Neurological Foundation of New Zealand

Nutritionists recommend fish as part of a healthy diet, and now research shows that omega-3 fatty acids found in the oil of certain fish may also benefit the brain by lowering the risk of dementia. In order to test whether an omega-3 fatty acid can affect the progression of AD, researchers at the National Institute on Aging (NIA), are evaluating one in a clinical trial, the gold standard for medical research.

The study will be conducted in the USA by the Alzheimer’s Disease Cooperative Study. The trial will take place at 51 sites across the US involving 400 participants age 50 and older who have mild AD. Dr Joseph Quinn, Associate Professor of Neurology at Oregon University, is directing the study. Dr Quinn received his undergraduate degree at Harvard and his MD at USCLA.
The researchers are evaluating primarily whether the omega-3 fatty acid DHA (docosahexaenoic acid) slows the progression of both cognitive and functional decline in people with mild to moderate AD. During the 18-month trial, investigators will measure the progress of the disease using tests for cognitive change.

“The evidence to date in animal studies on omega-3 fatty acids and AD warrants further evaluation in a rigorous clinical trial,” says Dr Quinn. “Studies in a mouse model of AD have shown a decrease in amyloid plaques and tau (both involved in AD) when a controlled dose of DHA was ingested. This study is one of a number the NIA is undertaking in the next few years through the ADCS to test compounds that might prevent or delay this devastating disease. By participating in this study, volunteers will make an invaluable contribution to AD research. We are indebted to these volunteers.”

Participants will receive either two grams of DHA per day or a placebo. 60 percent of participants will receive DHA, and 40 percent will get the placebo. Doctors at the 51 research clinic s will monitor the participants in regular visits throughout the trial. To ensure unbiased results, neither the researchers conducting the trial nor the participants will know who is getting DHA and who is getting the placebo. In addition to monitoring disease progression through cognitive tests, researchers will also evaluate whether taking DHA supplements has a positive effect on physical and biological markers of Alzheimer’s, such as brain atrophy and proteins in blood and spinal fluid.

French research published in 2002 in the British Medical Journal followed 1,674 elderly residents of southern France for seven years, studying their consumption of meat versus seafood and the presence of dementia symptoms. The conclusion was that people who ate fish at least once a week had a significantly lower risk of dementia although the study was uncertain if fish consumption protected against dementia, or if dementia prevented the participants from consuming more fish. Individuals with higher education also had a lower risk of dementia and higher consumption of fish, and the relationship between the three factors is uncertain.

In 1994, the UK Committee on Medical Aspects of Food and Nutrition Policy recommended that people should eat at least two portions of fish per week, one of which should be oily fish. In 2004 the UK Food Standards Agency published the recommended minimum and maximum quantities of oily fish to be eaten per week, to balance the beneficial qualities of the Omega 3 fatty acids against the potential dangers of methylmercury (MeHg). The United States Environmental Protection Agency (EPA) Exposure Reference Dose for MeHg is 0.1 micrograms per kg body weight per day. The corresponding limit of blood mercury is 5.8 micrograms per litre.

The EPAs recommendations on maximum consumption of oily fish were up to four 140 gm portions a week for males and women past childbearing age, and up to two portions a week for women of childbearing age and girls. There is no recommended limit on the consumption of white fish.

Fish and shellfish are an important part of a healthy diet. Fish and shellfish contain high-quality protein and other essential nutrients, are low in saturated fat, and contain omega-3 fatty acids. A well-balanced diet that includes a variety of fish and shellfish can contribute to good health and children's proper growth and development. So, women and young children in particular should include fish or shellfish in their diets due to the many nutritional benefits. However, nearly all fish and shellfish contain traces of mercury. For most people, the risk from mercury by eating fish and shellfish is not a health concern. Yet, some fish and shellfish contain higher levels of mercury that may harm a developing nervous system. The risks from mercury in fish and shellfish depend on the amount of fish and shellfish eaten and the levels of mercury in the fish and shellfish. Therefore, the EPA advises pre-menopausal women and children to eat fish and shellfish that are lower in mercury.