2. A four-week feeding trial will be implemented to assess the change in plasma zinc concentration among young adult men who receive: a) bread fortified with a moderate amount of zinc and a liquid vitamin preparation between meals; b) bread fortified with a large amount zinc and a liquid vitamin preparation between meals; c) non-zinc-fortified bread and a liquid vitamin preparation between meals [negative control group]; and d) non-zinc-fortified bread and a zinc-containing liquid vitamin preparation between meals [positive control group].