Omega-3-Rich Diet May Protect Against Alzheimer's Disease

Megan Brooks

May 04, 2012

May 4, 2012 — Increased consumption of omega-3 polyunsaturated fatty acids (PUFA) correlate significantly with lower plasma levels of beta-amyloid 42 (Aβ-42) in elderly individuals without dementia, researchers found.

The association of higher omega-3 intake and lower plasma Aβ-42 they observed was independent of age, sex, ethnicity, education, and APOE genotype and has been "linked with reduced risk of incident Alzheimer's disease (AD) and slower cognitive decline in our cohort," they note.

The study, from Nikolaos Scarmeas, MD, MSc, associate professor of neurology, Columbia University Medical Center in New York City, and colleagues was published online May 2 in Neurology.

"We demonstrate here that there is an association between what we eat and levels of amyloid in our blood," Dr. Scarmeas told Medscape Medical News. "The amount of omega-3 that we consume may relate to levels of amyloid in our system, an argument suggesting a possible direct relation with Alzheimer's type of pathology," he added.

The WHICAP Cohort

The findings stem from the Washington Heights/Hamilton Heights Columbia Aging Project (WHICAP), a large community-based project investigating the antecedents, biologic risk factors, genetics, and course of cognitive aging and dementia. A total of 1219 cognitively healthy multiethnic participants older than age 65 years provided information on their diet 1.2 years, on average, before plasma levels of Aβ were assessed.

The study team used linear regression models adjusted for relevant confounders to analyze associations between Aβ-40 and Aβ-42 levels and dietary intake of 10 nutrients, including saturated fatty acids, monounsaturated fatty acids (MUFA), omega-3 PUFA, omega-6 PUFA, vitamin E, vitamin C, beta-carotene, vitamin B12, folate, and vitamin D.

They report that participants with higher plasma levels of Aβ-40 and Aβ-42 were older and less educated and had lower intakes of omega-3 PUFA, omega-6 PUFA, and MUFA. Participants with higher omega-3 or omega-6 PUFA or MUFA intake had higher education, were more likely to be white or black and less likely to be Hispanic, and had lower levels of Aβ-42. Those with higher omega-3 PUFA also had lower levels of Aβ-40.

In unadjusted models that simultaneously included all nutrients, higher intake of omega-3 PUFA was associated with lower levels of Aβ-40 (? = -24.74; P < .001) and Aβ-42 (? = -12.31; P < .001).

In the fully adjusted model, omega-3 PUFA remained a strong predictor of Aβ-42 (? = -7.70; P = .02), whereas its association with Aβ-40 was attenuated (? = -10.13; P = .13).

The other investigated nutrients were not associated with plasma Aβ levels.

Mounting Evidence

Dr. Scarmeas and his colleagues say their observations are consistent with results observed in animal studies, "pointing to a beneficial role of dietary omega-3 PUFA in brain pathology."

They also note that in a prior study using the WHICAP cohort, also reported by Medscape Medical News, they observed a lower risk of incident AD, mild cognitive impairment (MCI) and progression from MCI to AD in subjects who adhered more to a Mediterranean-style diet, characterized by a high intake of omega-3-rich fish.

They also showed previously that a "dietary pattern" characterized by high omega-3 PUFA (and other nutrients) was associated with a 40% reduced risk for incident AD. They also reported recently that increasing intake of omega-3 PUFAs was associated with a 20% to 30% lower risk for dementia (Alzheimer Dement. 2011;7:S296-S297).

The researchers conclude that the "potential beneficial effects of omega-3 PUFA intake on AD and cognitive function in the literature might be at least partly explained by an Aβ-related mechanism."

In terms of clinical implications, Dr. Scarmeas cautioned that he's "not sure about direct clinical applications because we are not sure about causality (not a clinical trial) and we relate aspects of diet to blood, not brain levels of amyloid (but they are related to a certain extent)."

"Determining through further research whether omega-3 fatty acids or other nutrients relate to spinal fluid or brain beta-amyloid levels or levels of other (AD) related proteins can strengthen our confidence on beneficial effects of parts of our diet in preventing dementia," Dr. Scarmeas said in a statement.

The study was supported by the National Institute on Aging. The authors have disclosed no relevant financial relationships.

Neurology. Published online May 2, 2012. Abstract

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