[dkarl]

This statement is necessary because the normal way people approach this problem is to declare one food the culprit, cut out that food, perceive that the problem has been cured, and declare success. There's a placebo affect, for one thing, which would be transmitted from parent to child through the parent's mood and expectations, plus there are random fluctuations in the child's behavior from day to day that will be attributed to whatever is foremost in the parent's mind, which in this case would be the alteration in diet.

People do this stuff all the time when cutting out gluten, starting to take fish oil, etc. It's really weird how someone will choose one thing at random out of all the alternatives, because that thing was pitched to them at just the right time by just the right person, and immediately start to believe it is a powerful force in their lives. There are dozens of dietary "miracle cures" for ailments ranging from depression to acne, and for each one, there are many people who swear by it. A trained doctor can be helpful in tempering expectations, reminding parents that short-term changes can't be taken seriously, and forcing a patient approach.

For instance, if peanut butter is cut from the kid's diet, and two days later the kid has a really bad day at school, many parents would jump to the conclusion that peanut butter was the only thing keeping the kid sane and start feeding it to him every day in every form they could think of. That would be a very bad thing if peanut butter was actually what was causing the problem. The doctor's job is to persuade the parents to be patient and evaluate the evidence more reasonably.