It's difficult to imagine that a simple dietary intervention could mean less Alzheimer’s disease but that is why observational studies and epidemiology claims are placed into the exploratory pile until science can take a look.

A new paper correlates people with a higher  red blood cell (RBC) docosahexaenoic acid (DHA levels as 49% less likely to develop Alzheimer’s disease vs. those with lower levels, especially for those carrying the ApoE4 gene, which is also a risk factor for Alzheimer's. You know that correlation is not causation so modifying two risk factors with unclear biological meaning may or not be better than doing nothing and hoping for the best. 

The prospective observational study used data from the Framingham Offspring Cohort, no one was actually examined, and included 1,490 dementia-free participants aged ≥ 65 years old. The authors looked at red blood cell (RBC) docosahexaenoic acid (DHA) with incident Alzheimer’s Disease (AD), while also testing for an interaction with APOE-ε4 carriership. Risk for incident AD in the highest RBC DHA quintile (Q5, >6.1%) was 49% lower compared with the lowest quintile (Q1, <3.8%). An increase in RBC DHA from Q1 to Q5 was predicted to provide an estimated 4.7 additional years of life free of AD.

They also note that an increased intake of DHA might lower risk for developing AD, particularly in higher-risk individuals such as those carrying the APOE-ε4 allele, suggesting that they may benefit more from higher DHA levels than non-carriers.

“Our study is in line with that of Tan et al. who reported cross-sectional associations with RBC DHA on cognitive performance and brain volume measurements (with higher DHA being associated with beneficial outcomes) in the same cohort as studied here,” said William S. Harris, PhD, President of FARI, and senior author on this recent study.

“Most interestingly, 15 years ago similar findings were reported by Schaefer et al. in the parents of the individuals who were the focus of this present investigation (i.e., the Original Framingham Heart Study cohort). Schaefer et al. reported that participants in the top quartile of plasma phosphatidylcholine DHA experienced a significant, 47% reduction in the risk of developing all-cause dementia compared with those with lower levels,” Harris continued. “Similar findings a generation apart in a similar genetic pool provide considerable confirmation of this DHA-dementia relationship.”