Until a recent Canadian study, conducted at Children’s Hospital in Vancouver, British Columbia (Kiddie, Weiss et al, pre-publication data, 2009), there were only three studies assessing the dietary intake of children with ADHD.

In the first of two studies conducted in the late 1980's (Kaplan, McNicol, Conte, & Moghadam, 1989), preschool ADHD boys did not eat a higher percentage of calories as protein or fat, but they did eat more calories over-all and a higher percentage of calories as carbohydrates than non-ADHD controls. Unfortunately, this early study only involved preschool ADHD boys and one cannot apply this data to ADHD children of other age groups or to both ADHD boys and girls. (Kaplan et al., 1989).

A second study was conducted in South East Asia (Chen, Hsu, Hsu, Hwang, & Yang, 2004).  There was no significant difference in the percentage of calories from protein, fat and carbohydrate between ADHD children and controls, but dietary intake patterns in these children reflect local Taiwanese culture (Chen et al., 2004), and cannot be applied to a North American ADHD population.

A third study conducted in the United States with ADHD children aged 5-10 years of age assessed dietary intakes using an adult food frequency questionnaire (FFQ) adapted for use in children with ADHD. Food frequency questionnaires are known to overestimate dietary intake and no information was given as to how the food frequency questionnaire was adapted for use in ADHD children, or how, or if it was previously validated (Arnold et al., 2005). Since the authors compared mean macronutrient intake (protein, fat, carbohydrate) of the ADHD children to the Recommended Daily Allowances (RDAs) which are used to assess the nutrient intake of individuals, and not groups, it is impossible to comment on the adequacy of dietary intake of the ADHD children from this study.

Only two previous studies have assessed the micronutrient intake (vitamins, minerals) of children with ADHD, and only one of these studies was performed in North America. The first of these studies, mean daily intake of iron (Chen et al., 2004) was significantly above the mean dietary intake of the control group. Mean dietary intake of iron for both the ADHD group and controls was below the US mean dietary intake of children aged 6 - 11 years as assessed by NHANES III  (National Center Health Statistics, 1996c). One can’t compare dietary intake data from Taiwan to a North American ADHD population.

In the second study that assessed micronutrient status, mean dietary iron intake of ADHD children aged 5-10 years of age (Arnold et al., 2005) was above the US mean dietary intake of children aged 6 - 11 years as assessed by NHANES III (National Center Health Statistics, 1996c). Mean dietary intake of the group was well above the mean dietary intake of zinc as assessed by NHANES III (National Center Health Statistics, 1996c) in children aged 6 - 11 years.

There are also several recent studies that indicate low micronutrient status in children with ADHD. Low iron status in children with ADHD was reported in a study from France (Konofal, Lecendreux, Arnulf, & Mouren, 2004) and low iron status was reported in the Taiwanese study (Chen et al., 2004). In the French study (Konofal, Lecendreux, Arnulf, & Mouren, 2004), low serum ferritin levels were correlated with more severe ADHD symptoms, as measured with a Conner’s rating scale. The Taiwanese study (Chen et al., 2004) did not specify whether serum ferritin or serum iron was assessed, so one is not able to compare this data to data from other studies or reference data. Since children in Taiwan eat very differently than children in North America, one cannot compare it to data from North America.

There are several reports of low serum and urinary zinc levels among ADHD children although most data are from the Middle East where the prevalence of zinc deficiency is widespread (Bekaroglu, Aslan, Gedik et al., 1996; Kozielec, Starobat-Hermelin & Kotkowiak, 1994; Starobat-Hermelin, 1998; Toren, Elder, Sela, Wolmer et al, 1996). A recent US study of children aged 5-10 (Arnold et al., 2005) reported that low zinc status in ADHD children was associated with greater parent-teacher ratings of inattention even though all children in the study fell within the normal lab reference range.  That being said, almost a third of ADHD children had serum zinc levels below the population normal reported for children aged 9-11 years (National Centre Health Statistics, 1996).

A recent research study entitled Dietary Intake and Nutrient Status in Children with ADHD (Kiddie, Weiss et al, 2009, pre-publication data) did not support previous findings that ADHD children consumed more overall calories and a higher percentage of calories from carbohydrate (Kaplan et al., 1989). Dietary intake of macronutrients (protein, fat, carbohydrates) by ADHD children was found to be comparable to data from age- and gender-matched children from the normal population (Garriguet, 2004) as well as previous ADHD studies (Arnold et al., 2005).

This study found that a considerable percentage of children in this study were below the EARs (assessor of group adequacy) of both zinc and copper based on age and gender (National Academy Press, 2000). In addition, mean dietary intake of copper and zinc of ADHD children in this study was significantly below age- and gender-matched population normal data (National Center Health Statistics, 1996b). Dietary intake of zinc in children aged 5-10 years in this study was significantly lower than children in the same age range from a previous ADHD study (Arnold et al., 2005). Two-thirds of ADHD children in this study had serum zinc values that were below that of normal, healthy children of comparable age and gender drawn from the same hospital population. In addition, serum copper levels were also significantly below lab normal data and population normal data for children of comparable age and gender (National Center Health Statistics, 1996c).

Striking was that almost a quarter of children in this new study had serum zinc values below the 2.5th percentile cutoffs for zinc deficiency established in the NHANES II population study. For children aged 6 to 8 years, prevalence of serum zinc deficiency was almost 9 times greater than that reported in the general population. Furthermore, prevalence of serum zinc deficiency for children aged 9-12 years was 19 times greater than reported in the general population.