NEW YORK (Reuters Health) - High blood levels of omega-3 highly unsaturated fatty acids, which are found in fish oil, may help preserve thinking ability in the elderly, according to the findings of two studies published in the American Journal of Clinical Nutrition. The results were particularly striking among subjects with high blood pressure or high cholesterol levels.

Accumulating evidence suggests that diets that include omega-3 fatty acids, specifically, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), protect against the development of dementia and Alzheimer's disease, according to a Dutch research team. However, the effect of EPA+DHA consumption on thinking ability, or "cognitive function," has received less scrutiny.

So Dr. Boukje Maria van Gelder, from the National Institute for Public Health and the Environment in Bilthoven, and associates evaluated data for 210 healthy men in the "Zutphen Study," who were 79 to 89 years old in 1990 and had normal mental capacity. Their diets were assessed in 1990, and cognitive function was tested in 1990 and again in 1995.

Subjects who ate fish had a slower decline in cognitive function than subjects who did not eat fish.

The investigators conclude that "fish consumption and EPA+DHA intake are not significantly related to cognitive impairment but are significantly related to cognitive decline."

Van Gelder's team recommends the daily consumption of roughly 400 mg of EPA and DHA, found in fish, meat, eggs, leeks, and cereal products.

In the second study, which involved 2,251 older individuals, Dr. May A. Beydoun, at the University of North Carolina at Chapel Hill, and colleagues showed that high blood levels of EPA and DHA are associated with less decline in verbal ability.

In an accompanying editorial, Dr. William E. Connor and Dr. Sonja L. Connor suggest that EPA has anti-clotting and anti-inflammatory properties that work together to help preserve cognitive function.