(HealthDay News) – Vitamin D supplementation alone does not improve bone health in postmenopausal women, but calcium alone or in combination with vitamin D does appear to reduce bone turnover, according to a study published online Sept. 24 in the Journal of Clinical Endocrinology & Metabolism.

John F. Aloia, M.D., from Winthrop University Hospital in Mineola, NY, and colleagues randomly assigned 159 postmenopausal healthy, white women to receive double placebo; calcium (1,200mg daily) plus placebo; vitamin D3 (100µg) plus placebo; or vitamin D3 and calcium. At baseline and at three and six months, serum and urine were collected fasting and two hours after a calcium load.

The researchers found that, before study medication, a calcium load resulted in a decline in parathyroid hormone (PTH) and C-telopeptide (CTX) and an increase in urinary calcium excretion. With calcium supplementation, serum CTX and procollagen type I N-terminal propeptide declined over time, but did not change with increased vitamin D intake. In the vitamin D groups there was a decline in PTH in the fasting state, compared with placebo. After a calcium load in the vitamin D groups, suppression of PTH was greater. Urinary calcium was raised and PTH and CTX were decreased with a calcium load.

“Supplementation of the diet with 1200mg calcium/d reduces bone turnover markers, whereas supplementation with up to 100 µg vitamin D3/d does not,” the authors write.

The study was partially funded by Merck.

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