Diet and Its Possible Role in Developmental Disorders

As early as 1922 dietary factors have been suspected of exacerbating, if not causing, cognitive and behavior problems among some individuals with developmental disorders (Shannon, 1922, as cited by Atkins, 1986). Although any such association has often been dismissed based on early studies of children with hyperactivity, the hypothesis continues to be discussed and retested. Many parents consult health professionals in complementary or alternative medicine (e.g., Simpson & Roman, 2001) particularly if their children are diagnosed with attention deficit hyperactivity disorder (Bussing, Zima, Gary, & Garvan, 2002). The most common alternative therapy suggested for ADHD involves changes in diet (Stubberfield, Wray, & Parry, 1999). Dietary factors have also been associated with autism and Down syndrome (e.g., Horvath, Papadimitriou, Rabsztyn, et al., 1999; Reading, 1984). Thus, it seems imperative that professionals (both researchers and clinicians) interested in developmental disorders consider the more recent research and revisit the question of the possible role of diet in developmental disorders. If sufficient anecdotal, epidemiological and/or physiological evidence suggest the area is worth continued pursuit, then we should support further research in the area.

In this paper we will consider some of background necessary for understanding the hypotheses about the relation of diet to learning and behavior and we will review some of the literature that tests hypotheses about diet in relation to developmental disorders. The hypotheses we will consider include:

These hypotheses are discussed below along with some background material. It is assumed that the reader is familiar with the symptoms of the various developmental disorders but not as familiar with material on dietary factors.

OUTLINE WITH LINKS TO SECTIONS:

I. INTRODUCTION AND HYPOTHESES
II. DIETARY FACTORS AFFECTING LEARNING AND BEHAVIOR: II.a INSUFFICIENT SUPPLY; II.b INSUFFICIENT NUTRIENTS; II.c OTHER
III. NEUROTRANSMITTERS: III.a TYPES; III.b DIETARY INFLUENCES; III.c DEVELOPMENTAL DISORDERS
IV. DIGESTION: IV.a INTRODUCTION; IV.b DEVELOPMENTAL DISORDERS
V. ADVERSE REACTIONS TO FOOD: V.a ALLERGIES; V.b OTHER ADVERSE REACTIONS
VI. SUGAR: VI.a INTRODUCTION; VI.b DEVELOPMENTAL DISORDERS
VII. FOOD ADDITIVES: VII.a INTRODUCTION; VII.b DEVELOPMENTAL DISORDERS
VIII. PROTEINS: VIII.a INTRODUCTION; VIII.b DAIRY; VIII.c GRAINS; VIII.d DEVELOPMENTAL DISORDERS
IX. SUMMARY RE HYPOTHESES.

IX. SUMMARY RE HYPOTHESES

Most of the hypotheses that were presented at the beginning of this paper have received some support. As stated in Hypotheses A, there is support for the hypothesis that diet can affect learning and behavior. Moreover, digestive disorders are frequently reported among children with developmental disorders, particularly among those exhibiting behaviors within the autistic spectrum (Hypothesis B). However, the relation between these digestive disorders and behavior and learning is less clear. Little support was found for a relation between behavior and sensitivity to sugar (Hypothesis C1). However, there was support for the hypothesis that certain food additives and particular foods may, indeed, have a potential role in developmental disorders (i.e., Hypothesis C2). It appears that some children diagnosed as ADHD are sensitive to particular foods or food additives and that this sensitivity can affect their learning and behavior. Moreover, when offending substances are removed from the diet of such children, positive changes are reported in behavior and mental processing (i.e., Hypothesis D). Although the number of children so affected seems to be small, the benefit of identifying such children and removing offending food substances from their diet appears worth the effort of finding them and attempting dietary intervention. For children whose behaviors fall within the autistic spectrum, the problem foods appear more likely to be proteins from grain and dairy products (Hypothesis C3). Unfortunately, it is less clear that dietary intervention (Hypothesis D) with these children makes a lasting difference in behaviors.

In summary, we found support for the role of diet in affecting learning and behavior in general and for the co-occurrence of digestive problems and some developmental disorders. Sensitivity to food additives is well documented among some children with ADHD and dietary elimination of offending foods appears to be helpful in affecting the behavior of such children. Sensitivity to particular proteins such as gluten and casein is documented for some children with autism. Although the elimination of these proteins from the diet of such children appears logical and is supported anecdotally, the success of dietary elimination is not well documented.

Again, we are struck with the variability among children with developmental disorders and the complexities of the human body. After reading the literature, we do not feel the role of diet in developmental disorders should be dismissed. However, it seems clear that its role is most likely relevant for only subgroups of such children. As is the case with most hypotheses about developmental disorders, more rigorous research is needed. The relationship between sensitivity to particular foods and developmental disorders may lead to other ways of understanding developmental disorders rather than to direct intervention regarding diet. For example, sensitivity to particular foods may be a part of a general immune system dysfunction that is related to developmental disorders.

ACKNOWLEDGMENTS

We thank Amanda L. Lewis for help in collecting references for this paper as well as Henry Lahey, Ph.D. and Fred Pescatore, M.D.for their comments and suggestions on early drafts. We also acknowledge the importance of PubMed, as a source for finding research articles, and the cooperation of MAHEC in Asheville, NC for helping us obtain copies of many of the articles.

[1] This paper was sponsored by the Bamford-Lahey Children's Foundation and is available on their website (Bamford-Lahey.org).[2] Margaret Lahey, Ed.D., President of the Bamford-Lahey Children's Foundation, can be contacted at Bamford-Lahey Children's Foundation, 2995 Woodside Road #400, Woodside, CA 94062.