Visit 3: Two weeks (+/- 3 days) later they will be readmitted after a 2-3h fast and the second visit repeated. During this admission the apple juice will contain either 0 or 25mg ascorbic acid, the opposite of what was given to the subject in visit 2. Immediately prior to administration of the second test meal, 10mL blood will be drawn for measurement of iron nutritional parameters (e.g. CBC, serum ferritin) and iron isotope ratio measurement. Incorporation of iron-57 will be used to calculate iron absorption from the test meal given during visit 2, and incorporation of iron-58 used to measure absorption from the reference dose (a measure of iron status). No food will be allowed after the meal and blood draw. After 2h subjects will be discharged home and food allowed.