Fish on the brain: Can eating it keep Alzheimer's at bay?

• Shrinking brain volume is a sign of normal aging
• Women with higher levels of omega-3 fatty acids had slightly larger brain volume
• Those women also had a larger volume in the hippocampus portion of the brain

A diet rich in fish has been touted as a way to improve brain health, but research results on its effectiveness have been mixed.

A study out Wednesday found older women with the highest levels of omega-3 fatty acids, found in fish oil, had better preservation of their brain as they aged than those with the lowest levels, which might mean they would maintain better brain function for an extra year or two.

The results suggest that higher omega-3 fatty acid levels may hold promise for delaying cognitive aging and dementia, says the study's lead author, Jay Pottala of the University of South Dakota in Sioux Falls and Health Diagnostic Laboratory in Richmond, Va., which offers blood testing including for omega-3 fatty acids.

Fish high in omega-3 fatty acids include salmon, herring, tuna, mackerel, sardines and swordfish.

For the latest study, Pottala and colleagues looked at the omega-3 fatty acids levels in the red blood cells of 1,111 women who participated in the Women's Health Initiative Memory Study. The women had MRI scans eight years after the study began to measure their brain volume. They were an average of 78 years old. The study was supported by the National Heart, Lung and Blood Institute.

Findings published Wednesday online in Neurology, the journal of the American Academy of Neurology:

-- Those with the highest levels of omega-3 fatty acids in their red blood cells had a 2.7% larger volume in the hippocampus portion of the brain compared with those with the lowest levels of omega-3 fatty acids. The hippocampus plays an important role in memory and is usually one of the areas affected early in the dementia process, Pottala says.

-- Those with the highest levels of omega-3 fatty acids in their blood had 0.7% larger overall brain volume compared with those with the lowest levels.

Shrinking brain volume is a part of aging, he says. "This doesn't mean their brains got bigger; it just means their brains didn't atrophy as much."

These benefits could be achieved with fish or fish oil supplements, Pottala says. To get to a high enough level, you would have to eat oily fish at least twice a week and take fish oil supplements daily or eat fish at least five times a week, he says.

Pottala was one of the researchers on the study released this fall that didn't find a benefit to omega-3 fatty acid levels and better memory and thinking skills for older women, but he says the women may have been too healthy for any short-term benefits to show.

Ronald Petersen, director of the Mayo Clinic Alzheimer's Disease Research Center, says there have been conflicting reports on this topic but this latest research "would suggest there is a positive relationship between omega-3 fatty acid-rich diets and the preservation of brain volume in aging. The take-home message is to eat a heart-healthy diet that includes fish. I'd also recommend physical exercise and engagement in intellectual activity."

Overall healthy living is beneficial to healthy brain aging, adds Heather Snyder, director of medical and scientific relations for the Alzheimer's Association. "The strongest evidence we see in the research is the benefit of physical activity for potentially reducing the risk of Alzheimer's disease."