 This study will last 31 days. Participants will be admitted to the General Clinical Research Center for 27 days. Participants will be randomly assigned to one of four groups. Participants in Groups 1, 2, and 3 will have 1, 2, or 6 arginine added to their diet in the form of gel capsules. Participants in Group 4 will receive placebo capsules. Participants will be given 24 capsules of different dietary supplements, including the arginine supplements, every day during their hospital stay. 