Most infants consume fruit juices by 6 months of age. However, fruit juices containing sorbitol may be associated with carbohydrate malabsorption without clinical symptoms. We hypothesized that increased physical activity and metabolic rate may be associated with carbohydrate malabsorption.
Physical activity and metabolic rate were determined in 14 healthy infants ([mean±SD] age, 5.1±0.8 months; weight, 7.8±1.1 kg; length, 67±4.2 cm; and body fat, 26%±5%) for 3 hours in a respiratory chamber. Seven were fed pear juice, and the other 7 were fed white grape juice (120 mL) after a 2-hour fast. Pear juice contains sorbitol and a high fructose–glucose ratio, whereas white grape juice is sorbitol free and has a low fructose–glucose ratio. Carbohydrate absorption was determined by breath hydrogen gas analysis. The study was double-blinded.
When compared with the infants without carbohydrate malabsorption (peak breath hydrogen level <20 ppm above baseline), 5 of the 7 infants fed pear juice and 2 of the 7 infants fed white grape juice exhibited carbohydrate malabsorption (peak breath hydrogen level ≥20 ppm above baseline; P<.01). These infants also exhibited both increased physical activity (P<.001) and metabolic rate (P<.05) after juice consumption in comparison with infants with normal carbohydrate absorption. When grouped according to the type of juice consumed, only infants fed pear juice exhibited increases in physical activity (P<.01).
Carbohydrate malabsorption is associated with increased physical activity and metabolic rate in infants. Most of the infants who had carbohydrate malabsorption consumed pear juice. Therefore, fruit juices containing sorbitol and high levels of fructose may not be optimal for young infants.