A Randomized Double-blind Placebo-controlled Trial of the Effect of Vitamin D Supplementation on Breast Density in Premenopausal Women
- to determine whether adding oral supplementation with vitamin D3 (cholecalciferol) at
doses of 1,000, 2,000 and 3,000 IU/d to baseline total vitamin D intake over a period of 12
months reduces mammographic breast density among premenopausal women at moderate to high
risk of breast cancer who reside in the Quebec City area, Canada.
- to assess the net increase in 25(OH)D levels resulting from this vitamin D3
- to document the compliance with, and safety of, supplementation with tested doses of
vitamin D3 over one year.
OUTLINE This study is a double-blind, placebo-controlled, randomized trial among
premenopausal women who live in the Quebec City area and have ≥ 20% breast density at
The intervention consists of the addition, over baseline total vitamin D intake from food
and supplements, of three different doses of vitamin D3 (1000, 2000 or 3000 IU/day) for a
period of 12 months. There are four arms in the trial:
- Arm 1: 1,000 IU vitamin D3/d (1 tablet vitamin D 1000 IU + 2 tablets placebo);
- Arm 2: 2,000 IU vitamin D3/d (2 tablets vitamin D 1000 IU + 1 tablet placebo);
- Arm 3: 3,000 IU vitamin D3/d (3 tablets vitamin D 1000 IU);
- Arm 4: placebo (3 tablets placebo/d).
Vitamin D tablets (1000 IU tablets) and the placebo tablets are undistinguishable in size,
shape, color and taste, and are manufactured by the same company.
Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor), Primary Purpose: Prevention
Mammographic breast density
Difference in breast density between baseline and at 12 months
Jacques Brisson, M.D., Sc.D.
Centre de recherche du CHU de Québec, et Faculté de médecine de l'Université Laval
Canada: Health Canada