The Alkaline diet (also known as the alkaline ash diet, alkaline acid diet and the acid alkaline diet) is a dietary protocol based on the consumption of foods which burn to leave an alkaline residue. Minerals containing elements like calcium, iron, magnesium, zinc, copper, are the principal components of the ash, as they are incombustible. This burning is compared to the way in which foods are catabolised to produce wastes. Foods are thus classified[citation needed] as alkaline, acid or neutral according to the pH of the solution created with their ash in water. One of the most famous proponents of the alkaline diet is Robert Young.
In general, the diet involves eating certain fresh citrus and other low-sugar fruits, vegetables, tubers, nuts, and legumes and avoiding grains, dairy, meat, sugar, alcohol, caffeine and fungi. Such a diet helps to maintain the balance of the slight alkalinity (7.35-7.45) of blood without stressing the body's regulators of acid-base homeostasis.
Metabolic acidosis may indicate the presence of disease such as diabetic ketoacidosis or may have other causes, like exercise-induced lactic acidosis; likewise metabolic alkalosis may be caused by chronic conditions such as hypokalemia-induced alkalosis, or temporary, such as hyperventilation.
In the absence of these, bodily pH will be maintained within a narrow range irrespective of diet. Rather, the health effects of an alkaline diet are generated by reducing the body's need to utilize internal stores of mineral buffers, such as the calcium stored in bones, to maintain the pH balance, particularly as renal function declines with age.
The wide ranging health claims for this diet originate in the observation that an underlying metabolic acidity is a common denominator among many degenerative and autoimmune diseases.
Studies have been conducted showing certain health benefits (increased bone mass) in specific populations (older people) as a result of taking alkaline (potassium bicarbonate) supplements, with conclusions extrapolated as to the analogous effect of alkaline-rich diet: "Increasing alkaline content of the diet with bicarbonate supplementation significantly reduced levels of the bone turnover markers urinary N-telopeptide and calcium excretion (both P=0.001); Because fruits and vegetables are metabolized to bicarbonate, a dietary approach may have a similar effect."
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. Others who have promulgated alkaline-acid diets include Edgar Cayce, D. C. Jarvis, Robert Young, Herman Aihara, Fred Shadian, and Victor A. Marcial-Vega.
The theory behind the alkaline diet is not widely accepted by the medical community, as is inconsistent with scientific theories of disease.