Vitamin D supplementation and bone mineral density - Women's Health - Author Abstract

Nutrition Research Newsletter, June, 2003

Bone mineral density (BMD) declines in women with the onset of menopause. There is both a reduction in the efficiency of absorption of calcium from the diet and an increased rate of bone resorption attributed to a decrease in serum estrogen, and the associated decrease in BMD may be accompanied by an increased risk of fracture due to minimal trauma. Studies have been reported in which additional calcium has been given by mouth in an attempt to overcome the negative calcium balance and reduce bone calcium loss. Variable results have been achieved with calcium supplementation, depending on concurrent dietary calcium intake, the number of years after menopause, the type of calcium used, and the bone site studied. The present study examined the effects of vitamin [D.sub.2] supplementation on changes in BMD in younger postmenopausal women who were also given 1000 mg Ca per day and compared those changes with the changes in BMD in women given 1000 mg Ca per day only.

Healthy white women who were postmenopausal by 1 to 10 years and who were not receiving hormone replacement therapy were recruited through media advertisements. In this two-year double blind, placebo-controlled study, all subjects received 1,000 mg Ca per day and were randomly assigned to receive either placebo or 10,000 IU vitamin [D.sub.2] once a week. At the beginning of the study, subjects were assessed by physical examination. Medical, social, dietary, and exercise histories were recorded, and subjects were advised to report any significant variations to lifestyle during the study. Blood and urine were collected for the measurement of variables to assess bone metabolism, and BMD was measured at six sites to assess appendicular as well as axial changes to the skeleton. Subjects were seen 1 month later to obtain blood for serum calcium and follicle-stimulating hormone measurement and then every six months for the duration of the study. At each of the six-month visits, relevant medical problems were recorded and investigated as necessary, blood and urine were collected, BMD measurements were performed, and treatment compliance was assessed by tablet counts and diary review.

When studied through the two-year studied period, the change in BMD at any of the sites studied did not differ significantly between subjects taking calcium supplements (Ca group) and subjects taking calcium and vitamin [D.sub.2] supplements (Ca+D group). The study found that there was no significant additional benefit to BMD in either the axial or appendicular skeleton of early postmenopausal women when vitamin [D.sub.2] in addition to calcium was given, rather than calcium alone. To sum it up, the present study failed to show any additional benefit in preservation of BMD in postmenopausal women when 10,000 U vitamin [D.sub.2] per week was added to daily calcium supplementation of 10(g) mg. The use of calcium alone over a two-year period was associated with no significant loss in BMD in the spine or femoral neck, a significant gain in BMD in the femoral trochanter and Ward's triangle, but a significant loss in BMD in the proximal radius and ulna.

L Cooper, P Clifton-Bligh, M Nery, G Figtree, S Twigg, E Hibbert, B Robinson. Vitamin D supplementation and bone mineral density in early postmenopausal women. AJCN (77[5]:1324-1329, May 2003). Correspondence: PB Clifton-Bligh, Northern Metabolic Bone Centre, Royal North Shore Hospital, St Leonards, NSW 2065, Australia. E-mail: pclifton@med.usyd.edu.au