The idea that eating certain “brain foods” such as fish and eggs could make a person smarter has been in existence for centuries. Unlike most miracle-food rumors, these claims have some basis in fact.

Fish, for example, especially salt-water fish, is a good source of iodine. Before iodine was routinely added to salt, many people who lived inland lacked this mineral in their diets. This often caused a condition called goiter, where the thyroid gland enlarges and production of the thyroid hormone, thyroxine, decreases. Thyroxine is necessary for proper mental function. When a person who suffered from iodine deficiency ate fish, the thyroid was stimulated into producing more of the essential hormone. The person usually became alert and able to think clearly.

The idea that eating eggs will make a person smarter also may have slight merit. Egg yolks, as well as liver and legumes, are rich sources of a substance known as lecithin. In the body, lecithin is broken down into its components, one of which is choline. Choline aids in the production of acetylcholine, which helps transport nerve impulses to the brain.

Brain-food diets, however, have become more sophisticated and complicated than merely fish and eggs. Today, several intricate diet plans outline exact amounts of specific foods at particular time of the day, claiming that this eating pattern will increase a child’s IQ by 15 or more points.

The basic principle behind some of these diets is sound. Good nutrition during pregnancy and in the first few years of life will provide a better chance for intelligence in later life. Poor nutrition, after all, can affect all the body’s organs and systems, including the brain and the nervous system. In the fetus, the brain grows the cells in the brain continually divide and increase in number. After the infant is born, brain growth occurs as the cells increase in size as well as numbers. When the infant is approximately 18 months of age, the number of cells in the brain stops increasing, but the existing cells continue to grow in size. Brain cell growth continues until the child is approximately 5 years old.

Severe malnutrition at any time in this developmental process can stunt brain growth. If the fetus and the newborn are not properly nourished, the result may be fewer brain cells. If the child is malnourished between the ages of 18 months and 5 years, the permanent size of the cells in the brain may be smaller than normal. Both of these conditions could result in reduced mental capacity. Good nutrition during Pregnancy and the early years is thus vital.

Proponents of brain-food diets prescribe food plans that are rich in egg yolks, fish, peanut butter, cheese, yogurt, meat, dried beans and other vegetables. Most of these diets are relatively high in fats – up to 50 percent. (Fat is thought to be vital for proper formation of the brain cells and for construction of the protective shields around these cells.) Brain-food diets often prescribe nutrients in roughly the same concentrations that would be found in human breast milk. Besides the 50 percent fats, these diets usually consist of anywhere from 35 to 45 percent complex carbohydrates, and 5 to 15 percent protein. This proportion of fat in the diet of a child older than 6 months can cause later problems with weight and heart disease.

Parents should evaluate these diets the way they would any other food plan. If the specific brain-food menu concentrates too heavily on any particular food or food group, chances are that it is not a suitable program for a growing, developing child.

It should be made clear, however, that there is no evidence to support the claim that adhering faithfully to a brain-food diet while pregnant or placing a child on a brain-food regimen will produce a genius. Mental capacity, after all, is determined by more than diet.