Older adults in developing countries who regularly eat fish seem to have a lower risk of dementia, a new study suggests.

Researchers found that among nearly 15,000 older adults living in China, India or one of five Latin American countries, the odds of having dementia generally declined as fish consumption rose.

For each increase in participants' reported fish intake -- from never, to some days of the week, to most or all days of the week -- the prevalence of dementia dipped by 19 percent.

The findings, published in the American Journal of Clinical Nutrition, mirror evidence from some studies in developed nations.

The findings also suggest that the fish-dementia link does not simply reflect the benefits of a generally higher-quality diet. The study found that adults who got the most meat in their diets tended to have a somewhat higher prevalence of dementia than those who never ate meat.

The findings are based on a one-time survey and do not prove cause-and- effect, note the researchers, led by Dr. Emiliano Albanese of King's College London in the UK.

More substantive evidence, they write, will come from the next phase of the research, which is following these older adults over time to see whether fish intake is related to the risk of developing dementia in the future.

If fish does protect the aging brain, researchers believe that the benefits probably come from the omega-3 fatty acids found most abundantly in oily fish like salmon, mackerel and albacore tuna.

Lab studies show that omega-3 fats have a number of properties that could help stave off dementia -- including actions that protect nerve cells, limit inflammation and help prevent the build-up of the amyloid proteins seen in the brains of Alzheimer's patients.

These latest findings are based on surveys of 14,960 adults age 65 or older living in China, India, Cuba, the Dominican Republic, Mexico, Peru or Venezuela. The relationship between higher fish intake and lower dementia prevalence was consistent across all countries, with the exception of India.

The link also held when the researchers factored in participants' incomes, education and lifestyle habits like smoking and fruit and vegetable intake -- suggesting that differences in socioeconomics do not fully account for the finding.

SOURCE: American Journal of Clinical Nutrition, August 2009.

United kingdom China India Medicine