Medical problems which will preclude participation in the study include: pregnancy; chronic or active dermatological disease; chronic anemia (thalassemia, etc.); diabetes mellitus (fasting blood glucose in excess of 140 mg/dl); active or chronic pulmonary disease including COPD, chronic bronchitis, or asthma requiring medications; active or chronic gastrointestinal disease including gastric and duodenal ulcer disease and inflammatory bowel disease; history of cancer except for dermal lesions; intestinal malabsorption, chronic or active renal disease including a serum creatinine above 1.8 mg/dl; chronic or active hepatic disease including hepatitis; HIV infection.