Prior research has linked dietary factors to the management and reduction of risk for Alzheimer’s disease. One dietary influence studied is docosahexaenoic acid (DHA), an omega-3 fatty acid found in fatty fish such as salmon. DHA has been linked to the improvement of features associated with Alzheimer’s disease, such as neuroinflammation and brain glycose hypometabolism, amongst others. While a body of evidence has already linked DHA to the prevention or delay of Alzheimer’s disease, a new study published in the journal Nutrients by Sala-Vila et al. offers further corroborating evidence.
Study Aims and Methodology
The study in question was set out to measure Alzheimer’s disease and all-cause dementia development on 1490 Americans over the age of 65 from the Framingham Health Study in Framingham, Massachusetts. Participants were carefully chosen and followed for a medial of 7.2 years after the study to observe incident dementia onset.
While the study did not set out to, nor could it establish causality, it took steps to ensure objectivity in measures of DHA. Instead of relying on dietary intake questionnaires, which can often be subjective and unreliable, the researchers conducted Red Blood Cell (RBC) analysis, wherein they quantified 27 fatty acids, and expressed DHA as a percentage of the total RBC fatty acids.
Results and Implications
The results indicated that high omega-3 DHA levels (typically associated with the highest dietary intake) were linked to a significant reduction in the risk of developing Alzheimer’s disease and all-cause dementia. In fact, those in the top quintile had a staggering 49% reduction in risk for developing Alzheimer’s compared to those in the lowest quintile. This number was also extremely high for the development of all-cause dementia, reaching a risk reduction of 44%.
When comparing low and high quintile DHA levels, it was found that the estimate was a reduction of 4.65 years when it comes to Alzheimer’s and 4.03 years for all-cause dementia. It was also deduced that for those carrying the ApoE4 gene – the strongest known risk factor gene for Alzheimer's disease – the reduction for Alzheimer’s and all-cause dementia was 7.59 and 7.30 years, respectively.
The Sala-Vila et al. study clearly shows that those with high DHA omega-3 levels (above 6.1%) in their red blood cells had about 4.7 more years of life free of Alzheimer’s as compared to those with levels below 3.8%. This was in addition to halving the risk of developing Alzheimer’s and dementia.
The results from this study as well as prior research, show a strong association between DHA levels and a reduced risk of dementia. As such, the current body of research suggests that high DHA intake could be an excellent strategy for the prevention of Alzheimer’s disease and dementia. The study’s results are especially important for those carrying the ApoE4 gene since there was a stronger association for carriers as compared to non-carriers.
The results from this study as well as prior research, show a strong association between DHA levels and a reduced risk of dementia.
While fatty fish such as salmon and tuna are rich dietary sources of omega-3 DHA, eating enough quantities often presents challenges. Tuna and swordfish, for example, contain high levels of mercury and other harmful pollutants; and daily salmon consumption may not be sustainable both in terms of monetary cost as well as environmental impact. As such, daily supplementation with fish oil or concentrated omega-3 fatty acids currently represents the best-known strategy for increasing omega-3 RBC levels.