Plasma Micronutrient Concentrations in Infants Undergoing Therapy for Phenylketonuria

Abstract

Many reports have suggested problems with trace and ultratrace mineral status in patients treated for PKU. We describe iron and trace- and ultratrace mineral status of 27 infants with PKU. Each infant was fed Phenex TM-1 Amino Acid Modified Medical Food with Iron as their primary protein source during six months following diagnosis. Mean (± SEM) daily intakes of copper (Cu) (1.1±0.1 mg), iron (11.6±0.7 mg), manganese (Mn) (0.5±0.1 mg), selenium (Se) (22.6±0.8 mcg) and zinc (8±0 mg) met or exceeded the 1980 Recommended Dietary Allowances (RDA) and Estimated Safe and Adequate Daily Dietary Intakes (ESADDI). However, 12 infants failed to consume 100% of 1980 RDA for iron and 28 subjects failed to consume 100% of 1980 ESADDI for Mn. Despite these suboptimal iron intakes, mean (± SEM) plasma ferritin concentration was 42.1±5.5 ng/mL at 6 months of study; one infant had subnormal plasma ferritin concentrations (i.e.<12 ng/mL). Mean (± SEM) plasma Mn concentration was 1.1±0.2 mcg/L; four infants had low concentrations (i.e.<0.5 mcg/L). Mean (± SEM) plasma concentrations of Cu, molybdenum (Mo), Se and zinc were normal for age. Mean plasma Mo concentration was normal even though no dietary Mo was added to Phenex-1 medical food, suggesting that amounts naturally occurring are adequate for needs. Phenex-1, in the amounts fed, supported normal trace and ultratrace mineral status. Our data suggest that when elemental diets are fed, Cu, iron, Se and zinc intakes should be greater than either the 1980 or 1989 RDA and ESADDI, but that the 1989 RDA for Mn (0.3 mg/day) may be adequate for infants during the first 6 months of life.