Epidemiological studies indicate that diets high in saturated fatty acids are linked to cognitive decline, while consumption of high levels of fish and omega-3 fatty acids are associated with improved cognitive function. Because cod liver oil is rich in omega-3 fatty acids, there is interest in it as a treatment for Alzheimer's disease.
Omega-3 Fatty Acids
There are many omega-3 fatty acids. One of the most studied is docosahexaenoic acid, or DHA. A study of 266 men and women published in the "Journal of Nutrition, Health & Aging" in 2011 found that people in the top third of all subjects for plasma DHA levels had significantly lower risk of all forms of dementia and 60 percent lower risk of Alzheimer's disease than those whose plasma DHA levels were in the bottom third. A high dietary intake of DHA also correlated with significantly reduced risk of all forms of dementia. On the other hand, an April 7, 2010 article published in "Clinical Interventions in Aging" reviewed clinical studies on omega-3 fatty acid supplementation and concluded that they failed to find an overall positive effect. However, the studies did suggest that whether omega-3 supplementation is beneficial depends on the stage of the disease, other components of the diet and whether or not patients carry genes predisposing them to Alzheimer's disease.
Many Pieces to the Alzheimer's Puzzle
According to a November 2010 article in the "Expert Review of Neurotherapeutics," several approaches are needed to prevent Alzheimer's disease. The authors list physical activity, mental stimulation and control of hypertension as among the most important steps to take, but they recommend more study of omega-3 fatty acids and the Mediterranean diet as well.
Interaction Between Genes and Diet
Whether cod liver oil or anything else will work as treatment for Alzheimer's disease may depend on the genetic makeup of the people involved. According to a May 2011 review published in "Current Alzheimer's Research," people who carry a gene known as the APOE4 allele, which predisposes its carriers to develop Alzheimer's disease, seem to respond differently to fatty acids than do people who do not carry the gene. The authors of the study conclude that more research is needed before definite conclusions can be drawn about this issue.
Cautions
According to the University of California Wellness letter, there is no evidence to indicate cod liver oil is an effective treatment for Alzheimer's disease, although it may offer some protection against heart disease and stroke. The studies showing that omega-3s exert a neuroprotective effect are usually epidemiological studies in which people with higher omega-3 levels have healthier diets generally. Consult your doctor before considering supplementation with cod liver oil. Cod liver oil is very high in vitamin A, which, if given in large doses, can weaken bones and increase risk of fractures. Since many Alzheimer's patients are elderly women who may also be at risk for osteoporosis, care needs to be taken not to give too much of this substance.
References
- UC Berkeley Wellness Letter:Wellness Guide to Dietary Supplements: Cod Liver Oil
- "Current Alzheimer's Research"; Dietary Omega 3 Polyunsaturated Fatty Acids and Alzheimer's Disease: Interaction with Apolipoprotein E Genotype; P. Barberger-Gateau, et al.; May 23, 2011
- "Journal of Nutrition, Health & Aging"; High Dietary and Plasma Levels of the Omega-3 Fatty Acid Docosahexaenoic Acid Are Associated With Decreased Dementia Risk: the Rancho Bernardo Study; L.B. Lopez, et al.; 2011
- "Expert Review of Neurotherapeutics"; Is Dementia Preventable? Focus on Alzheimer's Disease; Y. Barak, et al.; November 2010
- "Clinical Interventions in Aging"; Omega-3 Fatty Acids: Potential Role in the Management of Early Alzheimer's Disease; J.G. Jicha, et al.; April 7, 2010
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