Maximum Permissive Dosage of Lactose and Lactitol for Transitory Diarrhea, and Utilizable Capacity for Lactose in Japanese Female Adults

Abstract

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 sub-jects, and compared with that of lactitol which is not hydrolyzed by digestive enzymes. A second lactose tolerance test involving 10g and 30g of lactose was carried out in 10 sub-jects 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±5.1kg) 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 10g and 30g of lactose, while the amount of hydrogen excreted in the breath was greatly increased following the ingestion of 30g of lactose, but these levels were less following the ingestion of 10g of lactose. In contrast, the ingestion of 15g 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 0.72g/kg of body weight and that of lactitol was 0.36g/kg of body weight in Japanese adults. The digestive capacity of lactase is less than 10g of lactose by single ingestion, while intestinal microfiora are able to ferment approximately 20-30g of lactose. In addition, the ingestion of more than 10g of lactose might be contributed as prebiotics.