The Whole Story
Research has suggested for many years that there is a relationship between dietary omega-3 fatty acid (FAs) intake and Alzheimer’s disease. The relationship appears to be that a higher ongoing intake is associated with a reduced risk of the disease. However, to put this in an accurate perspective it has been a markedly reduced intake that actually increases the risk. The diet of our ancient ancestors was thought to contain approximately 12-15 grams/day of these fatty acids. The shift from the hunter/gatherer diet to that of a modern agricultural based processed food diet has reduced this to under 0.5 gram/day or an approximate 25-fold reduction.
Omega-3 FAs relate to brain health through two important mechanisms. The first is they are involved in balancing inflammatory signaling
in the body. Two classes of
fatty acids, the omega-3s and the
omega-6s suppress and activate inflammation respectively. If we have an infection, inflammation
activates to suppress it. As it
resolves, the body should switch to anti-inflammatory, pro-resolving (healing)
state. If the levels of omega 6 and 3
FAs in the body are balanced this natural orchestration occurs. While the omega 6:3 ratio of our ancestral
diet was 1:1 allowing this process, the current diet has an omega 6:3 ratio of
16:1 which is very pro-inflammatory.
The significance of this change with Alzheimer’s disease is that inflammation is a primary driving mechanism of the production of beta amyloid, the abnormal protein plaque that builds up in the brain destroying neurons. Numerous studies have demonstrated the ability of omega-3 FAs to reduce inflammatory signaling.
Omega-3 FAs also play a role in cell membrane stability and signaling. Brain cell membranes normally take up and store high amounts of omega-3 fatty acids particularly DHA. The presence of higher amounts of the FAs help the cells communicate better with other neurons which is the essential process of their activity.
Even understanding the underlying mechanisms through which omega-3 FA balance affects the brain, the real question remains is if there is a relationship between levels of these fatty acids and Alzheimer’s disease. Intense research over the past 5 years has answered much regarding this issue.
Several studies have looked at long-term omega fatty acid intake and the risk of subsequently developing Alzheimer’s disease. They have consistently found that greater long-term intake of omega-3 fatty acids reduces the risk of developing Alzheimer’s disease. Other studies have examined the relationship of omega-3 fatty acid intake and the early functional changes that occur in the brain in Alzheimer’s disease. One of the primary deficits that occurs in the disease is impaired spatial memory. This is the loss of the ability to know where you are in relation to familiar places. For example, one of the early presenting symptoms of Alzheimer’s disease can be episodes of traveling down a familiar street or road and not knowing which exit or turn needs to be taken to get home or to another familiar place.
A study of older adults compared their intake of omega-3 and omega-6 fatty acids to their performance on a spatial memory test.(1) The higher intake of omega-3 fatty acids and a lower omega-6 to omega-3 intake ratio strongly predicted performance on the spatial memory test. Subjects also completed a standard cognitive functioning test used in the diagnosis of Alzheimer’s disease, the Montreal Cognitive Assessment test (MoCA). Poor omega-3 fatty acid intake and a high omega-6:omega-3 ratio was associated with a score 4 points lower on the 30 point MoCA test. This is the amount of cognitive decline which differentiates the early phase of Alzheimer’s disease from normal cognition!
While generally higher intake of omega-3 fatty acids and a lower omega-6:omega-3 ratio is important in preventing and managing cognitive decline, how to do it is a little more complex. The complexity comes in answering the question, “how much?” The research suggests that it is the tissue levels of fatty acids that predicts risk, and there is not a uniform relationship between dietary intake and cell membrane levels. This is related to genetic mediated differences in metabolism.
The brain is not readily accessible to examine cell membrane fatty acid levels. Fortunately, cell membrane levels of the omega-6 and omega-3 fatty acids tend to be similar across several cell types. Red blood cells are very reflective of overall cell fatty acid levels, and they are easily accessible in a simple finger prick derived sample. Using this test to determine cell levels of omega-3 fatty acids and the omega-6:omega-3 ratio can be accurately done.
The utility of this test in Alzheimer’s treatment and prevention was recently demonstrated.(2) The omega-3 index test was correlated with brain PET scans using a tracer that highlights beta amyloid, the abnormal protein that causes the brain degeneration in Alzheimer’s disease. Lower cell omega-3 levels and higher omega-6:omega-3 ratios correlated with higher levels of beta amyloid levels in the brain. The researchers commented that the omega-3 index predicted the build-up of brain plaque in those who were still cognitively normal.
The first test
below shows a very low omega-3 cell level at 3.72%. The ideal preventative and treatment level is
8-12%. The second test shows normal test
with an omega-3 level of 11.0%.
The true value is to know the therapeutic level of omega-3 fatty acids to target the ideal cell levels. As different individuals respond differently to specific dietary levels, a second test is done 4-6 months after beginning supplementation to ensure the target level is obtained.
To summarize what is understood about the relationship between omega-3 and omega-6 fatty acids levels and Alzheimer’s disease risk and treatment, we now better understand the following:
· Omega-3 fatty acid intake and cell membrane levels correlate both with the risk of developing the disease.
· The omega-6:omega-3 balance correlates with the balance between inflammatory and anti-inflammatory signaling which increases both the risk of development and the risk of progression of the disease.
· Dietary and supplemental intake does not directly correlate with cell levels, so adequate levels should be determined by blood cell testing.
1) Andruchow N, Konishi K. A LOWER RATIO OF OMEGA-6 TO OMEGA-3 FATTY ACIDS PREDICTS BETTER HIPPOCAMPUS-DEPENDANT SPATIAL MEMORY AND CONGITIVE STATUS IN OLDER ADULTS. Neuroipsychology, 2017.
2) Gooze et al. ALTERATIONS IN ERYTHROCYTE FATTY ACID COMPOSITION IN PRECLINICAL ALZHEIMER’S DISEASE. Nature:Scientific Reports, 2017;7:676.
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