Fast foods, sodas, and ice cream may be American kids' favorite menu items, but they're also probably the worst for those with attention deficit-hyperactivity disorder (ADHD), a new literature review suggests.
According to two researchers from Children's Memorial Hospital in Chicago, a relatively simple diet low in fats and high in whole grains, fruits, and vegetables is one of the best alternatives to drug therapy for ADHD. Omega-3 and omega-6 fatty acid supplements have also been shown to help in some controlled studies, they noted.
Writing online in Pediatrics, Dr. J. Gordon Millichap and Michelle M. Yee reviewed nearly 70 publications on diet-based interventions in ADHD, emphasizing recent research and controlled trials.
They noted that diet is one established contributor to ADHD that parents can modify.
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One of the most provocative findings in recent years came from the Australian Raine study, which was a prospective cohort study that followed children from birth to age 14, Millichap and Yee indicated.
It found that development of ADHD was significantly associated with so-called Western diets rich in saturated fats and sugar, compared with a "healthy" diet of proteins derived from low-fat fish and dairy products and with a high proportion of vegetables (including tomatoes), fruits, and whole grains.
However, their review indicated that controlled trials had failed to show significant benefits for such intensive modifications as oligoantigenic, elimination, or additive-free Feingold-type diets except in small subgroups. Such diets also "are complicated, disruptive to the household, and often impractical," they wrote.
The Feingold diet and others are based on the idea that artificial colors and salicylates contribute to ADHD, which became popular in the 1970s. Federally funded trials showed that most ADHD children did not improve significantly on such diets, although some children with genuine sensitivities to additives and preservatives have been identified.
Such children, the researchers suggested, "might benefit from their elimination." More recent research has also indicated that atopic children with ADHD responded to a highly restrictive diet lacking colorings, preservatives, and certain food types.
Millichap and Yee reached similar conclusions for so-called elimination diets that avoid common allergens such as nuts, dairy, and chocolate, as well as citrus fruits. "Studies have provided mixed opinions of efficacy," they noted.
For both types of diet, the researchers pointed out, "a parent wishing to follow [them] needs patience, perseverance, and frequent evaluation by an understanding physician and dietitian."
In another finding likely to raise eyebrows, if not hackles, Millichap and Yee concluded that only weak evidence supports the widespread belief that refined sugar promotes hyperactivity.
Some effects on brain electrical activity have been documented, and reactive hypoglycemia following big jolts of sugary foods may account for behavioral changes seen in some ADHD children.
But studies linking sugar consumption to ADHD have also been compromised by methodological problems. For example, one trial gave children sugar or placebo at breakfast with a high-carbohydrate cereal, which may have contributed to subsequent reactions to the sugar. Millichap and Yee cited a separate study that demonstrated when children ate a protein meal before or simultaneously with sugar, no hyperactivity reaction occurred.
Still, the researchers conceded, the notion that sugar exacerbates ADHD has become so entrenched it may not matter whether it's true or not.
"No controlled study or physician counsel is likely to change this perception. Parents will continue to restrict the allowance of candy for their hyperactive child at Halloween in the belief that this will curb the level of exuberant activity, an example of the Hawthorne effect. The specific type of therapy or discipline may be less important than the attention provided by the treatment," Millichap and Yee wrote.
They also reviewed studies exploring the potential roles of zinc and iron deficiency in ADHD. The upshot is that there is currently little indication that such deficiencies explain more than a small minority of ADHD cases. Children with confirmed deficiencies should receive supplements or appropriate dietary adjustments regardless of their ADHD status.
They were more impressed with the literature on polyunsaturated fatty acid supplements, especially the 2005 Oxford-Durham study.
In that trial, several ADHD symptoms were significantly improved in children receiving omega-3 and omega-6 fatty acid supplements, "an effect duplicated in other...supplement trials," Millichap and Yee wrote.
They acknowledged that not all studies have confirmed the result, and recent studies have used too many different methodologies to yield firm conclusions. Nevertheless, they indicated that they now recommend it to parents of their patients, though not as the sole treatment approach.
"In almost all cases, for treatment to be managed effectively, medication is also required," they wrote. "The beneficial effects of omega-3 and omega-6 supplements are not clearly demonstrated."
"Supplemental diet therapy is simple, relatively inexpensive, and more acceptable to patient and parent," Millichap and Yee concluded. "Public education regarding a healthy diet pattern and lifestyle to prevent or control ADHD may have greater long-term success."
They suggested that diet-based interventions in ADHD are most appropriate when children suffer medication reactions or treatment failure, parents or children want to try dietary modifications or mineral deficiencies are evident.