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United States Department of Agriculture

Agricultural Research Service

Wish We Knew More, But We Don't
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James G. Penland

We know that a complete and balanced diet promotes physical health and performance. It seems reasonable therefore to assume that what we eat can also affect mental performance--our abilities to pay attention, to remember things, to make decisions--and how we feel. I believe there is a relationship between nutrition and behavior. But contrary to the impression given by stories in the popular press and promotions by health food and dietary supplement manufacturers, there are few scientifically sound studies to support recommendations to alter our diet to improve how we think and feel. Studies that lack important experimental controls have been widely reported, leaving the public with the impression that we know more than we really do about the relationship between nutrition and behavior.

Early research established that children suffering gross deficiencies in protein and energy experience many delays in mental, behavioral and social development. Severe iodine deficiency in children was identified as the cause of mental retardation (Cretinism), although there is little evidence that supplementation of individuals already consuming adequate dietary iodine will improve mental performance.

A convincing series of studies have shown that adequate iron intakes are necessary for normal activity levels and attention. And recent research suggests that diet, and especially essential minerals, may also effect other behaviors. For example, boron may be important for memory and motor function in the elderly; calcium and selenium may benefit mood; copper and iron may be important for restful, uninterrupted sleep; magnesium may help alleviate mental confusion and motor problems in the elderly; and zinc, critical for growth in developing children and adolescents, may improve memory, reasoning and motor skills. Although exciting, these findings are only preliminary and should not be used to justify altering our diet.

In recent years, research has suggested that dietary needs may change as people face physical and emotional stressors, such as our recent flood and the resulting disruption of our normal daily routines. Natural disasters inevitably result in feelings of confusion, depression and anger, and cause us to experience difficulty paying attention, remembering things and making decisions. It is likely, although again not scientifically established, that our ability to deal with these challenges may be affected by our diet. But specific recommendations simply cannot be made at the present time.

The best advice for those interested in ensuring that their mental performance and mood state are at their peak is to get plenty of exercise, adequate sleep, take frequent breaks to recharge their psychological batteries, and to eat a wide variety of foods to provide needed essential minerals.

Last Modified: 4/4/2007
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