The Alkaline diet (also known as the alkaline ash diet, alkaline acid diet, acid ash diet, and the acid alkaline diet) is a diet based on the scientifically unsupported theory that certain foods, when consumed, leave an alkaline residue, or ash. Minerals containing elements like calcium, iron, magnesium, zinc, copper, are said to be the principal components of the ash. A food is thus classified as alkaline, acid or neutral according to the pH of the solution created with its ash in water. Proponents suggest adhering to an alkaline diet might prevent cancer, fatigue, obesity, allergies, as well as increase bone health. One of the most famous proponents of the alkaline diet is Robert Young, who has come under scrutiny from the National Council Against Health Fraud. Others who have promulgated alkaline-acid diets include Edgar Cayce, D. C. Jarvis, and Herman Aihara. A similar theory, called the Hay diet, was developed by the American physician William Howard Hay in the 1920s. A later theory, called nutripathy, was developed by another American, Gary A. Martin, in the 1970s.