Choline supplementation reduces urinary carnitine excretion in humans.

Two experiments were conducted to determine the effects of supplementary choline and/or pantothenate on the carnitine and lipid status of free-living humans. Analyses of carnitine and cholesterol fractions, triacylglycerols, and creatinine were determined in serum and/or urine. In experiment 1, adults receiving 13.5 mmol choline plus 1.4 mmol pantothenate/d had a significant decline in urinary carnitine excretion and renal clearance with nonesterfied carnitine (NEC) declining the most dramatically, 84%. Additionally, serum NEC and total carnitine concentrations decreased significantly. No changes were observed in any of the serum lipids examined. In experiment 2, subjects took 0.20 mmol and 0.02 mmol/kg choline or pantothenate, respectively. Choline, but not pantothenate, supplementation significantly decreased urinary carnitine excretion, renal clearance, and fractional clearance of NEC. We conclude that supplementary choline maintained serum carnitine concentrations by conserving urinary carnitine. Moreover, these observations merit additional investigation to determine metabolic and functional consequences of choline and carnitine interactions in humans.