In children, there is an increasing frequency of the diagnosis of ADHD, a condition characterized by inattention, impulsive and disruptive behavior, learning difficulties, and increased levels of gross motor activity and fidgeting. Also, the prevalence of food allergies and intolerances has been increasing. Perhaps it is not surprising that dietary explanations and treatments for ADHD have been sought regularly for several decades, given theories of allergic reactions or intolerance to food additives, ingredients in chocolate, and even refined sugar (often grouped as the 'Feingold theory', after an early instigator of unproven dietary intervention). There has also been a long-standing interest in the possibility that antisocial behavior in children and adults might in part result from poor nutrition, although early studies were poorly designed. Behavioral effects of sugar and of many additives have by and large not been supported by controlled studies; however, determining unequivocally whether the behavior of young children is affected by specific dietary components is difficult. ADHD may be associated with disrupted eating behavior and poor nutrition, so that removal of a number of nutrient deficiencies might improve behavior. In addition, parents or unqualified health professionals may devise unsuitable dietary regimes that can increase the risk of undernutrition. As a result, there is little consensus as to what in the diet may or may not provoke disturbed behavior in children, other than that only a small minority of children are likely to be affected. Nevertheless, a recent British study, in which children were given a collection of food colorings and preservatives, or a placebo, in drinks, found a deterioration in the behavior reported by parents for both hyperactive and normal children given the additives, which seemed unrelated to allergic history. This effect was not detectable in a clinical setting. Clearly, a definitive answer will require more research.
Nevertheless, one promising line of research has involved supplementation with n-3 and n-6 highly unsaturated essential fatty acids: a recent study of ADHD children found improvement in the supplemented group on several behavioral measures after 3 months. Furthermore, a recent randomized placebo-controlled trial of dietary supplementation in young adult prisoners in the UK found a substantial reduction in antisocial behavior. The supplement used was a multivitamin and mineral preparation taken together with a combined n-3 and n-6 fatty-acid supplement, for a period varying from 2 weeks to 9 months. Other effects of essential fatty acids on cognition are discussed below.
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