Lactose is the primary carbohydrate source in human milk, providing approx. 40% of the energy value to an infant 57Holsinger, V. H. (1996). Handbook of Milk Composition,edited by Robert G. Jensen. Academic Press, San Diego, 1995, 919 pp., $89.95. Journal of Food Composition and Analysis. https://doi.org/10.1006/jfca.1996.0035. According to multiple legislative requirements, lactose is the carbohydrate source of choice for infant milk formula.