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The Role of Diet and Nutrition in Attention-Deficit/Hyperactivity Disorder
By Richard G. Petty, MD, Dr. Petty is Scientific Director, Promedica Research Center, Loganville, GA, and Adjunct Professor, Georgia State University, Atlanta, GA. Dr. Petty discloses that he is retained as a consultant by Astra Zeneca Pharmaceuticals and Janssen Pharmaceuticals and serves on the speaker's bureau for Astra Zeneca Pharmaceuticals, Janssen Pharmaceuticals, Abbott Pharmaceuticals, and Avanir Pharmaceuticals.
Attention-deficit/hyperactivity disorder (ADHD) is a common disorder of childhood, and most studies have shown that it is rarely something that a child grows out of. Most young people who have it will continue to have some symptoms—and some of the complications—of ADHD throughout life. This is sometimes missed for two reasons. First, the clinical features of ADHD are usually entirely different in girls and boys; and second, the symptoms and complications metamorphose and migrate as boys and girls become older.
There is a great debate in psychiatry and many allied professions concerning the nature of illness. The issue can be summarized very quickly: Are we medicalizing normal human variations? Fifty years ago unruly inattentive children were given detention or some other punishment. But now they receive a medical diagnosis and treatment with medication.
This is an important discussion that extends into some of the farthest reaches of human behavior: The argument goes that a person is not allowed to be shy, but is instead socially phobic and in need of a medicine. Another person is not bad, but has a personality disorder and needs hospital treatment rather than incarceration. We all have our own biases in answering those questions. However, in the case of ADHD we can apply a number of commonsense principles to show that it is a real clinical entity. First is good evidence from different types of brain imaging; there are predictable differences in the brains of most people with ADHD. Second is that if left untreated ADHD can cause suffering either to the individual or to other people, and suffering is an important criterion for calling something an illness. Third, untreated or inadequately treated ADHD gives rise to a number of complications.1,2 (See Table 1.)
Thus, the recognition and treatment of ADHD is not a device to make children and adults more tractable, or to help people get better grades in school or have better job evaluations. If untreated, ADHD can have many devastating consequences. Unfortunately, few treatment studies—including medication studies—have examined these consequences, and clinicians need to be aware of these complications when recommending a course of action.
This is particularly important when faced with a question about nonpharmacological approaches instead of using medications. Research has shown that at least 50% of American families who receive treatment for ADHD in specialty clinics also use complementary or alternative medical therapies excluding diet.3 Yet only 12% report this use to their clinicians. This article was prompted by a recent national survey that indicated that 92% of pediatricians had been asked by parents about complementary therapies for ADHD.
ADHD is common: 5-8% of all U.S. school-age children are estimated to have the disorder and in 36.3% of cases it persists into adulthood,1 though some of the clinical manifestations may change over time. There is marked geographical variation in diagnosis, with the highest rates of diagnosis being in the northeastern United States.4 Nearly 4.5% of American adults fulfill criteria for ADHD,5 though some studies have found high rates of partial forms of ADHD (i.e., many adults learn to compensate for their difficulties).
First described more than 150 years ago, both the incidence and prevalence appear to be increasing. This increase does not appear to be a reflection of increasing awareness or changing diagnostic criteria, and there are a number of theories that attempt to explain it:
Table 2 details the current DSM-IV-TR criteria for ADHD. The most important point is that the problem has to have been present before the age of 7, and has to be persistent. An additional problem in diagnosis is that ADHD is highly comorbid: Worry and anxiety disorders, conduct disorder, learning disabilities, oppositional defiant disorder, depression, bipolar disorder, and tics and Tourette's are all more common.
Dietary Manipulations in ADHD
Dietary interventions are the most common type of complementary approach to the treatment of ADHD.
The three main dietary therapies for ADHD are: the Feingold diet, sugar restriction, and avoiding allergens and toxins in food. There are others, but these are the most widely used and also the ones that have been most widely studied. These diets are sometimes used in
The Feingold Diet
The Feingold diet is both the best known and most studied dietary intervention for ADHD. It aims to eliminate three groups of synthetic food additives and one class of synthetic sweeteners:
During the initial weeks of the Feingold program, foods containing salicylates, which include almonds, apples, apricots, blackberries, cherries, cucumbers, grapes, gooseberries, oranges, strawberries, and tomatoes, are removed and are later reintroduced one at a time so that the child can be tested for tolerance. In this phase of the diet, foods like pears, cashews, and bananas are used instead of salicylate-containing fruits.
There has been a great deal of debate about the efficacy of the Feingold and related diets. In a double-blind crossover study, 40 of 55 children with ADHD had significant improvements in behavior after a six-week trial of the Feingold diet.6 An interesting feature was that over 3-6 months, 26 of the children (47.3%) maintained their improvement following liberalization of the diet. In another study, 19 of 26 children responded favorably to an elimination diet.7 It is particularly interesting that when the children were gradually put back on to a regular diet, all 19 reacted to many foods, dyes, and/or preservatives.
