Abstract
Despite the important role that insulin plays in the human body, very little is known about its presence in human milk. Levels rapidly decrease during the first few days of lactation and then, unlike other serum proteins of similar size, achieve comparable levels to those in serum. Despite this, current guides for medical treatment suggest that insulin does not pass into milk, raising the question of where the insulin in milk originates. Five mothers without diabetes, 4 mothers with type 1, and 5 mothers with type 2 diabetes collected milk samples over a 24-hour period. Samples were analysed for total and endogenous insulin content and for c-peptide content. All of the insulin present in the milk of type 1 mothers was artificial, and c-peptide levels were 100x lower than in serum. This demonstrates that insulin is transported into human milk at comparable concentration to serum, suggesting an active transport mechanism. The role of insulin in milk is yet to be determined; however, there are a number of potential implications for the infant of the presence of artificial insulins in milk.
Highlights
Insulin, a key hormone in blood glucose homeostasis, has been detected in human colostrum at supraphysiological levels (114–306 mU/L) before decreasing to similar concentrations to those found in blood in the fasting state by day 5 postpartum in healthy mothers [1, 2]
The purpose of this study was to identify the origin of the insulin present in the milk of mothers with type 1 diabetes mellitus as either endogenous or exogenous by determining the levels of total insulin, endogenous insulin, and c-peptide in the milk compared to mothers without diabetes mellitus
Fore and hind milk insulin levels were averaged for the purpose of investigating any circadian variation; and this analysis showed no significant variation in insulin levels during different time points during the day
Summary
A key hormone in blood glucose homeostasis, has been detected in human colostrum at supraphysiological levels (114–306 mU/L) before decreasing to similar concentrations to those found in blood in the fasting state by day 5 postpartum in healthy mothers [1, 2]. Recent work by Tiittanen et al [3] has demonstrated that insulin is present in the milk of mothers with type 1 diabetes mellitus, who lack any endogenous insulin secretion from the pancreas. They demonstrated that levels of insulin are significantly higher (P < 0.001) in milk from type 1 diabetic mothers than that of nondiabetic control mothers, at both days 3 to 7 postpartum and 3 months postpartum. Current medical guides state that insulin is a peptide that is too large to be secreted into milk [5,6,7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
