How does diet affect behavior?
Nutritional deficiencies and excesses have long been associated with various behavior problems. From time to time, everyone experiences irritability or edginess due to hunger and feelings of drowsiness or lethargy after a large meal. Long-term effects of nutrition on behavior are more difficult to prove. However, some associations are well documented, including:
Learning problems. Malnutrition during infancy has a profound effect on brain development. Autopsies of children who died of malnutrition show decreased brain cells. Malnourished children who survive typically have difficulty learning to speak. Their motor skills lag behind other children, and they have shortened attention spans. In addition, studies of school meal programs have found that children who eat a well-balanced breakfast learn better than those who skip breakfast.
Social problems. Studies have found that malnourished youngsters often have problems getting along with others. Iron deficiency has also been linked to behavior problems in school children. It is unknown, however, whether these problems are due entirely to diet, or whether other factors such as a deprived economic and emotional environment also play a causative role.
In general, however, unfounded claims and beliefs linking diet and behavior outnumber those that have been proven. Some misconceptions relate to:
Criminal behavior. Claims that sugar, food additives, and other dietary components can trigger aggressive or criminal behavior are anecdotal and have never been scientifically proved. Even so, a number of criminals, including a San Francisco murderer, have invoked the so-called Twinkie defense by blaming their actions on junk-food addictions. Similarly, there is no scientific evidence to support claims that food allergies trigger aggressive or criminal behavior.
Childhood hyperactivity. Sugar, food dyes and other additives, and salicylates (an ingredient in aspirin and a number of foods) are among the many dietary substances that have been linked to hyperactive behavior. However, none of these associations have been proved. In fact, research studies at the National Institutes of Health found that sugar either had no effect on childhood
behavior or that it produced drowsiness.
Depression or "sugar blues." Gloria Swanson, the late actress, was one of the leading proponents of the hypothesis that sugar causes depression. Again, there is no scientific evidence to support this claim, which was popularized in a book entitled Sugar Blues.
Irritability in children. Parents sometimes note that certain foods provoke irritability, fussiness, and other symptoms. These symptoms are more likely to be the result of malabsorption, lactose intolerance, or other digestive disorders, rather than to stem from specific food sensitivities.
What can I do myself?
As much as possible, avoid using food to reward or punish behavior. For example, many parents use food to quiet a fussy baby or to end a toddler's temper tantrum. In such situations, a child quickly learns how to use food to get his or her way. In addition, lifelong weight problems can be fostered by using food as a childhood pacifier.
If you are convinced that certain foods provoke outbursts, irritability, anxiety, or other behavioral symptoms, try eliminating them from your diet. After a few weeks, slowly reintroduce them one by one to see if the symptoms recur. A word of caution, however: Be careful not to eliminate entire food groups or to adopt a diet that is so limited that it is likely to lead to nutritional deficiencies.
When should I see my doctor?
Persistent behavior problems should be discussed with your doctor. Some may be due to hormonal imbalances or other organic disorders. Others may require evaluation and treatment by a psychiatrist or psychologist. In children, behavioral changes are often a normal part of development.
If you suspect that a food allergy is related to behavioral problems, talk to your doctor about blinded challenge testing. This entails withholding the suspected food or foods. The person is then given a series of pills, wafers, or drinks. Some contain the suspected substance and others are placebos. Neither the patients nor the person administering the test knows which is which. If the person responds to the suspected substance and not to the others, then he or she may well be allergic to it.
A nutritious, well-balanced diet is essential for all aspects of normal growth and development. It is unlikely, however, that diet alone causes or prevents behavioral problems. Instead, a combination of factors, of which diet is only one of many, shapes a person's behavior.
Parents should strive to instill common-sense eating habits in their children at an early age, preferably by setting good examples themselves. Parents should also resist the temptation to use food to comfort a fussy baby or to reward good behavior — practices that are likely to result in poor eating habits as well as undesirable behavior.
Advice about diet and behavior
- Avoid manipulating a child's diet in an attempt to solve learning or behavior problems. Chances are that diet has little or nothing to do with the problem, and that dietary changes may do more harm than good.
- Do not resort to self-treating hyperactivity and other behavioral or emotional problems with high-dose vitamins and minerals. This potentially dangerous practice is advocated by some practitioners of orthomolecular therapy — an alternative approach to psychiatry that is based on megadose nutritional supplements.