October 24, 2006
Nutritional supplements containing omega-3 fatty acids, or omega-3s, the type of heart-healthy fats found in fish oils, may provide benefits for the very earliest stages of Alzheimer's disease. Omega-3s, however, did nothing to stem cognitive decline in those with more advanced stages of the disease. The findings were published in the Archives of Neurology, a journal from the American Medical Association. It is not known whether omega-3 oils reduce the risk of developing Alzheimer's in healthy people.
Researchers at the Karolinska Institute in Stockholm, Sweden, studied the effects of supplements containing omega-3s in 174 people with mild to moderate Alzheimer's disease. For six month, 89 men and women in the earlier stages of Alzheimer's took omega-3 supplements, while another group of 85 took a look-alike placebo pill. Then, for an additional six months, both groups took the omega-3 pills.
The pills contained two key types of omega-3s believed to benefit the heart and, possibly, the brain: DHA, or docosahexaenoic aicd (1.7 gram dose per pill), and EPA, or eicosapentaenoic acid. Both are thought to have disease-fighting effects, but this study used a higher concentration of DHA than many earlier reports.
Study participants were given regular physical exams, including blood tests and blood pressure checks. They also took detailed tests of memory and thinking skill at the start of the study, then again at the six- and 12-month marks.
Benefits for Very Mild Disease
After six months, there was no overall difference in the rate of memory loss between the two groups. However, among a small sub-group of 32 men and women who were in the very earliest stages of Alzheimer's at the start of the study, the omega-3s did appear to provide some benefits. Those individuals taking the fatty acids experienced less mental decline after six months compared to those taking a placebo. Furthermore, those with very mild memory problems who were taking a placebo during the first six-month period showed less mental decline during the latter six-month portion of the study, when they were taking the omega-3s.
The omega-3 supplements appeared to be very safe and well tolerated. There were no undue complaints about side effects. There were also no problems relating to blood tests or blood pressure.
Researchers speculate that the DHA and EPA in omega-3s may quell inflammation, which is emerging as a possible underlying cause of heart disease and other ills, including Alzheimer's disease. "The mechanisms by which omega-3 fatty acids could interfere in Alzheimer's disease features are not clear, but since anti-inflammatory effects are an important part of the profile of fish oils, they are conceivable also for Alzheimer's disease," the authors write.
Population studies suggest that people who eat a lot of fish, especially oily deep water fish like salmon and mackerel, have a lower rate of heart disease as well as Alzheimer's. [See the article, "A Fish-Rich Diet May Help Keep the Mind Sharp"] And in animal studies, DHA has been shown to improve cognitive performance. Diets high in DHA also led to a reduction in beta-amyloid, the sticky protein that builds up in the brains of those with Alzheimer's, in mice.
Emerging evidence suggests that the inflammation-fighting properties of omega-3s and fish oils may be most important during the very earliest stages of Alzheimer's disease. There may be a critical period two or more years before patients develop full-blown Alzheimer's symptoms when levels of inflammation are high, and when fish-oil omega-3 supplements may be most effective. After this time, the authors write, "when the disease is clinically apparent, the neuropathologic involvement is too advanced to be substantially attenuated by anti-inflammatory treatment."
The researchers point out that more study is needed before fish oils or supplements rich in DHA and EPA can be recommended for early Alzheimer's or for mild cognitive impairment, a less severe form of memory loss that sometimes progresses to Alzheimer's disease. They call for studies in larger numbers of people to explore the potential benefits in halting initial progress of the disease.
Yvonne Freund-Levi, M.D., Maria Eriksdotter-Jonhagen, M.D., Ph.D., Tommy Cederholm, M.D., Ph.D., et al: "Omega-3 Fatty Acid Treatment in 174 Patients With Mild to Moderate Alzheimer Disease: OmegAD Study." Archives of Neurology: Volume 63, October 2006, pages 1402-1408.