A new study suggests that eating foods that contain omega-3 fatty acids, such as fish, chicken, salad dressing and nuts, may be associated with lower blood levels of a protein related to Alzheimer's disease and memory problems. The research is published in the May 2, 2012, online issue of Neurology®, the medical journal of the American Academy of Neurology.

"While it's not easy to measure the level of beta-amyloid deposits in the brain in this type of study, it is relatively easy to measure the levels of beta-amyloid in the blood, which, to a certain degree, relates to the level in the brain," said study author Nikolaos Scarmeas, MD, MS, with Columbia University Medical Center in New York and a member of the American Academy of Neurology.

For the study, 1,219 people older than age 65, free of dementia, provided information about their diet for an average of 1.2 years before their blood was tested for the beta-amyloid. Researchers looked specifically at 10 nutrients, including saturated fatty acids, omega-3 and omega-6 polyunsaturated fatty acids, mono-unsaturated fatty acid, vitamin E, vitamin C, beta-carotene, vitamin B12, folate and vitamin D.

The study found that the more omega-3 fatty acids a person took in, the lower their blood beta-amyloid levels. Consuming one gram of omega-3 per day (equal to approximately half a fillet of salmon per week) more than the average omega-3 consumed by people in the study is associated with 20 to 30 percent lower blood beta-amyloid levels.

Other nutrients were not associated with plasma beta-amyloid levels. The results stayed the same after adjusting for age, education, gender, ethnicity, amount of calories consumed and whether a participant had the APOE gene, a risk factor for Alzheimer's disease.

"Determining through further research whether omega-3 fatty acids or other nutrients relate to spinal fluid or brain beta-amyloid levels or levels of other Alzheimer's disease related proteins can strengthen our confidence on beneficial effects of parts of our diet in preventing dementia," said Scarmeas.

The study was supported by the National Institute on Aging.