Maximum permissive dosage of lactose and lactitol for transitory diarrhea, and utilizable capacity for lactose in Japanese female adults.

This study aims to estimate the tolerable lactose intake which can be utilized in the digestion by lactase and in the fermentation by intestinal microbes in Japanese female adults. The first, the maximum permissive dosage of lactose not to induce transitory diarrhea was estimated based on the oral ingestion of lactose at several dose levels in all the subjects, and compared with that of lactitol which is not hydrolyzed by digestive enzymes. A second lactose tolerance test involving 10 g and 30 g of lactose was carried out in 10 subjects showing resistance to diarrhea, and serum glucose and insulin levels and the amount of hydrogen excreted in the breath were measured for comparison with those of glucose and lactitol. Subjects were 43 Japanese female adults (average: age 20.5+/-2.1 y, weight 51.3+/-5.1 kg) who had not been diagnosed as having either hypolactasia or being lactose intolerant. Serum glucose and insulin levels were scarcely elevated following the ingestion of both 10 g and 30 g of lactose, while the amount of hydrogen excreted in the breath was greatly increased following the ingestion of 30 g of lactose, but these levels were less following the ingestion of 10 g of lactose. In contrast, the ingestion of 15 g of glucose significantly increased blood glucose and insulin levels, while no hydrogen was detected in the breath. The maximum permissive dosage of lactose not to induce transitory diarrhea was 0.72 g/kg of body weight and that of lactitol was 0.36 g/kg of body weight in Japanese adults. The digestive capacity of lactase is less than 10 g of lactose by single ingestion, while intestinal microflora are able to ferment approximately 20-30 g of lactose. In addition, the ingestion of more than 10 g of lactose might be contributed as prebiotics.