The acid-ash hypothesis is a medical hypothesis which suggests that excessively acidic diets may result in a number of identifiable health effects, including an increased risk of osteoporosis.[1] It has received some attention in the lay community, and has been used to support the diet known as the Alkaline diet.[1] According to the hypothesis, acid ash is produced by meat, poultry, cheese, fish, eggs, and grains. Alkaline ash is produced by fruits and vegetables, except cranberries, prunes and plums. Since the acid or alkaline ash designation is based on the residue left on combustion rather than the acidity of the food, foods such as citrus fruits that are generally considered acidic are actually considered alkaline producing in this diet.[2]