A recent meta-analysis identified 15 studies that met predefined criteria of being double-blind and placebo-controlled.8 The authors focused on artificial food colorings, and looked at whether ADHD symptoms worsened in children with ADHD when challenged with a food coloring. There was a common finding: Parents' rating of worsening of symptoms was much higher than that of teachers and health professionals. Parents reported a significant improvement off the food colorings; the teacher and health workers did not. Parental expectation may have been a factor, or the parents and professionals were assessing different aspects of the children's behavior.
There does appear to be an effect of food colorings, but it is small and unstable. There may well be a subset of children who are allergic to food additives and there is increasing evidence that some allergies are more common in children with ADHD.9 There is no credible published research on the use of the Feingold diet or of food additives and/or allergy in adults with ADHD. This author and another analysis of the literature both came to the same conclusion: More research is needed.10
There is an impression that clinicians may be more interested in elimination diets in Europe than they are in the United States. In 2004, a large (n = 1,873) randomized, blinded, crossover trial of 3-year-old children was published.11 Of the original 1,873 children, 1,246 had skin prick tests to identify atopy. After baseline assessment, children were given a diet eliminating artificial colorings and benzoate preservatives for one week. During the next three weeks, the children participated in a within-subject double-blind crossover study, during which they received, in random order, periods of dietary challenge with a drink containing artificial colorings (20 mg daily) and sodium benzoate (45 mg daily)—the active period—or a placebo mixture, as a supplement to their diets. The results showed consistent, significant improvements in the children's hyperactive behavior when they were on a diet free of benzoate preservatives and artificial colorings. They had worsening behavior during the weeks when these items were reintroduced. But once again the improvement was only detected by parents and not by a simple clinic assessment. On the basis of this and other studies, in 2004 schools in Wales mandated the withdrawal of foods containing additives from school lunches. There are not yet any published data on the long-term effects of this change.
The biggest problem with the Feingold and other elimination diets is that they are expensive and hard to follow. Whatever the final results of the controlled studies, those barriers will always limit their utility. It is also essential to ensure that children on any kind of diet maintain adequate nutrition.
Most clinicians will be familiar with the notion that sugar can make children hyperactive. Happily it is not true. At least 10 double-blind studies have failed to show a link between sugar and hyperactivity.10,12,13
The evidence that allergies may be more common in children with ADHD lead to the question whether children with ADHD could be allergic not only to additives, but also to certain foods themselves. When speaking to patients and their families, it is useful to differentiate allergies—the result of abnormal reactivity of the immune system to proteins in food—from sensitivities that are the direct result of substances in food. The notion was strengthened by the observation that celiac disease may be linked to an increased risk of ADHD and other symptoms.14
In an open study of 78 children with ADHD, 90% of whom had previously noticed a reaction to certain foods and who were referred to a diet clinic in London, 59 improved during a "few foods" elimination diet trial that eliminated foods to which children are commonly sensitive.15 There was a huge range of offending foods and additives, but the most commonly observed were cow's milk, wheat, corn, chocolate, and eggs. Nineteen of the children were able to participate in a second phase. This was a double-blind crossover trial of suspected foods or additives that could be disguised by mixing them with food the children could tolerate. The provoking foods produced a significant worsening of behavior and psychological test performance. On this occasion, both raters and parents picked up the effect, and one conclusion of the study was that clinicians should give weight to the observations of parents and teachers.
At one time it was popular to try and identify allergies using the radioallergosorbent test (RAST). Although technically easy to perform, the RAST is now little used because of problems with sensitivity and specificity. In an allergy testing study of 43 food extracts, 52% of children with ADHD (n = 90) had an allergy to one or more of the foods tested.16 Over the next few years several researchers carried out open-label studies in which children with ADHD and food allergies were treated with sodium cromoglycate. However, although some authors claimed benefit, the studies were extremely small, not well designed, and have never been replicated.
Clinicians may well be asked about practitioners and commercial entities that claim to be able to identify food sensitivities with methods ranging from blood and muscle testing to electrical and energetic techniques. Some may be helpful, but a detailed search of the literature has not found any to be of proven efficacy.
Many clinicians recommend that parents keep a diet diary for 1-2 weeks to see if any obvious associations between diet and behavior emerge. They will then try an additive-free diet, low in sugar and avoiding foods that are suspected of exacerbating symptoms.
Good nutrition is a fundamental component of any form of treatment or health maintenance program. But the converse: that food—or constituents or adulterants of food—can cause disease is not so clear. Despite the beliefs of many patients, their families, and the media, the evidence remains far from clear. However, there is enough evidence to warrant further research and to recommend a diet diary and a nutritionally sound elimination diet in selected individuals.
It is also essential for the clinician to emphasize that dietary management is but one aspect of treatment: We must also deal with the psychological effects of ADHD, and its impact on relationships, study, and work habits.
[Editor's Note: Dr. Petty is the author of Healing, Meaning and Purpose and has lectured to more than a quarter of a million people in 45 countries. His newsletter, reports, blogs, and podcasts on health, personal growth, and integration are available at www.richardgpettymd.com or call (770) 554-8812.]
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