New study shows link between brain DHA and Alzheimer's
Omega 3 levels in both brain and blood, specifically Omega 3 DHA, have been linked in many studies to reduced risk of Alzheimer's Disease and All Cause Dementia. The broadest study to date of 899 men and women showed that in the Framingham Cohort the risk of Dementia and Alzheimer's decreased by 47% if your Omega 3 DHA Phosphatidyl Choline blood levels are in the upper 25% of the population score. However, blood levels are not necessarily brain levels, since many hurdles must be overcome before the good Omega 3 fats end up in the brain.
So why not look at the fats in the brain? That’s what a group of researchers did in March 2017. They analyzed brain samples of 44 people from 3 groups: 15 with Alzheimer's Disease, 14 people with Alzheimer's but with no symptoms, and 15 Alzheimer's free individuals. The purpose of the study was to discover if metabolic processes (like the formation of Alzheimer's plaque and tau) impacted the levels of unsaturated omega 6 and omega 3 levels. Or that the reverse was true: that fatty acids impacted the formation of plaque and tau.
Although the size of the study was a limitation, the results were clear: there’s a strong correlation between unsaturated omega 3, 6 and 9 and Alzheimer's. The levels of Omega 6 (AA, LA) and Omega 9 (OLA) were decreased, as well as the Omega 3 EPA levels were lower. However, very surprisingly the levels of the Omega 3 brain fat DHA were higher in Alzheimer's patients. This result even puzzled the researchers, because most other studies show that DHA protects the brain against inflammation (which is what Alzheimer's is). The only explanation they give for this paradoxical outcome is that they measured free fatty acids and not fatty acids bonded to phospholipids (as they function in the brain). Therefore, their puzzling outcome begs the following two questions:
Why was Omega 3 DHA also relatively decreased in the asymptomatic Alzheimer's group? Could that mean that lack of DHA could play a role in the earlier stages of the disease?
If DHA protects the brain against inflammation, and when Alzheimer's is inflammation and higher levels of DHA are observed in Alzheimer's patients, then could it be that Alzheimer's patients do not (efficiently) use the available DHA for the production of anti inflammatory brain protectants?
The researchers agree with the scientific consensus that Omega 3 DHA protects the brain:
“Studies have shown that DHA and EPA containing phosphatidylcholines (phospholipids) are reduced in abundance in the blood of patients with Alzheimer's Disease. It has been reported that (…) enzymes that break down unsaturated fatty acids (as measured in this study), have all been shown to be up-regulated (increased) in patients with Alzheimer's Disease, potentially explaining the decrease in the observed unsaturated fatty acids. Breakdown of EPA and other unsaturated fatty acids by (enzymes) leads to the production of prostaglandins (…), leukotrienes, and (…) epoxyeicosatrienoic acid, all of which have been associated with a range of diseases including Alzheimer's. The breakdown of DHA by these enzymes produces resolvins, maresins, and protectins, which have been shown to be protective against numerous diseases, including in Alzheimer's Disease.”
Although the study result may look confusing at first (higher DHA levels in Alzheimer's patients), the study fails to explain their surprising result about higher DHA brain levels in Alzheimer's. Most likely the answer is that both Alzheimer and higher DHA levels have the same cause, and not that one (DHA) is causing the other (Alzheimer).
Keep in mind that krill oil is the best source for Omega 3 DHA phospoholipids (look for 40%). Also keep in mind that fish oil has zero Omega 3 in phospholipid form (as in the brain). Almost all fish oil is in triglyceride form. Look here for a good krill oil source with a $10 coupon (use coupon code 10Whistler at check out).
Source: Association between fatty acid metabolism in the brain and Alzheimer disease neuropathology and cognitive performance: A nontargeted metabolomic study by Stuart G. Snowden et. al. PubMed 1002266. March 21, 2017.