Nov. 8, 2007 -- Eating at least 10 grams of fish per day may make for a sharper mind, new research shows.
That news comes from Norway, where people often eat fatty fish such as salmon, lean fish such as cod, and processed fish such as fish "fingers."
In a Norwegian study, about 2,030 people in their early 70s reported their fish consumption and took various mental skills tests.
People who reported eating on average at least a third of an ounce of fish per day -- 10 grams -- outscored those who skimped on fish, regardless of factors including age, education, and heart health.
Most participants ate fish, and the more fish they ate, the better their test scores were -- up to a point.
Test scores leveled off for people who ate more than about 2.5 to 2.8 daily ounces of fish.
To put that in perspective, 3 ounces of fish is about the size of a checkbook, according to the U.S. Department of Agriculture (USDA).
Omega-3 Fatty Acids and the Aging Brain
The Norwegian researchers -- who included Eha Nurk, MD, of Norway's University of Oslo -- didn't follow the elders over time, so they can't prove that fish boosted test scores.
The omega-3 fatty acids DHA and EPA are found in fatty fish such as salmon and mackerel. Other omega-3 fatty acids called ALAs are found in certain plant foods, including walnuts, flaxseeds, and spinach.
Dutch researchers studied some 800 men and women aged 50-70.
Participants provided blood samples and took mental skills tests at the study's start and again three years later.
Test scores were lower on the follow-up test.
But the drop was gentlest in people with the highest blood levels of omega-3 fatty acids at the study's start.
That pattern held when participants had to quickly respond to mental challenges, but not to general tests of memory, report the researchers.
They included Carla Dullemeijer, MSc, of Wageningen University.
Feel-Good Omega-3 Fatty Acids?
Want a third helping of news on the benefits of omega-3 fatty acids?
A New Zealand study links higher blood levels of the omega-3 fatty acid EPA with better self-reported health.
Those findings come from data on about 2,400 New Zealanders aged 15 and older who gave blood samples and completed a survey on their physical and mental health.
The omega-3 fatty acid EPA was strongly and consistently tied to better self-reported physical health, according to the study.
But the connection between EPA and self-reported mental well-being is "less compelling," write the researchers, who included Francesca Crowe, BSc, of the University of Otago.
All three studies appear in The American Journal of Clinical Nutrition, along with an editorial by Irwin Rosenberg, MD.
In his editorial, Rosenberg writes that observational studies such as these "fall far short of showing a causal effect."
That is, none of the studies prove that fish or omega-3 fatty acids were responsible for the results.
Rosenberg works in Boston at Tufts University's Jean Mayer Human Nutrition Research Center on Aging.