The Effects of Dietary Modification on ADHD: A Concise Review

Inconsistent findings on food colorings and positive findings on highly restrictive diets

Many studies have investigated the effects of changes in diet on symptoms of ADHD. Research findings support that artificial food colorings do not contribute to ADHD however excluding food additives, sugar and certain food groups may reduce symptoms of hyperactivity in some cases.

Early studies on a restrictive diet that eliminates all processed foods reported promising findings in children with ADHD; however, a review of controlled studies failed to support these findings. Early studies suggested that artificial food colorings were associated with ADHD however a meta-analysis failed to confirm this. The oligoantigenic diet (OAD) is a highly restrictive multiple elimination diet that excludes food colorings and additives, in addition to dairy products, sugar, wheat, corn, citrus, eggs, soy, yeast, nuts and chocolate. Oligoantigenic diets permit a limited number of hypoallergenic foods, like lamb, chicken, potatoes, rice, banana, apple, cabbage, broccoli, Brussels sprouts, carrots, peas, pears and cucumber, as well as salt, pepper, calcium, and some vitamins. Studies involve several phases and require many weeks to complete. During phase I, which typically lasts 4 weeks, specific food items are withheld from the diet and the patient is monitored using standardised symptom rating scales. In cases where symptoms improve during the initial treatment phase, specific foods are gradually re-introduced in phase II. A third phase follows a placebo-controlled crossover design in which the patient is randomized to a food item that initially caused symptoms or an acceptable placebo for 1 week, followed by a washout period, and subsequently exposed to either placebo or a specific food item or additive for an additional week. Several studies on the OAD regimen reported significant reductions in hyperactivity in children diagnosed with ADHD when specific food items were eliminated from the diet using the above protocol. In all of these studies behavioral symptoms improved during the elimination and placebo phases and recurred when children were subsequently challenged with the eliminated food item following a blinded protocol. A recent meta-analysis of studies on restrictive diets in childhood ADHD including 14 open studies and six controlled trials concluded that roughly 1/3 of hyperactive children may benefit from some form of an elimination diet.

Large well-designed studies are needed to confirm benefits of dietary modification

Although these results are promising they cannot be used to develop general ADHD treatment protocols because of study design flaws, including heterogeneity of patient populations, absence of standardized outcome measures, high drop-out rates and, in some studies, non-blinded researchers. In the face of these promising findings the American Academy of Pediatrics does not endorse elimination diets because of inconsistent findings of efficacy and concerns that highly restrictive diets do not provide balanced nutrition. Parents who are considering restrictive diets should consult with a nutritionist and highly restrictive diets should not be continued longer than two weeks in the absence of noticeable improvements in ADHD symptoms.

To learn more about the role of nutrition and other non-pharmacologic treatments of ADHD read my e-book “Attention-Deficit Hyperactivity Disorder: The Integrative Mental Health Solution.”

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