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Brain Boost: The Tuna Sandwich

Fish can stop dementia in its tracks—even in those who may be genetically predisposed to Alzheimer's disease.

It sounds like a bad joke. Take two sardines and call me in the morning.

But a team of California researchers has found that a diet rich in fatty oils from cold-water fish can halt the progression of dementia—even in those who may be genetically predisposed to Alzheimer's disease.

The good news, says UCLA neuroscientist Greg M. Cole, is that "we can buy the therapy at a supermarket or drug store." His study showed that animals fed a diet enriched with DHA, or docosahexanenoic acid, an omega-3 fatty acid found in relatively high concentrations in salmon, mackerel and sardines, dramatically cut the harmful brain plaque that marks Alzheimer's disease and appears to precipitate memory decline.

At a time when we've become so fat-phobic, it's important to remember that some fats are beneficial. DHA helps maintain the flexibility of cell membranes, which facilitate communication between brain and nerve cells. Experts say that 60% of the brain is made up of fat, 25% of which is DHA.

High levels of DHA in the brain are associated with an optimal brain function along a number of fronts—from mental sharpness to memory to mood regulation—while low levels have been linked to Alzheimer's disease, attention deficit disorders and depression. Studies show that in cultures where people consume more fish, there are fewer cases of depression.

The lining of every brain cell is made of fat and fatty acids, and a good chunk of the fatty acids are DHA. If we fail to consume enough DHA in our diet, the body substitutes other fatty acids, like saturated or monounsaturated fatty acids. As a result, receptors on cell membranes don't work efficiently, and nerve cells don't communicate well.

Cole has found that DHA protects against damage in the parts of brain cells where they communicate with each other. As a result, animals given extra helpings of the fatty acid perform better on memory tests.

The problem is, the American diet is typically low in omega-3 fatty acids. Since the body does not produce omega-3 essential fatty acids, they must be consumed, either in foods or supplements. Good DHA intake starts at birth, as it is abundant in breast milk and essential for the developing brain and for the eyes. You'll find DHA most abundant in cold-water fish but also in walnuts, flaxseed oil and in fish oil supplements.

DHA also appears to protect against heart disease, lowering levels of triglycerides, blood fats have been linked to heart disease. And it's essential for maintenance of good vision—research found that people who ate more fish had fewer incidences of age-related macular degeneration, which is the leading cause of blindness in older people.

How much omega-3 fat is enough? The American Heart Association recommends at least two servings of fish per week to get cardiovascular benefits. A three-ounce serving of farmed Atlantic salmon has about 1,500 mg of omega-3 fat.