Alkaline Phosphatase Activity in Human Milk during the First Month of Lactation

Human milk is the main source of nutrients for a child during the first months of life. Alkaline phosphatase (EC 3.1.3.1) is a very important enzyme in clinical chemistry because of its activity in various tissues and biological fluids, being an indicator of physiological or diseased states. Milk contains several phosphatases, the principal ones being alkaline and acid phosphomonoesterases which have no known function or significance in milk, and have been studied extensively so far. The objective of the present study was to determine the alkaline phosphatase activity and concentration of inorganic phosphorus (P) in colostrum and maturemilk obtained from nursing mothers. Our longitudinal biochemical analysis showed that alkaline phosphatase activities decreased from the 1 and the 2 day of lactation (colostrum) to the nd of the first month of lactation (at day 30). The amount of inorganic phosphates from colostrum increased to the end of the first month (at day 30) of lactation. The alteration between colostral and mature milk alkaline phosphatase activity may be a consequence of theALPtransfer from the blood of mother into the colostrum and milk during breastfeeding. The concentration of nutrients in colostrum and mature milk suffers alterations, including a decrease in alkaline phosphatase activity and anincrease in P, probably in order to satisfy the requirementsof the nursing infant.