Eating fish and other foods rich in omega-3 fatty acids could help people maintain healthy brains as they age, as well as protect their hearts, new research suggests.

In a study to be released Tuesday, participants with low levels of omega-3 fatty acids in their blood had slightly smaller brains and scored lower on memory and cognitive tests than people with higher blood levels of omega-3s.

The changes in the brain were equivalent to about two years of normal brain aging, says the study's lead author, Dr. Zaldy Tan, a visiting associate professor in the geriatrics department of the University of California, Los Angeles, and a member of the UCLA Easton Center for Alzheimer's Disease Research. Brains normally shrink as people age.

The study involved 1,575 people with an average age of 67 who didn't have dementia, a condition typically marked by memory loss. The study was part of the larger, federally funded Framingham Heart Study, which is looking at what contributes to cardiovascular disease. The study will appear in the journal Neurology.

Several studies have shown diets that include fish, such as the Mediterranean diet, lower people's risks of developing heart problems or having a stroke. And some studies, including one of the first set of participants in the ongoing Framingham study, which started in 1948, suggested intake of fatty fish like salmon and tuna can lower the risk of Alzheimer's disease and other causes of dementia.