Fish may help to protect the brain against the memory loss and cell damage caused by Alzheimer's disease, scientists reported.

A study of mice carrying a human gene that causes Alzheimer's suggests that a diet rich in an omega-3 fatty acid called DHA slows progression of the disorder in its later stages.

"This is the first proof that our diets affect how our brain cells communicate with each other under the duress of Alzheimer's," said Greg Cole of the University of California, Los Angeles, the senior author of the paper in the journal Neuron. "A diet rich in DHA, or docosahexaenoic acid, dramatically reduces the impact of the Alzheimer's gene.

"Consuming more DHA is something the average person can easily control. Anyone can buy DHA in its purified form, fish-oil capsules, high-fat fish or DHA-supplemented eggs."

In the study, his team focused on Alzheimer's damage to synapses -- the chemical connections between brain cells that facilitate memory and learning. The team bred mice with genetic mutations that cause brain lesions linked to advanced Alzheimer's disease. However, though the mice developed the lesions, they showed little memory loss or synaptic brain damage.

"The mice lived on a nutritious diet of fish, which is chock-full of omega-3 fatty acids," said co-author Sally Frautschy. "We realized that the mice's diet could be countering the very thing we were trying to accomplish -- showing the progression of the Alzheimer's-related brain damage."

Subsequent studies found high amounts of synaptic damage in the brains of the Alzheimer's-diseased mice that ate a DHA-depleted diet. "After adjusting for all variables, DHA was the only factor remaining that protected the mice against the damage," said Cole.

The human brain absorbs DHA rapidly, making a constant supply critical for proper cognitive function, eye development and mental tasks. Sources of DHA include salmon, halibut, mackerel, sardines and herring.