PRAL Calculator (Potential Renal Acid Load of a Diet or Food)

How it works

PRAL (mEq) = 0.49 × protein (g) + 0.037 × phosphorus (mg) − 0.021 × potassium (mg) − 0.026 × magnesium (mg) − 0.013 × calcium (mg) · NEAP (Frassetto) = 54.5 × protein (g) ÷ potassium (mEq) − 10.2

Remer and Manz (1995) built PRAL to predict how much acid a diet or food leaves for the kidneys to excrete. Protein (through sulfur amino acids) and phosphorus generate acid, while potassium, magnesium and calcium salts — mostly from fruit and vegetables — generate base; each coefficient accounts for the nutrient’s intestinal absorption and charge. A positive value means acid-forming and a negative value base-forming. Enter a whole day’s intake for your diet’s PRAL, or the nutrients in 100 g of a food to compare foods; meat, cheese and grains score positive, most fruit and vegetables negative.

Worked example

A day with 90 g protein, 1,300 mg phosphorus, 3,000 mg potassium, 350 mg magnesium and 900 mg calcium: PRAL = 44.1 + 48.1 − 63 − 9.1 − 11.7 = 8.4 mEq per day — mildly acid-forming. The Frassetto NEAP estimate is 53.7 mEq per day.

Sources: Remer T, Manz F (1995) Potential renal acid load of foods and its influence on urine pH. J Am Diet Assoc 95:791–797 · Frassetto LA et al. (1998) Estimation of net endogenous noncarbonic acid production in humans from diet potassium and protein contents. Am J Clin Nutr 68:576–583

Frequently asked questions