HealthDay News — People who eat a lot of omega-3 polyunsaturated fatty acids have lower plasma beta-amyloid protein levels, potentially reducing their risk for Alzheimer disease, study results suggest. 

In a cross-sectional study that involved more than 1,200 cognitively normal individuals older than 65 years of age, omega-3 fatty acid intake significantly predicted of plasma levels of the 40- and 42-residue forms of beta-amyloid protein (AB40 and AB42, respectively), Nikolaos Scarmeas, MD, of Columbia University in New York City, and colleagues reported in Neurology.

Participants were enrolled in the Washington Heights/Hamilton Heights Columbia Aging Project in New York City, first recruited in 1992, with a second group enrolled in 1999. The researchers examined dietary intake of 10 nutrients using a detailed diet questionnaire, and conducted beta-amaloid assays on blood samples drawn an average of 1.2 years after dietary information was collected.

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After adjusting for age, education level and other factors, the researchers found a strong but not significant trend between AB40 and omega-3 intake (beta statistic -10.13, P=0.13), but the correlation remained significant for AB42 (beta statistic -7.70, P=0.02).

The researchers also examined the association between plasma amyloid levels and nine other nutrients — folate, beta-carotene, monounsaturated fats, saturated fats, omega-6 fatty acids, and vitamins C, D, E and B12 — but only omega-3 intake was significantly associated with plasma AB40 or AB42.

“The potential beneficial effects of omega-3 [fatty acid] intake on Alzheimer’s disease and cognitive function in the literature might be at least partly explained by an AB-related mechanism,” the researchers wrote.

They acknowledged that plasma beta-amyloid proteins do not necessarily reflect amyloid protein levels in the brain. Other study limitations included the self-reported nature of the dietary data collected, the cross-sectional design and reliance on a single measurement of AB20 and AB42, which may fluctuate during cognitive decline.

Gu Y et al. Neurology 2012; 78: 1-9.