Search:
Menopause Live - IMS Updates
InFocus

Date of release: 02 March, 2009

Dietary calcium and serum 25-hydroxyvitamin D status in relation to bone mineral density


Considerable uncertainty exists regarding optimal intakes of calcium. This is reflected in markedly different recommended daily intakes in various countries [1]. A recent paper reports a study which was carried out in the United States among 4958 community-dwelling women and 5003 men aged 20 years or more [2]. According to the results, a higher calcium intake was significantly associated with higher bone density (p value for trend = 0.005) only for women with serum 25-hydroxyvitamin D [25(OH)D] status below 50 nmol/l. Among men, there was no significant association between a higher calcium intake beyond the upper end of the lowest quartile (626 mg/day) and bone density within all 25(OH)D categories. Among both genders, bone density increased stepwise and significantly with higher 25(OH)D concentrations(< 50 nmol/l, 50–74 nmol/l, ≥ 75 nmol/l); for women, the p value for trend was < 0.0001, and for men, p = 0.0001.

Comment

Calcium is a structural component of bone. Calcium supplementation may improve bone density and reduce fractures by suppressing parathyroid hormone secretion and thus reducing bone resorption [3]. In fact, a meta-analysis has shown that calcium supplementation of 500–2000 mg/day in postmenopausal women provided a modest benefit on bone density: 2.05% difference in total body bone density, 1.66% for the lumbar spine and 1.64% for the hip [4]. However, the effects of calcium supplementation on bone mineral density appear to represent a one-time increment that does not continue to accrue with time [5], and the implications for fracture risk prevention of such small differences are unclear.
 
This study has shown that, among men and women, 25(OH)D status appears to be the dominant predictor of bone density relative to calcium intake. Only women with 25(OH)D concentrations below 50 nmol/l appear to benefit from a higher calcium intake. Therefore, the findings of this study add support to the concept that the correction of 25(OH)D status is more important than increasing dietary calcium intake beyond 566 mg/day for women and 626 mg/day among men for better hip bone density. A higher calcium intake beyond 566 mg/day may only be important for women with 25(OH)D concentrations below 50 nmol/l, while, for women with higher 25(OH)D concentrations, hip bone density is not correlated with calcium intake.

Comentario

Mark P. Brincat
Department of Obstetrics and Gynaecology, Mater Dei Hospital, BKara Bypass, Malta

Jean Calleja-Agius
Department of Obstetrics and Gynaecology, Mater Dei Hospital, BKara Bypass, Malta

    References

  1. Feskanich D, Willett WC, Stampfer MJ, Colditz GA. Milk, dietary calcium, and bone fractures in women: a 12-year prospective study. Am J Public Health 1997;87:992-7.
    http://www.ncbi.nlm.nih.gov/pubmed/9224182

  2. Bischoff-Ferrari HA, Kiel DP, Dawson-Hughes B, et al. Dietary calcium and serum 25-hydroxyvitamin D status in relation to bone mineral density among US adults. J Bone Miner Res 2008;Dec 29 [Epub ahead of print].
    http://www.ncbi.nlm.nih.gov/pubmed/19113911

  3. Blumsohn A, Herrington K, Hannon RA, Shao P, Eyre DR, Eastell R. The effect of calcium supplementation on the circadian rhythm of bone resorption. J Clin Endocrinol Metab 1994;79:730-5.
    http://www.ncbi.nlm.nih.gov/pubmed/8077353

  4. Shea B, Wells G, Cranney A, et al. Meta-analyses of therapies for postmenopausal osteoporosis. VII. Meta-analysis of calcium supplementation for the prevention of postmenopausal osteoporosis. Endocr Rev 2002;23:552-9.
    http://www.ncbi.nlm.nih.gov/pubmed/12202470

  5. Bischoff-Ferrari HA, Dawson-Hughes B, Baron JA, et al. Calcium intake and hip fracture risk in men and women: a meta-analysis of prospective cohort studies and randomized controlled trials. Am J Clin Nutr 2007;86:1780-90.
    http://www.ncbi.nlm.nih.gov/pubmed/18065599