Omega-3 Fatty Acids and Alzheimer’s Disease

Written by Marcia J. Egles, MD. Omega-3 fatty acids may be beneficial if administered at the onset of Alzheimer’s disease symptoms.

A comprehensive review of the role of omega-3 fatty acids in the treatment of Alzheimer’s disease was recently published. More than thirty relevant studies from the past decade were evaluated in order to assess the best evidence to date on this topic. Considerable evidence supports the conclusion that omega-3 fatty acids may be preventive against Alzheimer’s disease and may be useful against its very early symptoms (1).

Alzheimer’s disease, a progressive and fatal degenerative brain disorder, is the world’s major cause of dementia. The main microscopic changes in the brains of those affected with Alzheimer’s disease are amyloid plaques and “neurofibrillary tangles”. Inflammation and oxidative stress are known to be involved in the development of these abnormalities (2).

Polyunsaturated fatty acids (PUFA), which include omega-3 fatty acids, are known to function as both structural components of nerve cell membranes and as regulators of inflammation, oxidative stress and overall nerve cell health. Amounts of omega-3 PUFAs and omega-6 PUFAs within the membranes can vary with the amounts consumed in the diet and can affect the molecular structure and fluidity of the membranes (3). The body cannot make these essential fatty acids and must obtain them in the diet. Omega-3 fatty acids have become scarce in the modern diet.  Omega-6 fatty acids and saturated fats may be overabundant (4).

DHA, docasahexanoic acid, is the major omega-3 fatty acid found in nerve cells. A large amount of study data from the past decade suggests an important role for DHA in the prevention of a variety of neurological disorders including Alzheimer’s disease (5). Reduced dietary or low brain levels of DHA are associated with accelerated mental decline and dementia. Increased consumption of fatty fish has been associated with decreased risk of Alzheimer’s disease (6). DHA has been shown to be directly involved in the processing of amyloid, the toxic protein which accumulates into amyloid plaques (7).

Although several clinical trials have investigated omega-3 supplements, none have shown benefit for the treatment of established Alzheimer’s disease. These same studies also suggest that benefits from omega-3 fatty acids may depend on the stage of the disease, other dietary factors such too much omega-6 fatty acids, and underlying genetic types some of which might especially benefit from omega-3 fatty acids (1).

Several studies have suggested that omega-3 fatty acids may be beneficial if administered prior to the onset of symptoms or in the earliest stages of cognitive decline (1,8). The 2006 Freud-Levi study, the first large scale, well designed trial of omega-3 supplements, showed benefits to those only in the earliest stages of the disease.

The Canadian Study of Health and Aging (9), rigorously examined plasma fatty acids profiles in 2000. DHA and omega-3 to omega-6 fatty acid dietary ratios were lower in Alzheimer patients. This study was the first to suggest, with later studies to repeat, that the benefits of omega-3 fatty acids may be negated by too much omega-6 fatty acids in the diet. It is estimated that prior to one hundred years ago, western people consumed about twice as much omega-6 as omega-3 fatty acids. Currently, over twenty times as much omega-6 fatty acids as omega-3’s are in typical diets.

Finally, the role of underlying genetics has been increasingly recognized as pertinent to studies involving Alzheimer’s disease and diet. Those possessing the apoprotein epsilon-4 genetic type may be resistent to the efficacy of omega-3 supplements (1).

Source: Jicha, Gregory A., and William R. Markesbery. “Omega-3 fatty acids: potential role in the management of early Alzheimer’s disease.” (2010): 45.

© 2010 Jicha and Markesbery, publisher and licensee Dove Medical Press Ltd. This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited.

Click here to read the full text study.

Posted July 30, 2010.

References:

1. Gregory A Jicha, Omega-3 fatty acids: potential role in the management of early Alzheimer’s disease. Clinical Interventions in Aging March 24,2010. 5 45-61. Dove Medical Press LTD.
   This article is open access with extensive references for the material summarized in this abstract.
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