CALCIUM BIOAVAILABILITY FROM BOVINE-MILK AND DAIRY-PRODUCTS IN PREMENOPAUSAL WOMEN USING INTRINSIC AND EXTRINSIC LABELING TECHNIQUES

Stable isotopes were used to compare calcium fractional absorption fro m intrinsically and extrinsically labeled bovine milk as well as intri nsically labeled dairy product and cheese analogue. Healthy Caucasian women were fed a controlled diet for 4 d during the follicular phase o f their menstrual cycle. With breakfast on the third day, participants ingested milk containing Ca-44 (intrinsic) and (CaCl2)-Ca-42 (extrins ic) or dairy products containing Ca-44. Total feces were collected for 2 d prior to and 10 d after isotope ingestion. Polyethylene glycol wa s administered to monitor completeness of fecal collections. Total cal cium was determined by atomic absorption spectrophotometry, and isotop ic abundance was determined by high resolution fast atom bombardment m ass spectrometry. Fractional absorption was determined as the differen ce between the administered isotopic dose and the quantity of Ca-44 or Ca-42 excreted in feces. The fractional absorption of calcium from mi lk was not affected by the method of labeling, lactose content, fermen tation or the chemical form of calcium in dairy products or cheese ana logue.