Inter- and intra-individual variations in normal urinary glycine betaine excretion

To establish whether normal human subjects excrete glycine betaine at a constant rate.

Urine was collected from ten normal healthy male subjects for 14 days, during which fluid intake was systematically varied from <800 mL to >3 L per day. Glycine betaine, sorbitol and creatinine excretions were estimated per day and as millimole per mol creatinine.

The intrasubject SD of urine glycine betaine was 3.5 mmol/mol creatinine, and the intersubject SD 5.8 mmol/mol creatinine. The intrasubject SD of plasma glycine betaine was 10.2 mol/L and the intersubject SD 14.2 mol/L. Water load had little effect on glycine betaine excretion and plasma glycine betaine. After 12 years, excretions and plasma concentrations tended to parallel the initial results.

Normal subjects have consistent individual glycine betaine excretions that are not strongly influenced by urine volume. Abnormal excretions, or significant changes in excretion, can be interpreted as indicating a pathological process.