BACKGROUND: Children treated for severe acute malnutrition (SAM) are at risk of refeeding hypophosphatemia. Therapeutic diets have only recently become fortified with phosphorus to meet United Nations (UN) specifications, but to our knowledge no studies have investigated the effect.

OBJECTIVE: The aim was to assess concentrations and correlates of plasma phosphate (P-phosphate) at admission and during treatment and to identify correlates of changes in P-phosphate.

DESIGN: This was a prospective observational study in 6- to 59-mo-old children admitted for treatment of SAM to Mulago Hospital, Uganda. P-phosphate was measured at admission, on the second day of treatment with a therapeutic formula containing 75 kcal/100 mL and 560 mg phosphorus/L (F-75, Nutriset), at the start of the transition to a therapeutic formula containing 100 kcal/100 mL and 579 mg phosphorus/L (F-100; Nutriset), at day 2 of transition, and at discharge.

RESULTS: Among 120 children, mean ± SD P-phosphate at admission was 1.04 ± 0.31 mmol/L and increased by 0.43 (95% CI: 0.35, 0.52) mmol/L during the first 2 d and more slowly toward discharge. Most (79%) children experienced their lowest P-phosphate concentration at admission, and none developed severe hypophosphatemia. P-phosphate was lowest in children with edema and with elevated C-reactive protein, and a lower increase was seen with increasing caretaker-reported severity of illness. Partially or fully replacing F-75 with rice porridge (i.e., a local practice to reduce diarrhea) during the first 2 d of stabilization was associated with a 0.34-mmol/L (95% CI: 0.18, 0.50 mmol/L) lower increase in P-phosphate during the same first 2 d.

CONCLUSIONS: F-75, which complies with UN specifications and provides 73 mg phosphorus·kg(-1)·d(-1) (130 mL·kg(-1)·d(-1)), seems to prevent refeeding hypophosphatemia in children with SAM. Replacing this formula with rice porridge during the first days of treatment to manage diarrhea may have an adverse effect on P-phosphate concentrations. This study was registered at http://www.isrctn.com as ISRCTN55092738.