Inclusion Criteria:

• We propose to study of five thousand male and female subjects between the ages of 18 and 65. This will include healthy subjects and subjects with type 1 or type 2 diabetes. To be included in the study, study subjects should
• * be in good general health
• * have no significant illnesses that compromise clinical stability other than the complications of diabetes mellitus alone or in the context of metabolic syndrome. Subjects with ischemic heart disease and/or peripheral artery disease are eligible for arm 1 of the protocol.
• * have serum creatinine \< 2.5
• * for healthy volunteers, be normotensive at the time of the study, with a blood pressure less than or equal to 140/90
• * for diabetic subjects, blood pressure less than or equal to 170/95 as long as clinically stable and in usual state of health, for example, no chest pain, shortness of breath, headache, syncope or fatigue
• The aim of this study is to determine whether diabetic subjects lose vitamin C in the urine in their normal clinical condition (i.e. while on treatment) and not in the native untreated state of uncontrolled hyperglycemia. Therefore the patients will not discontinue medication.
• EXCLUSION CRITERIA (for arm 1):
• Exclusion criteria will include the following:
• * significant organ malfunction leading to clinical instability including liver disease, pulmonary disease, stroke and anemia at investigator discretion
• * serious or chronic illness or history of serious or chronic illness resulting in clinical instability other than complications of diabetes
• * pregnancy
• * alcohol abuse, drug addiction or the use of illegal drugs
• * positive HIV or hepatitis (B or C) screening tests (subjects will be notified of these test results).
• * presence of other concomitant conditions which in the judgment of the investigators can influence vitamin C metabolism or vitamin C renal handling
• EXCLUSION CRITERIA (for arms 2 and 3):
• Exclusion criteria will include the following:
• * significant organ malfunction leading to clinical instability including liver disease, pulmonary disease, ischemic heart disease, heart failure, stroke, peripheral vascular disease, and anemia at investigator discretion
• * other serious or chronic illness; history of serious or chronic illness; coronary artery disease, or peripheral vascular disease resulting in clinical instability
• * pregnancy
• * alcohol abuse, drug addiction or the use of illegal drugs
• * positive HIV or hepatitis (B or C) screening tests (subjects will be notified of these test results).
• * presence of other concomitant conditions which in the judgment of the investigators can influence vitamin C metabolism or vitamin C renal handling
• For inpatient subjects, an additional exclusion criterion is consumption during the hospitalization of any foods or beverages other than those in the vitamin C free diet.