By Maureen Williams, ND
Healthnotes Newswire (January 5, 2006)—Older people who eat fish regularly lose cognitive function more slowly than those who don’t, according to a study published in Archives of Neurology (2005;62:1–5).
As we age, our mental abilities gradually decline. The rate of loss of mental capacity is partly determined by genetics, but is also influenced by the presence of neurotoxins, such as heavy metals (lead, mercury, aluminum) and some chemicals, and neuroprotective substances, such as antioxidants.
Certain fatty acids have been found to lower the risk of Alzheimer’s dementia and cognitive decline. The omega-3 fatty acids found in fish, eicosapentaenoic acid (EPA) and especially docosahexaenoic acid (DHA), have been shown to play an important role in neurological development and normal brain functioning. Several studies have found that eating fish can reduce the risk of dementia, a progressive condition marked by memory loss and poor cognitive functioning.
The current study included 3,718 people 65 years and older. Participants underwent an interview and cognitive testing at the beginning of the study, which were repeated after 3 and 6 years. Food questionnaires were answered an average of 1.2 years after the first assessment and the results were used to determine the amount of fish eaten weekly as well as the nutrient composition of the diet.
People who ate fish two or more times per week had the slowest rate of cognitive decline—approximately 13% slower than in those who ate fish less than once per week. Those who ate one fish meal per week had a 10% slower rate of cognitive decline than those who ate fish less than once per week. Those who ate high amounts of other types of fats, however, including saturated fats, polyunsaturated fats from foods other than fish, and trans fats, did not benefit from eating one or two fish meals per week.
The results of this study suggest that eating fish might slow the rate of cognitive decline associated with aging. Even one fish meal per week had a significant benefit. It further appears from these findings that eating a diet high in fats from other sources diminishes this effect. Two other factors might limit the benefits of eating fish: first, omega-3 fatty acids are known to be easily oxidized and could deplete neuroprotective antioxidants; and second, the high levels of neurotoxic heavy metals such as mercury in the water have contaminated fish and can accumulate in people who eat fish.
Finding the upper limit of fish consumption that protects against cognitive decline, and determining whether this can be affected by antioxidant intake or choosing fish with lower heavy metal levels, would be interesting topics of future research.
Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, VT, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.