Malnutrition

For proper function, the body must have the correct amount of food, including glucose, vitamins, minerals, and other essential chemicals. For example, the fuel the brain uses is glucose, which is produced from eating carbohydrates or other foods that can be converted to glucose. To grow new connections or add myelin, a fatty sheath to axons, the brain must manufacture the right proteins and fats. It does this by digesting proteins and fats in food and using the resulting amino acids and fatty acids to make the new brain proteins and fats. Without the correct amount and balance of particular building blocks, the brain will not work properly. Too little or too much of the necessary nutrient can affect the nervous system.

Vitamin and mineral deficiencies can be caused by:

• starvation
• poor diet
• poor absorption of vitamins and minerals
• damage to the digestive system
• infection
• alcoholism

The brain of a human fetus grows rapidly from the 10th to 18th week of pregnancy, so it is important for the mother to eat nutritious foods during this time.

The brain also grows rapidly just before and for about two years after birth. Malnutrition during these periods of rapid brain growth may have devastating effects on the nervous system and can affect not only neurons but also glial cell development and growth, which can affect myelin development. Babies born to mothers who had poor diets may have some form of mental retardation or behavioral problems, and children who do not eat well in their first few years of life may develop problems later. Often the effects of malnutrition and environmental problems, such as emotional and physical abuse, can combine to create behavioral problems. Therefore, the exact causes of behavioral disorders are difficult to determine.

Some effects of malnutrition can be repaired by a proper diet, so not all of the effects of poor diets are permanent. Researchers believe that the timing of malnutrition is an important factor in determining whether problems will occur. This means that missing out on a particular nutrient at the time when a part of the brain is growing and needs that nutrient will cause a specific problem there.

Scientists have just begun to understand how changes in particular nutrients alter the brain and how these neural changes then affect intelligence, mood, and the way people act. Experiments that investigate this nutrition-brain-behavior interaction, particularly those that study the effects of malnutrition, are difficult for several reasons. First, there is a link between poor nutrition and environmental factors, so that changes in behavior may not be due to poor nutrition only but to factors such as education, social, or family problems.

Because it is hard to alter only one substance in the human diet, it can be difficult to determine if a particular vitamin or mineral has a certain effect on behavior. For ethical reasons, experiments in which a person is not allowed to eat a particular nutrient cannot be done, so much of the data come from animal experiments. Studies in humans are generally limited to examining the effects of famine and starvation, situations where many nutrients are missing.

Children respond to different diets in different ways. In other words, there is a large individual variation in the body’s response and need for different nutrients. A change in diet may have a placebo effect. The placebo effect occurs because a person thinks something will have an effect. In other words, if a person thinks a change in diet will affect behavior, it may actually affect behavior even if the nutrients are not causing the change. Therefore, experiments must have a placebo control and be performed in a double-blind manner where neither the experimental subject nor the experimenter knows who has received an altered diet.