OMEGA-3 Fatty Acids and Alzheimer's Disease

Omega-3 fatty acids are a family of polyunsaturated fatty acids that are important components of cell membranes. Omega-3 fatty acids are particularly important for the health of the brain. They are considered ‘essential’ fatty acids and can be found in some foods, especially fatty fish such as mackerel, lake trout, herring, sardines, albacore tuna and salmon. Tofu and other forms of soybeans, canola, walnut and flaxseed, and their oils. contain alpha-linolenic acid (LNA), which the human body can convert into Omega-3 fatty acid. The Food and Drug Administration considers DHA to be GRAS (generally recognized as safe).

Docosahexaenoic acid (DHA) is the most abundant Omega-3 fatty acid in the brain. It is especially enriched in synaptic fractions of brain, which is the portion where messages are transmitted from nerve to nerve. The synapse is important for new learning and for memory functions. DHA is found in all tissues; but is most abundant in nerves, retina (e.g. the eye) and in the conducting tissue of the vascular system. DHA is important in cardiovascular health and in infant development and is often an additive to baby formula and vitamin supplements for infants.

Several studies have documented the cognitive health benefits of Omega-3s. Fish consumption has been associated with a lower risk of Alzheimer disease. One study of over 1,000 people followed over a 10 year period showed that consuming fish at least 3 times a week was associated with increased plasma DHA levels and a 48% reduction in Alzheimer disease. Other studies have found similar association between fish intake and reduced risk of Alzheimer disease and it has usually been attributable to DHA levels and not to the levels of other Omega-3s. Low levels of DHA have been found in Alzheimer’s patients.

DHA has also been studied in animal models of Alzheimer disease. In one model, a transgenic mouse is bred to have large amounts of the protein amyloid, which is found in plaques in the brains of patients with AD. In a recently published study, mice that were fed diets rich in DHA had lower levels of beta amyloid and tau protein amyloid in their brains than mice that were not. In other animal studies, DHA protects cells against “oxidative” damage, which is thought to be the damage caused by the aging process as well as by disease.

Ongoing studies are examining the effect of DHA in healthy individuals and on cognition, depression and other health factors such as cardiovascular risk factors.

Because dietary DHA is so important to brain levels of DHA, several studies are underway to examine the effects of an oral dose of DHA in Alzheimer’s disease. Initial results are mixed. One small study in patients with Alzheimer’s disease which used 1.7 g of DHA in combination with another Omega-3, (EPA: 0.6 g) was unable to show a benefit. This may be because the study only lasted 6 months, and it can take up to 10 months to increase DHA levels in the brain. Currently, the ideal amount to take isn’t clear, and higher doses may be needed.

Since there is some data to suggest that it may be helpful in Alzheimer’s disease, the National Institute of Aging is now supporting a large multi-center clinical trial of DHA for the treatment of Alzheimer’s disease. This study, which will enroll 400 subjects with mild to moderate Alzheimer’s disease and follow them for 18 months, will be conducted at 40 sites throughout the country including all three ADC partners in NYCARE here in NYC. The DHA dose in this study is 2 grams, which is estimated to cost approximately $150/month. It is an especially pure version of DHA. Subjects will be randomized to DHA or placebo with more receiving the DHA than the placebo. This study will provide important information about this formulation and will determine if it has a benefit in AD.

It is important to realize that in the absence of clinical trial results,we can not be sure about the benefits of any products. For more information on this study,please go to ClinicalTrials.gov or see the studies listed in this section.

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