Fat in Fish May Help Prevent Dementia

Nov. 13, 2006 -- Eating fish three times a week may cut your odds of getting dementia almost in half.

That news appears in the November issue of Archives of Neurology.

Researchers base their findings on a study of 900 older men and women. The scientists found that participants with the highest DHA levels at the beginning of the study were 47% less likely to get dementia and 39% less likely to get Alzheimer's disease during the study than the rest of the group.

The researchers included Ernst Schaefer, MD, of the U.S. Department of Agriculture Human Nutrition Research Center, at Tufts University.

DHA is short for the fatty acid docosahexaenoic. It is found in fish such as salmon, sardines, and herring, and appears important in cutting dementia risk, Schaefer's team notes.

The scientists don't promise DHA prevents the condition, calling instead for more studies.

DHA Study

The study looked at about 900 men and women, aged 55 to 88, who did not have dementia at its start.

Participants completed dietary surveys and got their blood DHA levels checked.

They then took mental skills tests every two years and were followed for nine years, on average.

During that time, 99 developed dementia, including 71 who got Alzheimer's disease.

But the participants who had had the highest DHA levels on the earlier tests were much less likely to get either condition. Those with the highest DHA levels reported eating fish three times weekly, on average.

The results take other factors -- including age and education level -- into account.

However, they don't prove DHA prevents dementia. This study was purely observational; the scientists didn't directly test DHA for dementia prevention.

Fish Factor

The study is the "first evidence" of a link between direct measures of human blood DHA levels and lower Alzheimer's disease risk, writes editorialist Martha Clare Morris, ScD.

DHA is abundant in the healthy human brain, notes Morris, who works at Chicago's Rush University Medical Center.

Fish is the main dietary source of DHA, but vegetable oil, soybeans, walnuts, wheat germ, and human milk also contain DHA, Morris notes. It is also available in supplements.

Future studies should check whether such supplements can halt the worsening of established dementia, say the researchers, and Morris agrees supplements deserve further study.