Acute effect of a supplemented milk drink on bone metabolism in healthy postmenopausal women is influenced by the metabolic syndrome

Background

Dietary factors acutely influence the rate of bone resorption, as demonstrated by changes in serum bone resorption markers. Dietary calcium exerts its effect by reducing parathyroid hormone levels while other components induce gut incretin hormones both of which reduce bone resorption markers. The impact of dietary calcium on bone turnover when energy metabolism is modulated such as in metabolic syndrome has not been explored. This study was designed investigate whether metabolic syndrome or a greater amount of visceral fat influences the impact of dietary calcium on bone turnover.

Methods

The influence of the metabolic syndrome on effects of dietary calcium on bone turnover in community dwelling postmenopausal women was studied. Twenty five volunteers consumed 200 mL of low fat milk with additional 560 mg calcium (one serve of Milo®) in the evening on one occasion. Fasting morning serum biochemistry before and after the milk drink with lumber spine bone density, bone mineral content, fat and lean mass using dual energy X-ray absorptiometry (DXA) and waist circumference were measured. The women were divided into 2 groups using the waist measurement of 88 cm, as a criterion of metabolic syndrome. Student’s t tests were used to determine significant differences between the 2 groups.

Results

The lumbar spine mineral content was higher in women with metabolic syndrome. After consuming the milk drink, serum bone resorption marker C terminal telopeptide (CTX) was suppressed to a significant extent in women with metabolic syndrome compared to those without.

Conclusions

The results suggests that dietary calcium may exert a greater suppression of bone resorption in post-menopausal women with metabolic syndrome than healthy women. Despite substantial evidence for close links between energy metabolism and bone metabolism this is the first report suggesting visceral fat or metabolic syndrome may influence the effects of dietary calcium on bone metabolism.

Suppression of parathyroid hormone and bone resorption by calcium carbonate and calcium citrate in postmenopausal women

This study was conducted to compare the suppressive effects of calcium carbonate and calcium citrate on bone resorption in early postmenopause. Calcium citrate is thought to be better absorbed. We therefore tested the hypothesis that calcium as citrate is more effective than calcium as carbonate in suppressing parathyroid hormone (PTH) and C-terminal telopeptide. Twenty-five healthy postmenopausal women were recruited in this double blind crossover study. The subjects were randomly allocated to receive either 1,000 mg of elemental calcium as carbonate or 500 mg of calcium as citrate. They were given the alternate calcium dose 1 week later. Serum measurements of total and ionized calcium, phosphate, PTH, and CrossLaps were repeated 12 hours after each dose. Analysis of variance found no significant difference between measures for the two salts. Tests for equivalence indicated that 500 mg of calcium citrate may be superior to 1,000 mg of calcium carbonate in raising serum total and ionized calcium (P = 0.04 and 0.05, respectively). For all parameters measured, 500 mg of calcium citrate was at least as beneficial as 1,000 mg of calcium carbonate. Calcium citrate is at least as effective as calcium carbonate in suppressing PTH and C-terminal telopeptide cross-links, at half the dose. This may be because calcium as citrate is better absorbed than calcium as carbonate. If calcium citrate can be used in lower doses, it may be better tolerated than calcium carbonate.