The Alkaline Ash Diet is based on the theory that foods, after they are metabolized, leave either an acidic or an alkaline residue (“ash”) in the body. This residue can theoretically lead to the body having either more acidity or more alkalinity with the goal being to have the body be more alkaline than acidic. The theory states that an acidic body, as measured by the acidity or alkalinity (i.e., the pH) of the urine, will lead to an increased incidence of a whole host of maladies from osteoporosis to cancer.

While certain foods certainly leave an acid or alkaline residue depending on what you eat, the body’s acid base balance will not change based on the foods one eats. The acid base balance of the body is very tightly regulated by the kidneys and the scientific literature is very clear that the relative acidity or alkalinity of the foods one eats will not alter the pH of the blood. Moreover, as it relates to people with acid reflux disease, the alkaline ash theory is not applicable because it does not take into account the consequences of food itself causing damage to the throat, vocal folds (larynx), esophagus, lungs, sinuses and teeth. This occurs because of the possibility of PEPSIN being present in these structures.

Pepsin is an enzyme typically found in the stomach that acts to breakdown food when it is in the acidic environment of the stomach. Pepsin gets activated at acidic pH’s, generally most active at pH below 4. So when one consumes highly acidic substances (citrus (grapefruit, orange, pineapple, lemon, lime), vinegar (including apple cider vinegar), tomato, sugary soda), these pepsin receptors get activated which actually damages the throat and esophagus in those with acid reflux disease. Effectively what happens when one consumes highly acidic substances is that what you eat can start eating you.

Fenton TR, Lyon AW, Eliasziw M, Tough SC, Hanley DA (2009). Meta-Analysis of the Effect of the Acid-Ash Hypothesis of Osteoporosis on Calcium Balance. Journal Of Bone and Mineral Research. 24: 1835–1840.

Koeppen BM (2009). The kidney and acid-base regulation. Advances in Physiology Education. 33: 275-281.

Hietavala EM, Puurtinen, R, Kainulainen H, Antti A Mero AA (2012). Low-protein vegetarian diet does not have a short-term effect on blood acid–base status but raises oxygen consumption during submaximal cycling. Journal of the International Society of Sports Nutrition. 9:50-58.

Samuels TL, Pearson ACS, Wells CW, Stoner GD, Johnston, N. (2013). Curcumin and Anthocyanin Inhibit Pepsin-Mediated Cell Damage and Carcinogenic Changes in Airway Epithelial Cells. Annals of Otology, Rhinology & Laryngology. 122:632-641.