New Study Ties Processed Foods To ADHD in 78% of Children
According to a new study, just published in Lancet Journal, a diet free of processed foods significantly reduces the symptoms of ADHD in 78% of 4-8 year old children. This 5-week study involving 100 subjects found that 63% of them experienced a relapse in ADHD symptoms upon re-introduction of problem foods into the diet.
This randomized crossover study was titled the Impact of Nutrition on Children with ADHD (INCA). Patients in the Netherlands and Belgium were enrolled via announcements in medical health centres and through media announcements. In the open-label phase (or first phase), children aged 4—8 years, who were diagnosed with ADHD, were randomly assigned to either 5 weeks of a restricted elimination diet (diet group) or to instructions for a healthy diet (control group). 
In the second phase, those children who responded positively (with an improvement of at least 40% on the ADHD rating scale) proceeded into the second phase, with a 4-week double-blind crossover food challenge, in which they were exposed to either a high-IgG or low-IgG food diet (classified on the basis of every child’s individual IgG blood test results).
Traditionally, food allergies have been defined as allergic reactions to specific foods which produce a Type I allergic reaction involving IgE (Immunoglobulin E) antibodies. An antibody is a protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. Actual IgE food allergies are somewhat uncommon, with estimates that 4% of the population have food-based allergic disorders. The most common food allergy triggers are the proteins in cow’s milk, eggs, peanuts, wheat, soy, fish, shellfish and tree nuts. IgE allergic reactions to foods can occur within minutes or a few hours after the food is eaten and may lead to many different symptoms including hives, swelling around the mouth, asthma, diarrhea, vomiting, eczema and even life threatening anaphylaxis (which is a severe adverse reaction involving the major body systems).
An alternative theory regarding food allergies is that another, more subtle form of food allergy exists. This type of food allergy (sometimes also referred to as a food sensitivity), is said to involve IgG (Immunoglobulin G) antibodies, and is believed to be measurable by an IgG ELISA/EIA Food Allergy Test. This IgG allergy theory tends to be supported more by naturopathic medicine than by traditional allergists and immunologists.
According to the IgG food allergy theory, IgG antibodies are associated with non-atopic or “delayed” food reactions that can worsen or contribute to many different health problems. These reactions are more difficult to notice since they can occur hours or even days after consumption of an offending food. Often the offenders are frequently eaten foods that are hard to avoid, such as milk, corn, and wheat. These “hidden” food allergies are said to affect as many as 60% of the population, and are believed to contribute to a variety of disorders, including ADD/ADHD, migraines, Rheumatoid Arthritis etc. 
This is one of the most interesting aspects of the study, because these researchers actually tracked the children’s IgG levels, from before the study began, then again following the first phase, and once more after the IgG-based food challenges (the 2nd phase).
In the second, or challenge phase, following introduction of either high-IgG or low-IgG foods, relapse of ADHD symptoms were observed in 19 of 30 (63%) children, independent of the IgG blood levels.
The authors concluded that strictly supervised restricted elimination diets are a valuable instrument to assess whether ADHD is induced by food, however prescribing diets on the basis of IgG blood tests should be discouraged.
These findings agree well with previous studies that revealed that poor diet is strongly associated with ADHD, particularly when children are exposed to foods high in preservatives and food colorings, better known as processed food or junk food .
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- Effects of a Restricted Elimination Diet on the Behaviour of Children With Attention-deficit Hyperactivity Disorder (INCA study): A Randomised Controlled Trial
The Lancet 2011 (Feb 4); 377 (9764): 494–503
- IgG food allergies – are they real?