Lactose can be a concern for many adults as fewer than half of us can process lactose sugar from dairy effectively and we may experience symptoms of gas or other digestive upset. This is because over the age of 5 we start producing less of the enzyme (lactase) needed to process the sugar.
Babies need lactose though!
Lactose makes up to 90% of the carbohydrate and 40% of the calorie content in human milk. Over time, lactose increases in milk, too.
Babies need lactose for:
• Immune system function and maturity
• Brain development from galactose (one of the sugars that makes up lactose
• Vitamin absorption of calcium, zinc, and magnesium
• Supporting the healthy gut bacteria populations
• Maintaining healthy blood sugar levels
Also, lactose supports milk production as it draws water into the milk making cells! In addition, your milk contains the lactase enzyme needed to help baby process the sugar.
The most common reasons for lactose sensitivity are screened for during the early newborn period (galactosemia and congenital lactase deficiency) so it's unlikely that your baby is reacting poorly to the lactose in your milk.
Some infant formulas market on the concern that baby is reacting poorly to lactose by replacing it with corn syrup or maltodextrin, marketing it as a solution for gas and fussiness. If you are feeding some or all formula to your baby, it's rarely necessary to use a low or lactose-free product. Most of the time, if a baby is having symptoms from formula feeding, the protein part of the ingredients is what needs to be changed.
References:
del Carmen Tocaa, M., Fernándezb, A., Orsic, M., Tabaccod, O., & Vinderolae, G. (2022). Lactose intolerance: myths and facts. An update. Arch. Argent. Pediatr, 120, 59-66.
Noble, L., & Rosen-Carole, C. (2022). Breastfeeding Infants With Problems. In Breastfeeding (pp. 457-501). Elsevier.
Cheema, A. S., Stinson, L. F., Rea, A., Lai, C. T., Payne, M. S., Murray, K., ... & Gridneva, Z. (2021). Human milk lactose, insulin, and glucose relative to infant body composition during exclusive breastfeeding. Nutrients, 13(11), 3724.
American Academy of Pediatrics (AAP)
Vandenplas Y. Lactose intolerance. Asia Pac J Clin Nutr. 2015;24 Suppl 1:S9-13. doi: 10.6133/apjcn.2015.24.s1.02. PMID: 26715083.