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United States Department of Agriculture

Agricultural Research Service

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Vitamin D Supplementation and Immune Function Study for Men and Women


USDA, ARSWesternHumanNutritionResearchCenter invites healthy men and women, ages 20 - 49 years (men) or 20-45 years (women), to participate in a 12 week study with nine study visits on the UC Davis campus or at Ticon-1 at UCDMC.


Who is conducting this study?


Charles B. Stephensen, PhD from the USDA, ARS, WesternHumanNutritionResearchCenter is conducting this study. The study has been reviewed and approved by the UC Davis Committee for the Protection of Human Studies. There is only minimal health risk associated with participation in this study.


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 Sacramento for 1 screening and 8 study visits, some of which require blood draws. Volunteers must have a Body Mass Index (BMI) between 18.5-30 kg/m2. Volunteers must not be consuming vitamin D supplements. Potential volunteers must be willing to take daily pills for 12 weeks that contain 400 International Units (IU), 2,000 IU, or 5,000 IU of vitamin D.


Who is NOT eligible to participate?


Adults who:

  • 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, 2000 Stockton Blvd. at UCDMC in Sacramento. This visit will require fasting for 12 hours. You will give your written informed consent to participate in the study. We will record your age, weight and height; blood pressure, heart rate and body temperature. We will collect a small blood sample, 20 mL (4 teaspoons), which will be used to determine if you have anemia, to rule out liver or kidney disease, and to check your vitamin D status. This visit will take about 30 minutes. If your serum Vitamin D level is less than 25 nmol/L, you will not qualify and will be informed by mail and provided information about risks of deficiency and how to increase vitamin D intake. If your serum Vitamin D level is greater than 50 nmol/L, you will not qualify and will be informed by mail.


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

Last Modified: 8/13/2016
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