真有能让人变聪明的食物吗？餐桌上，家长总是告诉孩子，吃这个补脑，或者吃那个能让你更聪明，可是真的有哪种食物有这么神奇的功效吗？

    How does food affect mood and mind? The answer may lie in the chemistry of the brain and nervous system. Molecules called neurotransmitters（神经递质）are chemical messengers. They carry a nerve impulse across the gap between nerve cells. The release of neurotransmitter molecules from one neuron and their attachment to receptor sites on another keep a nerve impulse moving.

    Nerve impulses carry messages from the environment to the brain for example, the pain you feel when you stub your toe. They also carry messages in the other direction, from the brain to the muscles. That’s why you back away from the obstacle that initiated the pain signal and exclaim, “Ouch!” 

    “Many neurotransmitters are built from the foods we eat,” says neuroscientist Eric Chudler of the University of Washington. Too little or too much of a particular nutrient in the diet can affect their production, Chudler says. For example, tryptophan（色氨酸）from foods such as yogurt, milk, bananas, and eggs is required for the production of the neurotransmitter serotonin. Phenylalanine from beets, almonds, eggs, meat, and grains goes into making the neurotransmitter dopamine（多巴胺）.

    Dozens of neurotransmitters are known; hundreds may exist. Their effects depend on their amounts and where they work in the brain. The neurotransmitter serotonin, for example, is thought to produce feelings of calmness, relaxation, and contentment. Drugs that prevent its reuptake (into the neuron that released it) are prescribed to treat depression. In at least some healthy, nondepressed people, carbohydrate foods seem to enhance serotonin（复合胺）production and produce similar effects. “It is the balance between different neurotransmitters that helps regulate mood,” Chudler says.

    Proper nutrition may also enhance brainpower. Choline（胆碱）is a substance similar to the B vitamins. It’s found in egg yolks, whole wheat, peanuts, milk, green peas, liver, beans, seafood, and soybeans. The brain uses it to make the neurotransmitter acetylcholine. To test the effects of choline on memory and learning, researchers at the Massachusetts Institute of Technology gave memory tests to college students before increasing the amount of choline in their subjects diets. Later, they retested. On the average, memories were better, and the students learned a list of unrelated words more easily.

    If he were alive today, a smart and happy Hippocrates（希波克拉底，西方医学之父）might be spotted buying skinless turkey at the supermarket or munching broccoli from the salad bar. Who knows what those foods might have done for him. The question is, What can they do for you?