Hypochloremic alkalosis in infants associated with soy protein formula

Thirteen infants, 2 to 10 months of age, developed hypochloremic alkalosis (serum chloride 59 to 92 mEq/l) while taking Neo-Mull-Soy (Syntex), a soy-based formula low in chloride (measured to be 0 to 2 mEq/l) but with considerable potassium citrate. Range of symptoms included lethargy, anorexia, mild spitting up, diarrhea, hematuria, and growth failure. Urine chloride excretion was less than 3 mEq/l. Plasma renin activity or aldosterone, measured in six infants, was elevated. All responded promptly to supplemental salt. One infant receiving Neo-Mull-Soy redeveloped alkalosis when supplemental salt was discontinued. Two of nine apparently normal infants receiving Neo-Mull-Soy also had hypochloremia (85, 86 mEq/l). Three of four receiving Prosobee (Mead Johnson; Cl content 7 mEq/l) had urine chloride concentration less than 20 mEq/l. The chloride content of some infant formulas is insufficient to offset salt losses following mild stress.