Vitamin D Supplementation and Immune Function Study for Men and Women
Who is conducting this study?
Charles B. Stephensen, PhD from the USDA, ARS,
What is the purpose of the study?
Vitamin D is required for healthy bones but also for a healthy immune system. The purpose of this study is to determine if the currently recommended level of vitamin D intake, which is based on maintaining bone health, is adequate to maintain a healthy immune system as well, or if a higher intake is required.
Who can participate?
Healthy men and women, ages 20 - 49 years (men) or 20-45 years (women), may be eligible to participate if they have low blood vitamin D levels (25-50 nmol/L). We will check vitamin D levels at the screening visit. Volunteers must be willing and able to come to the research center (WHNRC) on the UC Davis campus or Ticon-1 Building at UCDMC in
Who is NOT eligible to participate?
- are outside of the age ranges described above
- have a BMI of less than 18.5 kg/m2 or greater than 30 kg/m2
- have been diagnosed with anemia, liver or kidney disease, or other health condition that would interfere with vitamin D metabolism or response to immunization (e.g. pancreatic enzyme deficiency, Crohn's disease, cystic fibrosis, celiac disease, surgical removal of part of the stomach or intestines, and some forms of liver disease)
- have been diagnosed with hyperparathyroidism and chronic granulomatous disease, which increase risk of hypercalcemia
- Have planned to travel to a location at which either altitude or latitude would result in significant vitamin D synthesis during the study period.
- Have not previously been vaccinated with TT, or vaccinated within five years
- Have recent, regular use of steroids or antibiotics within the past 4 weeks
- Have current use of nutritional supplements that may alter immune function such as omega 3 fatty acid supplements, anti-inflammatory or anti-convulsion medications
- Have a self-reported history of significant adverse response to previous vaccinations
- Women who are pregnant or lactating
What do I need to do to participate?
You will complete an oral informed consent by telephone. If you are eligible and you decide to participate, a screening visit will be scheduled either at WHNRC (430 West Health Sciences Drive on the UC Davis campus) or at Ticon-1 Building,
If you are eligible, based on the results of the blood tests, you will be asked to begin the study. If you decide to volunteer, you will be randomly assigned to one of the three groups receiving capsules for 12 weeks that contain either 400 International Units (IU), 2,000 IU, or 5,000 IU of vitamin D. Neither you nor the study personnel will know in which group you are placed. You must agree to stop taking all dietary supplements during the study. On study day 1, you will have 85 ml of blood drawn (16 teaspoons) in order to obtain baseline measures of immune function and vitamin D status. You will be asked to avoid eating for 3 hours prior to all study blood draws. You will provide a spot urine sample that will be used to measure urinary calcium. Prolonged high vitamin D intake may cause excessive absorption of dietary calcium. To ensure that you do not have excessive calcium, we will measure urinary calcium levels as a precaution every two weeks. If your urinary calcium levels are higher than expected on a routine urine test, we will ask you to return for a repeat test. If the second test is also high, you will be asked to stop taking vitamin D and discontinued in the study. If you are female, we will also use the urine sample to check for pregnancy. You will be provided with vitamin D capsules in a 1-month supply and will be asked to take one pill per day. You will be provided with a small booklet to keep track of your capsule intake, any illnesses or adverse events, whether you are in direct sunlight for more than 30 minutes on a day, and if you are female, your menstrual cycle. The capsule containers and booklet will be turned in and reviewed with study personnel at each study visit. You will also complete a short food questionnaire. At the end of the first visit, you will be provided a schedule of visits for the next 12 weeks.
At the second visit (week #2) you will provide a spot urine sample. At week #4, 20 mL (4 teaspoons) of blood will be taken to check serum vitamin D and you will provide a spot urine sample. In week #6 a spot urine sample will be taken. In week #8, you will have 85 ml of blood drawn (16 teaspoons), provide a spot urine and receive an injection of tetanus toxoid vaccine. Female volunteers will be tested for pregnancy prior to the vaccination, as pregnant women should not receive this vaccine. In week #9, you will have 85 ml of blood drawn (16 teaspoons). In week #10, you will have 85 mL (16 teaspoons) of blood drawn and provide a spot urine, and in week #12 you will have 85 mL (16 teaspoons) of blood drawn and provide a spot urine. At week #12, you will also turn in all remaining pill containers and booklets. Each study visit will take approximately 1 hour.
What are the benefits to you from this study?
You will receive vitamin D supplements, a tetanus booster shot, and monetary compensation up to $120 for completion of the study. If you do not complete the study, you will receive compensation at a rate of $15 per study visit completed.
What should I do if I have questions?
Call (530) 752-5177 and press #1