By administration of test meals #1 (iron in alginate beads) and #4 (iron in a capsule) the possible protective effect of alginate on iron absorption will be investigated. By administration of test meal #2 (iron in alginate beads + calcium capsule)and #3 (iron in a capsule + calcium in a capsule)the study will investigate whether alginates can bind calcium (a well-known iron inhibitor) in vivo, thus diminish the potential negative effect of calcium on iron absorption.