How to Eat Smart

What you eat affects your brain. While the foods we eat have measurable effects on the body's performance, they may prove to have an even more critical influence on how the brain handles its tasks.

By Randy Blaun, Andreas Wiesenack, published on May 01, 1996 - last reviewed on October 01, 2009

When you eat a protein-rich meal, Wurtman explains, the protein is broken down into component amino acids, some of which, like tryptophan, are neurotransmitter precursors. All of them, however, must compete to get into the brain. But when you eat a meal or snack that's mainly carbohydrates—provided it supplies less than five percent of calories from protein—insulin rushes in and, while targeted at the carbs, also sweeps up any amino acids lingering in your bloodstream from a previous protein meal. All the amino acids, that is, but tryptophan. Survivor of the insulin onslaught, tryptophan slips into the brain uncontested. Once there, it is converted to serotonin and elevates mood.

Wurtman, author of The Serotonin Solution (Ballantine, 1996), has found that women with premenstrual syndrome (PMS) dramatically increase their carbohydrate intake in the two weeks prior to menstruation, while women not subject to PMS do not. She sees this as evidence of self-medication, an attempt to increase brain levels of serotonin in order to alleviate the anxiety, depression, and concentration difficulties that characterize PMS. Ditto individuals who develop depression and fatigue in the winter months, who increase carbohydrate intake seasonally.

Carbohydrates may be calming for another reason, suggests Barbara Smith, Ph.D., assistant professor of psychology at Johns Hopkins University. Her studies indicate that the sweet taste of sugar stimulates the release of endorphins, the brain's natural opiates. Either or both effects may account for the results seen in a study, conducted at the University of Wisconsin, of delinquent adolescent males. When subjects were fed a breakfast of cereal high in sugar, researchers documented an improvement in depressive symptoms and fewer incidents of aggressive behavior.

The Busy Bs

The B vitamins consist of thiamin (B1), riboflavin (B2), niacin, pyridoxine (B6), folic acid, pantothenic acid, biotin, and cobalamin (B12). All play a critical role in brain function, from manufacturing neurotransmitters to regulating energy release in brain cells.

Severe deficiencies of several B vitamins have been shown to have profound effects on the brain, leading to abnormal brain waves, detectable as abnormalities on EEGs; impaired memory; and higher levels of anxiety, confusion, irritability, and depression. Even marginal deficiencies of B vitamins can cause EEG disturbances and inhibit mental performance, reports James G. Penland, Ph.D., a research psychologist at the U.S. Department of Agriculture's Human Nutrition Research Center in Grand Forks, North Dakota. Although many of the studies were done on older people, who are frequently deficient in vitamins and minerals, the same impairments could be expected in younger people with the same marginal deficiencies.

At the University of California San Diego Medical School, where he is professor of psychology, Philip Langlais, Ph.D., finds that thiamin deficiency hampers the brain's ability to use glucose, decreasing energy available for mental activities. It also overexcites neurons so that they fire endlessly, poop out, and die. "If you are even marginally deficient in thiamin," says Langlais, "you may be slowing down your brain power."

Folic acid, meanwhile, helps maintain normal levels of serotonin. Deficiencies contribute to depression, dementia, and schizophrenia. In a study of depressed patients taking lithium, those also given folic acid supplements for a year showed dramatic relief of depression, compared to those given no supplements.

Oh Those RDAs

Americans, it's clear, are not malnourished calorically; in fact we consume too many calories. So it is indeed ironic that in the land of plenty we may be undernourishing our brains. According to Penland, Americans' eating patterns, and especially those of women, as a result of dieting, serve up special shortages of folic acid and minerals, including iron, calcium, magnesium, manganese, copper, and selenium. While men eat more calories than women do, that doesn't give them better brains. Studies show that they eat fewer vegetables, fruits, grains, and nuts, foods rich in key vitamins and minerals.

But even consuming recommended dietary allowances (RDAs) for all nutrients may hot guarantee a robust brain. The current RDAs, says Penland, are crude measures, based on a few animal studies and on observations of what people ordinarily consume, and these allowed experts to decree minimum levels of vitamins and minerals needed to sustain normal growth, maintain immune function, and fend off death, plus a safety margin to accommodate individual differences. But nutrient levels needed for optimal general health and brain functioning may be many times higher than current RDAs, as they were in many of his own studies, says Penland.

Still, it would not be prudent to wolf down mega-amounts of vitamins and minerals. Reliable studies of the long-term effects of megadoses have yet to be done, especially of trace minerals, which can be toxic in large amounts. Penland warns against taking doses that exceed the RDAs at this time, except for calcium, the RDA that is widely considered too low for most women. But along with other experts interviewed for this article, he suggests that, on top of a healthful diet, you take a multivitamin and mineral supplement that supplies RDA amounts. This is particularly important for the elderly, among whom marginal deficiencies of vitamins and minerals are widespread.