Alimentary TractAgreement between indirect calorimetry and traditional tests of lactose malabsorption

BackgroundLactose malabsorption occurs frequently and the variable consequent intolerance may seriously impair quality of life. No reliable and convenient test method is in routine clinical practice. A recent animal study showed that the respiratory quotient changed significantly after ingestion of sucrose and lactose in naturally lactase-deficient rats.AimsThis exploratory study evaluated the relevance of monitoring the respiratory quotient after lactose ingestion to detect malabsorption.MethodsHealthy volunteers were identified and classified lactose absorbers and malabsorbers by a lactose tolerance test (25 g). After an overnight fast, a second lactose challenge was performed to monitor hydrogen excretion and respiratory quotient kinetics over 4 h. Participants also completed questionnaires to score and localise their gastrointestinal symptoms.Results20 subjects were enrolled (10 per group, 60% males, mean age 34 ± 4 years). Respiratory quotient kinetics were different between absorbers and malabsorbers during the first 100 min after lactose ingestion (p < 0.01) and during the initial 30-50 min period. Respiratory quotient was significantly, positively correlated to peak glycaemia (R = 0.74) and negatively correlated to hydrogen excretion (R = −0.51) and symptoms score (R = −0.46).ConclusionsIndirect calorimetry could improve the reliability of lactose malabsorption diagnosis. Studies on larger populations are needed to confirm the validity of this test and propose a simplified measurement.