereas too much Omega 6 on the other hand was associated with cognitive decline.(8,9)
One size does not fit all
The best known genetic variant affecting the onset of Alzheimer’s disease is the ApoE-ε4 allele. Those with this genetic risk factor seem to be less protected by the consumption of fish.(10) There were limited associations between the amount of PUFAs found in the brains of those with mild cognitive impairment compared to those with Alzheimer’s disease and those with no impairment. Stress can also amplify how we respond to PUFA metabolism especially when faced with deficiency.(8)
Gender also appears to differentially play a role whereby females have significantly lower blood levels of EPA, but significantly higher DHA than males.(1)
These data suggest that we are all unique in how we metabolize PUFAs which has implications for how much to supplement. Fatty acid testing is available to better understand your profile and unique requirements.(11)
Alcohol and cognitive function – good or bad?
When it comes to alcohol the news is both good and bad. Take the example of red wine. On the one hand resveratrol found abundantly in grape skins has neuro-protective properties over and above its role as an antioxidant in helping to protect against cognitive decline.(12) On the other hand ethanol exposure promotes brain inflammation and neuron cell death by inhibiting the synthesis of phosphatidylserine – a vital component of brain cell membranes.(13)
Perhaps, a few midweek grape juice substitutions are in order for the sake of the brain?
Good sources of Omega 3 PUFAs
The best source of Omega 3 comes from real food where it is packaged as nature intended with other nutrients that help in its absorption and assimilation.
Fish contains good amounts of vitamins A, B12, B3 and folate. If it is wild caught salmon it contains a ratio around 10:1 Omega 3 to Omega 6 compared to farmed salmon which is closer to 2.5:1. Other good choices are sardines and mackerel.(14)
The smaller fish tend be less toxic because they are lower in food chain and have less time to accumulate heavy metal toxins like mercury.
It also contains more antioxidant nutrients and enzymes which is important because their many unsaturated bonds PUFAs are susceptible to oxidation (think rust) – the cause of free radicals.(15,16)
Fish oil supplements have become popular since their many health benefits have become more widely reported. Liquid oils such as cod liver or salmon are more stable, less prone to oxidation and better absorbed than fish oil in capsules.(17)
Krill oil has additional benefits. It has even higher bioavailability than fish oil due to the presence of phospholipids which enables them to be absorbed intact from the gastrointestinal tract. In fact, you only need two-thirds the amount of Krill oil to have the same level of absorption of DHA and EPA.(18)
Krill oil also contains the readily-absorbable, potent antioxidant astaxanthin which can reduce oxidative stress a component of cognitive dysfunction.(19)
Good plant-based sources of Omega 3’s include flax, chia and hemp seeds and nuts especially walnuts. Some people think that it is no coincidence that the nut resembles the organ that it is best designed to protect, suggesting that when in doubt we should always look to nature-made solutions.
While their conversion to DHA and EPA is less efficient they will still protect against deficiency is regularly consumed in the diet.
Algal oil from algae was shown to be nutritionally equivalent to fish and therefore a good choice for vegetarians.(20)
The bottom line
1. Liu JL et al. Pathways of Polyunsaturated Fatty Acid Utilization: Implications for Brain Function in Neuropsychiatric Health and Disease. Brain Res. 2015; 9:220–246. doi:10.1016/j.brainres.2014.11.059.
2.Talahalli RR et al. Lower efficacy in the utilization of dietary ALA as compared to preformed EPA + DHA on long chain n-3 PUFA levels in rats. Lipids. 2010;45(9):799-808.doi: 10.1007/s11745-010-3464-6
3.Gerster H. 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. 1998;68(3):159-73.
4.Simopoulos AP. Evolutionary aspects of diet, the omega-6/omega-3 ratio and genetic variation: nutritional implications for chronic diseases. Biomedicine & Pharmacotherapy. 2006; 60 (9): 502–50. doi:10.1016/j.biopha.2006.07.080
5. Blasbalg TA et al. Changes in consumption of omega-3 and omega-6 fatty acids in the United States during the 20th century. Am J Clin Nutr 2011;93:950–62.doi: 10.3945/ajcn.110.006643
6.Grosso G et al. Omega-3 Fatty Acids and Depression: Scientific Evidence and Biological Mechanisms. Oxid Med Cell Longev. 2014;.doi: 10.1155/2014/313570
7.Science Daily. Diet can predict cognitive decline, researchers say. Available at: http://www.sciencedaily.com/releases/2014/04/140427121051.htm
8.Cunnane SC et al. Plasma and Brain Fatty Acid Profiles in Mild Cognitive Impairment and Alzheimer’s Disease. J Alzheimers Dis. 2012 ; 29(3): 691–697. doi:10.3233/JAD-2012-110629.
9.Morris MC et al. Fish consumption and cognitive decline with age in a large community study. Arch Neurol. 2005;62(12):1849-53
10. Chouinard-Watkins R et al. Disturbance in uniformly 13C-labelled DHA metabolism in elderly human subjects carrying the apoE e4 allele. Brit J Nutr 2013:110:1751–1759
11. Fatty Acid testing from Genova Labs: https://www.gdx.net/product/essential-metabolic-fatty-acids-analysis-nutritional-test-blood
12.Sun AY et al. Resveratrol as a Therapeutic Agent for Neurodegenerative Diseases. Mol Neurobiol. 2010; 41(2-3): 375–383. doi:10.1007/s12035-010-8111-y.
13.Akbar M et al. Ethanol promotes neuronal apoptosis by inhibiting phosphatidylserine accumulation. J Neurosci Res. 2006;15;83(3):432-40.
15.Ruxton CHS et al. The health benefits of omega-3 polyunsaturated fatty acids: a review of the evidence. J Hum Nutr Diet.2007;20 (3):275-285
16.Daley CA et al. A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef. Nutr J. 2010;10;9:10.doi: 10.1186/1475-2891-9-10
17.Ritter JC et al. Oxidation Rates of Triacylglycerol and Ethyl Ester Fish Oils. Journal of the American Oil Chemists’ Society.2015;92(4): 561-569
18. Ulven SM et al. Metabolic Effects of Krill Oil are Essentially Similar to Those of Fish Oil but at Lower Dose of EPA and DHA, in Healthy Volunteers. Lipids. 2011;46:37–46.doi 10.1007/s11745-010-3490-4
19. Dose J et al. Free Radical Scavenging and Cellular Antioxidant Properties of Astaxanthin. Int J Mol Sci. 2016;14;17(1):pii: E103. doi: 10.3390/ijms17010103
20. Arterburn LM et al. Algal-oil capsules and cooked salmon: nutritionally equivalent sources of docosahexaenoic acid. J Am Diet Assoc. 2008;108(7):1204-9. doi: 10.1016/j.jada.2008.04.020