Fitness and Health Characteristics in Conscripts With Supplementation of Vitamin D

Body mass (kg) and height (cm) is measured by the same person at the medical center using standardized equipment and the body mass index (BMI) is calculated in kg/m2.

Computed randomization is used to divide conscripts into two groups; either the intervention group or the control group. Both types of capsules are administered once per day in the morning before breakfast for 7 months. Standardized coded packages (3 per conscript) and capsules (100 per package) are manufactured on a special order by Innopharma A/S (Denmark). No commercial sponsoring is involved.

The key of the package code is stored in the computer database until unblinding of the results.

Laboratory measurements Serum samples for clinical chemistry analysis are collected into serum clot activator tubes. Calcium measurements are performed using spectrophotometry method. Ionized calcium measurements are performed using ion selective electrodes. The direct chemiluminescent immunoassay method is used for measurement of PTH. 25(OH)D is measured using direct chemiluminescent immunoassay method.

Power calculation The primary variable of the study is the level of 25 (OH)D in the serum. In the power analysis a difference of 20 nmol/L between the intervention and the control group is considered to be meaningful to detect. If the SD would be 25 nmol/L, then 26 participants would be needed in each group to reach a power of 80%.