Potential Renal Acid Load (PRAL) Alkalinity
Although it’s popularity has waned in favour of more recent dietary trends, the alkaline diet continues to be touted by many as the key to preventing disease and improving health. According to proponents of the diet, eating acidifying foods, while failing to combine acid-alkaline foods in the right combination, will rob your body of nutrients and lead to a host of diseases ranging from osteoporosis to heart disease and cancer (1).
With any diet, it’s necessary to look beyond the smoke and mirrors to determine if there is sufficient scientific evidence to support its health claims. So, what does the scientific community have to say about the alkaline diet and its supposed benefits?
Chemistry 101 and the PRAL
Before going any further, we need to pause for a brief chemistry lesson on the pH scale in relation to acidity and alkalinity. Food, and other substances, can be classified as “acidic”, “alkaline”, or “neutral” based on their positioning on the following scale:
The Potential Renal Acid Load or “PRAL” of foods was calculated more than 100 years ago as a way to evaluate a food’s acidifying or alkalinizing potential and is represented by the following equation (2):
PRAL = 0.49 x protein (g/day) + 0.037 x phosphorus (mg/d) – 0.021 x potassium (mg/day) – 0.026 magnesium (mg/day) – 0.013 x calcium (mg/day)
A food with a positive PRAL is considered acid-producing, while a negative PRAL is suggestive of a food that is more basic. In general, fruits, vegetables, potatoes, wine, and soda water are considered alkaline, while grains, meats, dairy, fish, and beer are considered acidic (2).
More recently, the PRAL has been criticized for not considering our bodies ability to neutralize acids through normal body systems (3). In addition, the formula classifies phosphate as acidic and sodium as basic, despite evidence showing the contrary (4,5).
