The Alkaline diet (also known as the alkaline acid diet and the acid alkaline diet) is a controversial dietary protocol based on the consumption of mainly fresh low sugar fruit, vegetables, roots and tubers, nuts, and legumes and avoiding grains, dairy, meat and excess salt, in order to balance the acidity and alkalinity (the "pH balance") of one's body. In recent years it has been a popular topic among authors of diet and nutrition. A common belief among many medical practitioners, however, is that the blood alkalinity (pH) is not significantly affected by diet, except for pathological cases (e.g., of ketoacidosis produced by diabetes). Without well designed human research studies showing that these diets actually do what they say they can, many qualified dietitians, nutritionists and other health care professionals have not recommended these diets to their patients.
A similar theory, called the Dr. 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. Others who have promulgated alkaline-acid diets include Edgar Cayce, D. C. Jarvis, Robert Young, Herman Aihara,, Fred Shadian and Victor A. Marcial-Vega.