In 1924, Haas achieved notice when he published a medical paper detailing his use of a banana diet for the treatment of children diagnosed with celiac disease. Haas concluded that bananas enabled the breaking up of starches and the conversion of cane sugar into fruit sugar, which prevented the debilitating diarrhea of celiac disease. Haas’ research led to the development of the Specific Carbohydrate Diet, a nutritional regimen that restricted the use of complex carbohydrates (disaccharides and polysaccharides) and eliminated refined sugar, gluten and starch from the diet.
During his career, Haas treated over 600 cases of celiac disease. In 1951, he joined his son, Dr. Merrill P. Haas, in publishing the medical textbook The Management of Celiac Disease.