Background – Postmenopausal women are at increased risk of secondary hyperparathyroidism resulting in reduction in bone mass because of loss of the beneficial effects of estrogen on stimulation of intestinal calcium absorption and reduction of renal calcium excretion.
Objective – To evaluate the relative benefits of vitamin D and calcium supplementation compared to calcium alone on hip bone mineral density (BMD) in ambulant elderly Western Australian women aged 70-80 years at baseline. Design – A 5-year randomised controlled double-blind study of 40 women per group assigned to received either 1000 IU vitamin D and 1200 mg calcium carbonate (CaD group), 1200 mg Ca and placebo vitamin D (Ca group) or placebo Ca and placebo vitamin D (placebo group) per day over the 5 years. Hip BMD was measured by DXA at baseline and years 1, 2, 3 and 5 using an identical protocol. Vitamin D status was measured at baseline.
Outcomes – The mean baseline age of subjects was 74.5 ± 2.4 years, mean total hip DXA 817 ± 99 mg/cm2 and mean total 25(OH)D 68.0 ± 28.7 nmol/L, 43% had vitamin D insufficiency (25(OH)D < 60 nmol/L), there were no baseline differences between the groups. Adjusted for baseline values, both Ca and CaD groups had significantly better maintenance of hip structure than the placebo group at 1 year, the effects were maintained in the CaD group at 3 and 5 years.Conclusions – Addition of vitamin D to calcium may have long term beneficial effects on bone structure in elderly postmenopausal Australian populations on the 35th parallel South.