Visit 2: One to 10 days later subjects will be again admitted as an outpatient after a 2-3h fast. They will consume a meal of a bread muffin labelled with 4mg of iron-57 as ferrous fumarate, and a glass of apple juice containing 0 or 25mg ascorbic acid. The order of ascorbic acid supplementation or non-supplementation will be decided by random. No food will be allowed after the meal. After 2h subjects will be discharged home and food allowed.