Factors Affecting the Ability of a High β-Galactosidase Yogurt to Enhance Lactose Absorption

Lactose in yogurt is better absorbed by lactase-deficient subjects than is an equivalent quantity of lactose in milk, presumably because of the microbial activity of the β-galactosidase present in yogurt. In this study, we describe a process that increases the β-galactosidase of yogurt 5- to 6-fold and the ability of this high lactase yogurt to enhance lactose absorption in lactase-deficient subjects. These subjects ingested the yogurt meals after a 12-h fast, and lactose malabsorption was determined by measuring breath hydrogen. Breath hydrogen was reduced 39% following ingestion of high lactase yogurt from that after consumption of conventional yogurt, indicating that the high lactase yogurt enhanced lactose absorption. However, the reduction after high lactase yogurt was less than expected, given the 5- to 6-fold increment in β-galactosidase measured in vitro. In vivo activity of β-galactosidase requires that the enzyme resist acid denaturation in the stomach. The β-galactosidase in high lactase yogurt was much less acid resistant than was the β-galactosidase in conventional yogurt, and the relative inability of high lactase yogurt to enhance lactose absorption was likely due to the destruction of the β-galactosidase in the stomach.