Early in my clinical research on the role of diet in ADHD I was surprised at the frequency that mothers reported anaemia. My clinical research collected diet information on over 1000 families. [ See my Masters thesis on diet and behavior and development of the diet ] Often they were very motivated mothers who had attended well to diet hoping that improving nutrition would decrease learning problems in their ADHD children. And they had made an effort to eat more meat to help with their ongoing anaemia, so the problem was not related to low intake of iron-containing foods. What was even more surprising was that once they had been on the low-chemical diet for a few months they reported that iron levels were much closer to normal. In clinical research we listen to everything our patients tell us and gradually note important ideas that are mentioned often. After the early reports I asked about anaemia more and heard the same story more often. Then I learned that salicylate interferes with iron absorption and realized that the problem and the improvement on a low salicylate diet made sense. We do not know whether salicylate only has this significant effect in food sensitive people.
I suspect food sensitivity is in the genes, but can manifest itself in older age, (IBS, where symptoms happen after 50, fits this idea), as well as in infancy and early life. Sometimes it can happen when someone leaves home where the foods suited the family and they had few symptoms, but when the diet broadens symptoms happen. patients often say “Why is this happening to me now?” and the answer is that we do not know. But we can help with the symptoms.