Lactose: a milk‐specific carbohydrate enabling homeostatic regulation of glucose and insulin (623.12)

Abstract

Lactose, a disaccharide of glucose and galactose, is uniquely present in mammalian milk. Human milk provides the infant with about 40% energy as lactose and 50% from fat. With 6‐7 g/dL lactose, the breast fed infant consumes high carbohydrate/kg body wgt, suggesting carbohydrate induced hepatic lipogenesis would be problematic with a high fat milk diet. However, galactose, unlike glucose is non‐insulinogenic and shows high hepatic clearance. We propose lactose in human milk confers unique metabolic advantage to the infant by delivering non‐insulinogenic carbohydrate which can be slowly metabolized in the liver to glucose or to support fatty acid oxidation. We determined insulin, glucose, triglyceride, free fatty acid and amino acid responses in 16 healthy adult men given in random order 650 mL carbohydrate‐free infant formula reconstituted to contain 50g lactose, glucose, sucrose or corn syrup solids. The milk formula was given 3 hr after a lactose and sucrose‐free meal, then again after 3 hr, to model the carbohydrate load and continuous feeding of breast‐fed infants. Blood was drawn every 15 min, and total and incremental area‐under‐curve change in insulin and glucose determined. Lactose gave a significantly lower rise in plasma insulin and glucose, in the first and particularly second 3 hr following intake, compared to glucose or corn syrup solids (P <0.001). Individual variability in triglyceride responses was high, with no difference due to carbohydrate in this 6 hr study. We show lactose enables maintenance of glucose and insulin equilibrium, avoiding high postprandial peaks achieved with glucose or corn syrups in milk fed at 3 hr intervals. We propose an important metabolic homeostatic role for lactose as carbohydrate source in human milk. Supported by Mead Johnson Nutrition.Grant Funding Source: Mead Johnson Nutrition