Context: Effects of long term calcium with or without vitamin D on hip bone mineral density and bone turnover in sunny climates have not been reported.

Objective: Evaluation of vitamin D added to calcium supplementation on hip DXA BMD and calcium related analytes.

Design, setting and participants: A five-year randomised controlled double-blind trial of 120 community-dwelling women aged 70–80 years.

Interventions: Calcium 1200 mg/d with placebo (Ca group) or 1000 IU/d vitamin D2 (CaD group), or double placebo (control).

Main outcome measures: Hip BMD, plasma 25OHD, biomarkers of bone turnover, PTH and intestinal calcium absorption.

Results: Hip BMD was preserved in CaD (-0.17%) and Ca (0.19%) groups but not controls (-1.27%) at year one and only maintained in the CaD group at years 3 and 5. The beneficial effects were mainly in those with baseline 25OHD levels below the median (68 nmol/L). At year one, compared with controls, Ca and CaD groups had 6.8% and 11.3% lower plasma alkaline phosphatase, respectively (P 0.02), and 28.7% and 34.5% lower urinary DPD/Cr ratio, respectively (P 0.05). At 5 years, this suppression was only maintained in the CaD group. CaD reduced PTH at 3 and 5 years cf controls (27.8 and 31.3%, P 0.005) in those with baseline PTH levels above the median (3.6 pmol/L). Therapy did not affect intestinal calcium absorption at high carrier loads.

Conclusions: Addition of vitamin D to calcium has long term beneficial effects on bone density in elderly women living in a sunny climate, probably mediated by a long term reduction in bone turnover rate.