GAPS, which is short for the "Gut and Psychology Syndrome," is a non-medical diagnosis said to be responsible for a mind-boggling array of disorders, ranging from irritable bowel syndrome, the much more serious inflammatory bowel disease and most other digestive disorders (including constipation and diarrhea) to urinary tract infections, anemia, food allergies, asthma and even acne. The main premise is that toxins in the digestive tract escape because of increased intestinal permeability ("leaky gut"), a condition not recognized by most conventional physicians. Leaky gut is said to stem from damage to the intestinal lining that allows some bacteria and their toxins, incompletely digested proteins and fats, and waste products of digestion to enter the bloodstream. In the GAPS scenario, these escapees find their way to the brain where they can cause depression, learning disabilities, ADHD, even autism. The trouble is, Gut and Psychology Syndrome has not been described scientifically and its existence is unproved.
I discussed your question with Gerard Mullin, M.D., associate professor of medicine and an integrative gastroenterologist at Johns Hopkins Hospital, who tells me that the GAPS diet lacks a clear scientific rationale and is challenging to follow even for those who believe that it may be worthwhile. He notes, however, that there is a parallel line of thinking that individuals with autism, learning disabilities and depression often do have food sensitivities, an altered gut microbiome (a term for all the microorganisms in the gut), and perturbations in their gut function. Dr. Mullin adds that gut dysfunction may accompany autism, but says he has seen no evidence that autism can be reversed by following gut rescue protocols.
Dr. Mullin explains that the GAPS diet is an offshoot of the earlier Specific Carbohydrate Diet (SCD), developed in the 1920's to treat patients with celiac disease and still promoted as an alternative treatment for a number of digestive disorders. The SCD diet eliminates all grains, dairy products, processed sugars and canned vegetables. I've seen no studies indicating the SCD diet to be effective for any of the disorders for which it is promoted.
The GAPS diet eliminates dairy products and all sugars, is low in fruits and grains and includes broth made from fish and meat bones to help restore gut barrier function, as well as probiotic foods to restore a healthy mix of gut flora. Dr. Mullin tells me that he has patients who have tried this diet but so far, the results have not impressed him.
Andrew Weil, M.D.