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The objective of this study is to examine the effect of milk powder supplementation with different calcium contents on bone mineral density (BMD) in postmenopausal Chinese women, and to determine a more appropriate dose of calcium supplementation. A 2-year, randomized controlled double-blind trial. Postmenopausal women (n = 210) aged 50-65 years were recruited and assigned randomly into three calcium supplementation groups. All participants received milk powder supplementation with different calcium contents (300, 600, and 900 mg per day for groups A, B, and C, respectively) and all groups received 800 IU of vitamin D per day. During the follow-up period, BMD of the left hip and lumbar spine (as the main indicator) was measured using dual-energy X-ray absorptiometry at the baseline, 1 and 2 years. Both three BMD measures and the changes of BMD over 2 years were used to analyze. Before adjusting for covariates, BMD in group A of the lumbar spine and groups A and B of greater trochanter decreased significantly from the baseline over time but increased significantly in the rest groups of the lumbar spine and greater trochanter and in three groups of Ward's triangle. There were significant differences across the three groups for changes of BMD in the greater trochanter and Ward's triangle. When adjusting for covariates, there were significant decreases with time in group A of the spine (P = 0.001), groups A and B of greater trochanter (P = 0.0002 and P = 0.04, respectively) and increases in groups B and C of Ward's triangle (P = 0.03 and P = 0.004, respectively). BMD change in the greater trochanter was significantly different among three groups. For healthy postmenopausal women, high calcium milk powder supplementation was better in retarding bone loss than medium and low calcium in the greater trochanter. Considering the dietary calcium intake of postmenopausal women in north of China, a dose of 900 mg/day is considered as the most appropriate calcium supplementation for greater trochanter but not for other sites. [ABSTRACT FROM AUTHOR]

We compared the effects of oral calcium and vitamin D separately and together on relevant variables in 22 postmenopausal volunteers with initial serum 25OHD levels below 60 nmol/L. Subjects were allocated randomly to two regimens: group 1 received 1 week of calcium 1,000 mg, followed by 7 weeks with additional vitamin D3 1,000 i.u. daily; group 2 received 7 weeks of D3 1,000 i.u. daily, followed by 1 week with additional calcium 1,000 mg. We measured serum calcium, phosphate, PTH, 25OHD, CTX, and ALP at baseline and after 1 and 8 weeks in group 1 and after 7 and 8 weeks in group 2. There were no significant changes in ALP from either vitamin D or calcium. Calcium caused significant elevation of serum 25OHD as well as major suppression of serum CTX, which could not easily be accounted for by suppression of PTH. Vitamin D caused no significant change in any variable except elevation of serum 25OHD. The suppressive effect of calcium (whether given first or second) on serum CTX was threefold greater than that of vitamin D (whether given first or second) (P < 0.001), although their suppressive effects on serum PTH were the same. Calcium and vitamin D yielded greater and more significant effects on all variables (except ALP) than either treatment alone. We suggest that calcium may elevate serum 25OHD by prolonging its half-life and that it may have an inhibitory effect on bone resorption independent of, or in addition to, its suppression of PTH. [ABSTRACT FROM AUTHOR]

In rat intestine, the 9 kilodalton calbindin (CaBP9K) is significantly increased in vivo by 1,25-dihydroxyvitamin D3 (1, 25(OH)2D3) through a vitamin D (D) response element located in the 5'-flanking region of the gene. However, in vitro calcium has also been reported to increase CaBP9K gene expression in fetal duodenal culture preparations. The aim of the studies was to investigate whether calcium feeding alone can influence CaBP9K gene expression in vivo in adult rat duodena by evaluating the pattern of expression of its mRNA following short- or long-term exposure to oral calcium, comparing the data to exposure to the known inducer of the gene, 1, 25(OH)2D3. Hypocalcemic D-depleted rats were acutely or chronically supplemented with calcium per os, or with 1,25(OH)2D3 in the presence or absence of oral calcium. Short-term calcium feeding was shown to significantly increase the expression of the CaBP9K gene to a level similar to that observed in 1,25(OH)2D3-treated rats but no additive effect between oral calcium and 1,25(OH)2D3 on the level of its mRNA was observed. Moreover, the calcium effect on CaBP9K gene expression was shown to be independent of the circulating ionized calcium concentration and, contrary to the effect of 1,25(OH)2D3, not sustained following long-term exposure. Our data clearly indicate that oral calcium alone has a significant but only transient effect of the expression of the adult rat intestinal CaBP9K gene in vivo and that maintenance of its expression requires normalization of the D endocrine system. [ABSTRACT FROM AUTHOR]

The biochemical effects of a single oral dose of 10 mmol of calcium on certain blood and urine variables were studied in 20 elderly postmenopausal subjects (mean age 72.3±6.2 years) with a very low dietary calcium intake (mean 7.2±3 mmol/day). Twelve hours after calcium administration, the plasma total calcium, phosphate and bicarbonate, and the urinary calcium/creatinine ratio rose, while the plasma parathyroid hormone and chloride, and urinary hydroxyproline/creatinine and phosphate/creatinine ratios fell. These results show that a single oral dose of calcium suppresses bone resorption in elderly women with low dietary calcium intake, and that long-term supplementation may be important in the prevention of osteoporosisrelated fractures. [ABSTRACT FROM AUTHOR]

We have previously shown that a calcium (Ca) supplement of 1000 mg given in the evening reduces the overnight and early morning, but not the daytime, excretion of bone resorption markers in postmenopausal women within five years of the menopause. In the present study, we have looked at the effect of splitting the Ca into two doses of 500 mg each given in the morning and evening. We studied 19 healthy women (median age 53 years) who were all within 5 years of the menopause. On the 2 study days, urine was collected from 9 a.m. to 9 p.m. (day collection), and from 9 p.m. to 9 a.m. (night collection); a further fasting (spot) urine sample was obtained at 9 a.m. at the end of the night collection. The first day was a control day; on the second day the subjects ingested 500 mg Ca as the carbonate at 9 a.m. and 9 p.m. We measured pyridinoline cross-links excretion in all the samples, as well as hydroxyproline in the fasting urine. The Ca supplements lowered urinary excretion of the markers during the day (P < 0.01), had only a marginal effect during the night, but reduced excretion significantly in the fasting urine (P < 0.001). In the whole 24-hour period, the falls in resorption markers were small but comparable to those seen after the ingestion of 1 g of Ca in the evening. We conclude that the acute administration of 0.5 g Ca in the morning and evening reduced the markers of bone resorption in early postmenopausal women during the day but not during the following night, whereas the single 1 g supplement had the reverse effect. Over the 24-hour period, there was nothing to choose between the two regimes. Women at this stage in their life cycle probably require a larger Ca supplement if they are not taking estrogen. [ABSTRACT FROM AUTHOR]