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Is Fish Really Brain Food?

Some of Grandma's health advice (wet feet cause colds, for instance) has not panned out. Some has stood the test of time (such as the idea that roughage—that is, fiber—is good for you). Fish as brain food may also get the nod from scientists. It has already gotten the nod for its cardiovascular benefits. There's now evidence that eating fish can play a positive role in mental health.

It may sound like a joke, but the brain is largely composed of fat. Fats, along with water, are the chief components of brain cell membranes and the specialized tissues enclosing the nerves. The anti-fat message promoted as part of heart-healthy diets these days makes it easy to forget that not all fats are "bad," and that some types are essential to human life.

The saturated fat that comes primarily from meat and full-fat dairy products is not what the brain cells need. They do need polyunsaturated fats, especially the long-chain omega-3 fatty acids found in fish, which are called eicosapentenoic acid (EPA) and docosahexenoic acid (DHA). Fish get them from the algae they eat. (Some leafy green vegetables, as well as walnuts, flaxseed, and canola oil, contain shorter-chain omega-3s; these are not readily converted by our bodies into EPA and DHA.)

Fish linked to a healthy outlook

Surveys suggest that groups with the highest fish consumption have the lowest rates of depression. The Japanese eat the most fish and have the lowest rates of depression in the world. Studies in Finland also suggest that those who eat a lot of fish are less likely to be depressed or think of suicide. But all of these are just associations. There's no proof of a cause-and-effect relationship.

There are plenty of theories afloat as to why fish consumption might allay depression. Dr. Andrew Stoll's bestselling new book, The Omega-3 Connection, suggests that since omega-3s play an important role in brain chemistry, a shortage of them may contri-bute to certain psychiatric illnesses. He also discusses the theory that inflammation in the brain plays a large role in depression, and notes that omega-3s have anti-inflammatory effects. He points out that omega-3 consumption in this country has fallen in the past century, as people have consumed more highly processed foods, while rates of depressive illness have soared. But this is all highly theoretical and open to question. There could be dozens of ways to explain the rise in depressive illness (if indeed there has been a rise), including better diagnosis.

Some interesting preliminary studies do suggest that fish oil, usually in the form of supplements because they are easy to use in research, may be of some help in treating bipolar disorder (also known as manic depression) and schizophrenia. The studies—including one by Dr. Stoll—were small and of short duration, so little can be concluded from them. Scientists are also looking into the possibility that omega-3s can improve function of the aging brain. Fish consumption seems to go along with higher levels of mental functioning among the elderly. But all this research is in its preliminary stages. And, of course, it is possible to function at a high mental level and never eat any fish at all.

The bottom line: We really don't know yet if Grandma was right about fish and the brain. We go along wholeheartedly with the recommendation to get omega-3s from fish. Fatty fish (such as salmon, herring, and mackerel) is definitely good for your heart. Omega-3s cut the risk of blood clots and thus lessen the chance of a heart attack. The American Heart Association now recommends that you eat two servings or more of fish a week. A diet that benefits your heart is likely to benefit your brain as well.

Words to the wise about fish-oil supplements: We don't recommend them. They can have adverse effects: nausea, diarrhea, belching. In people with uncontrolled hypertension or those taking anticoagulants, high doses of fish oil may increase the risk of stroke. Fish oil in liquid or capsule form may contain contaminants, too. Omega-3s are like many other nutrients: more isn't necessarily better. However, people with psychiatric disorders such as manic depression might discuss the possible benefits of fish oil capsules with their doctors.

UC Berkeley Wellness Letter, October 2001