How Fish Fat Fights Alzheimer's

People who eat a lot of omega-3 fatty acids--the famous fat from fish--are less likely to get Alzheimer's disease, but no one knows how the fats protect the brain from damage. A new study with mice, however, provides some intriguing clues.

The omega-3 fatty acid known as docosahexaenoic acid (DHA) abounds in healthy neurons. But in Alzheimer's brains, it appears to get trashed by the amyloid protein that makes up the damaging plaques that characterize the disease. To find out if supplemental DHA could protect the brain from neurodegeneration, neuroscientist Gregory Cole of the University of California, Los Angeles, and colleagues tinkered with the diet of mice that produce a mutant human amyloid protein. These mice accumulate amyloid in the brain and have mild memory problems in old age. When the mice were 18 months old, or middle-aged, the researchers fed them a diet either depleted of, or supplemented with, DHA for 4 months. The team then tested the memory of the mice by requiring them to remember the location of a submerged platform in a pool of water. The mice that had eaten a DHA-poor diet took significantly longer to find the hidden island than those that had chowed DHA. In fact, the mice that ate DHA did just as well as control mice that don't get ravaged by the Alzheimer's protein. Autopsies showed that key proteins needed for learning and memory had disappeared from neurons in amyloid-laden mice that hadn't eaten DHA, the researchers report in the 2 September issue of Neuron. "Alzheimer's disease may create an extra need for [omega-3] fatty acids," says neuroscientist Lennart Mucke of the University of California, San Francisco, who adds that the study provides a plausible explanation for the beneficial effects of omega-3's. He adds that it's too soon to know whether increasing dietary DHA will help ward off Alzheimer's in humans, but "if anyone wants to hedge their bets in the meantime, they can eat more fish."