The effects of diet and stool composition on the net external acid balance of normal subjects.

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Abstract
Whether total effective fixed acid production could be measured in subjects eating whole food diets was determined. We carried out sixteen metabolic balance studies using 3 types of diets during periods when blood pH and serum bicarbonate were normal and stable. Urinary inorganic sulfate and organic acid salts were measured as indexes of acid production. In addition, organic anlons in excess of organic cations, or the converse, in both the diet and the feces was estimated as the difference between the sum of inorganic cation (Na+ + K+ + Ca++ + Mg++) and the sum of inorganic anion (Cl-+ 1.8 P (mmoles)]. Excess organic anions or cations in the diet were assumed to represent potential alkali or acid, respectively. The excess organic anions present in all stools were assumed to represent loss of potential alkali. Total effective acid production was calculated as the sum of urinary inorganic sulfate and organic acid salts minus diet organic anions less fecal organic anions. Good agreement was found when acid production calculated in this way was compared with the quantity of acid simultaneously excreted by the kidney, measured as urinary tltratable acid plus ammonium minus bicarbonate.