Vitamin E Pharmacokinetics and Biomarkers in Normal and Obese Women
Status:
Recruiting
Trial end date:
2025-12-31
Target enrollment:
Participant gender:
Summary
Background:
- Vitamin E is an antioxidant that reduces the damaging effects of oxygen in the body.
Most American men (90%) and women (96%) do not get enough vitamin E from their diets;
however, the amount of vitamin E needed by the body has been studied only in men, not
women. In addition, it is unknown whether another antioxidant, vitamin C, helps vitamin
E in protecting the body. Because vitamin E is a fat-soluble vitamin, how much body fat
a person has could affect the amount of vitamin E needed for protection.
Objectives: This study has three arms to examine vitamin E requirements:
- To determine the amount of fat required to get the best vitamin E absorption from a
meal.
- To determine the amount (i.e., best dose) of vitamin E that must be consumed before it
can be measured in the blood.
- To examine how vitamin E and vitamin C work together in the body, in conjunction with
diet and vitamin supplements.
Eligibility:
- Arms 1 and 2: Women between the ages of 18 and 40 years who have a normal weight and
body mass index (BMI) of 27 or less.
- Arm 3: Women between the ages of 18 and 40 years who have a normal weight (BMI 27), who
are overweight (BMI > 27), or who are overweight (BMI > 27) and have non
insulin-dependent diabetes.
Design:
- Arm 1: Five studies, each lasting 1 month with 1 month off between studies (total study
= 10 months). Participants will take 500 1,000 mg of vitamin C twice daily for 2 weeks
before admission to the clinical center for 1 week.
- Study 1: Participants will eat breakfast containing a known amount of fat, after which
they will take a vitamin E pill as well as receive an IV injection of vitamin E. Other
foods contain only negligible amounts of vitamin E. Blood and urine samples will measure
levels of vitamin E and other substances.
- Studies 2 5: Outpatient visits will consist of the same tests as in Study 1; however,
the amount of fat in the breakfast will range from 0% to 40% in random order. During one
of the studies, an adipose tissue biopsy will be collected to determine how much vitamin
E is in the tissues.
- Arm 2: Five studies, each lasting 1 month with 1 month off between studies (total study
= 10 months). Preparation for Arm 2 is the same as in Arm 1. The proportion of fat,
muscle, and water in the body will also be measured.
- Study 1: Participants will eat breakfast containing 30% fat, after which they will take
a vitamin E pill as well as receive an IV injection of vitamin E. Conditions and
procedures are the same as in Arm 1.
- Studies 2 5: Outpatient visits will consist of the same tests as in Study 1; however,
the amount of vitamin E in the breakfast will range from 2 to 30 mg in random order.
- Arm 3: Outpatient (2 to 6 weeks) and inpatient studies (4 to 6 weeks).
- Outpatient study: Participants will take 500 1,000 mg of vitamin C daily and provide
blood and urine samples, as well as an adipose tissue sample.
- Inpatient studies: Two vitamin E inpatient studies. Before these begin, participants
vitamin C blood levels will be reduced by means of a diet low in vitamin C. Blood tests
will determine how quickly vitamin C leaves the body. Once the vitamin C level is
reduced, the first vitamin E study will begin.
Study A: The procedure for this study is the same as in Arm 2, Study 1.
Study B: The procedure for this study is the same as in Study A, except that the participants
blood vitamin C levels will be higher.
Phase:
Phase 1
Details
Lead Sponsor:
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)