D-lactic acid metabolism after an oral load of DL-lactate.

We have investigated in normal human volunteers the short-term and long-term metabolic consequences of the oral intake of d-lactic acid. After the consumption of 6.4 or 12.8 mmol/kg(0.75) body weight of racemic dl-lactic acid, d-lactate was eliminated from plasma with half-lives of 28.6 +/- 4.3 and 40.4 +/- 5.4 min; its maximum plasma concentrations were 0.34 +/- 0.05 and 0.45 +/- 0.06 mmol/l, respectively. Less than 2% of the administered dose of d-lactic acid was excreted in urine during the 24 hours following intake. There was only a slight, non-significant decrease in blood pH by 0.02 units, accompanied by signs of a mild, compensated metabolic acidosis. A 5 weeks chronic experiment with daily consumption of 6.4 mmol/kg(0.75) body weight dl-lactic acid in 5 volunteers did not result in the accumulation of plasma d-lactate.