Effect of Calcium Supplement Particle Size and Vitamin D Supplement on Calcium Retention in Adolescent Girls

An important strategy to reducing the risk for osteoporosis and fracture in later life is to
optimize the development of peak bone mass during adolescence. Because calcium is the main
mineral component of bone, maximizing calcium absorption and retention during adolescence is
important to maximize peak bone mass.

Our two research arms address two different mechanisms by which calcium absorption and
retention may be increased:

1. We hypothesize that a smaller particle size calcium carbonate supplement (than that
which is now commercially available) may be better absorbed and lead to higher calcium
retention in adolescents.

2. We hypothesize that vitamin D supplementation will increased calcium absorption and
retention in adolescents.

Subjects will be assigned to one of the two research arms.

1)Small and large particle size calcium supplements or placebo or 2) calcium supplements with
or without vitamin D supplements will be given to subjects during two 3-week study periods in
which subjects live on-site.

Calcium absorption will be measured by parathyroid hormone suppression after a calcium load
and by stable calcium isotope in some subjects.

Calcium retention will be measured by calcium intake minus calcium excretion.

Inclusion Criteria:

- 12-14 year old girls

- Generally Healthy

Exclusion Criteria:

- History of alcohol, smoking, or non-prescription drug use

- Malabsorptive disorders, bone, liver, or kidney disease that may affect calcium
metabolism

- Oral contraceptive use

- Pregnancy