Calcium absorption in normal and osteoporotic postmenopausal women

Summary Hourly fractional absorption of radiocalcium (alpha), serum calcitriol, and a number of other variables were measured in 152 normal and 148 osteoporotic postmenopausal women. Alpha, body weight, and serum albumin were all significantly lower in the osteoporotic than in the normal women, and plasma alkaline phosphatase, fasting urinary calcium, sodium, and hydroxyproline were all significantly higher in the osteoporotic than in the normal group. The most significant determinant of alpha in each group was the serum calcitriol concentration, but calcium absorption relative to serum calcitriol was significantly lower in the osteoporotic than in the normal women. The serum calcitriol level was slightly but not significantly lower in the osteoporotic than in the normal group and accounted for only 20% of the difference in alpha between them. The implied “resistance” to calcitriol in the osteoporotic group was significantly related to serum albumin and body weight but independent of age. Urinary hydroxyproline was an inverse function of alpha and a positive function of fasting urinary calcium in the osteoporotic group.     

Stone forming risk of calcium citrate supplementation in healthy postmenopausal women

PURPOSE: We evaluated the effect of calcium citrate supplementation alone or in combination with potassium citrate on the stone forming propensity in healthy postmenopausal women. MATERIALS AND METHODS: A total of 18 postmenopausal women without stones underwent a randomized trial of 4 phases comprised of 2 weeks of treatment with placebo, calcium citrate (400 mg calcium twice daily), potassium citrate (20 mEq twice daily), and calcium citrate and potassium citrate (at same doses). During the last 2 days of each phase urine was collected in 24-hour pools for complete stone risk analysis. RESULTS: Compared to placebo, calcium citrate increased urinary calcium and citrate but decreased urinary oxalate and phosphate. Urinary saturation of calcium oxalate, brushite and undissociated uric acid did not change. Potassium citrate decreased urinary calcium, and increased urinary citrate and pH. It decreased urinary saturation of calcium oxalate and undissociated uric acid, and did not change the saturation of brushite. When calcium citrate was combined with potassium citrate, urinary calcium remained high, urinary citrate increased even further and urinary oxalate remained reduced from the calcium citrate alone, thereby marginally decreasing the urinary saturation of calcium oxalate. Urinary pH increased, decreasing urinary undissociated uric acid. The increase in pH increased the saturation of brushite despite the decrease in urinary phosphorus. CONCLUSIONS: Calcium citrate supplementation does not increase the risk of stone formation in healthy postmenopausal women. The co-administered potassium citrate may provide additional protection against formation of uric acid and calcium oxalate stones.     

Diurnal variation of serum calcium and phosphorus in postmenopausal women

Summary Serum calcium, ionized calcium, and phosphorus have been obtained at hourly intervals in nine healthy postmenopausal women. The hourly means of ionized calcium and phosphorus demonstrate significant diurnal variation with a similar apogee, nadir, and periodicity (24 hours). These results are distinct from the diurnal variation of ionized calcium and phosphorus previously reported for young men and provide more evidence of an altered mineral hemostasis in postmenopausal women.     

Intestinal hyperabsorption of calcium and low bone turnover in hypercalciuric postmenopausal osteoporosis

Hypercalciuria of intestinal origin has been linked with bone loss in calcium nephrolithiasis and idiopathic osteoporosis. This retrospective data analysis was performed to explore potential pathogenetic link between intestinal hyperabsorption of calcium and postmenopausal osteoporosis. Data were retrieved from postmenopausal women who were evaluated for osteoporosis or osteopenia at the Mineral Metabolism Clinic of UT Southwestern Medical Center. A total of 319 patients underwent the test of calciuric response to oral calcium load to obtain an indirect measure of intestinal calcium absorption. Serum and urinary biochemistry and L2–L4 bone mineral density (BMD) were compared between five quintiles of calciuric response. There was a statistically significant trend toward a rise in 24-h urinary calcium and a decrease in urinary deoxypyridinoline (DPD) and BMD, with increasing order of quintiles. The presentation of those in the 1st quintile was consistent with vitamin D insufficiency or deficiency, with impaired calcium absorption, secondary hyperparathyroidism, and stimulated bone turnover (high normal urinary DPD). In contrast, patients in the 5th quintile displayed a picture of absorptive hypercalciuria of stone disease, with intestinal hyperabsorption of calcium, high or high normal urinary calcium and suppressed bone turnover (low or low normal urinary DPD). Thus, the assessment of intestinal calcium absorption in a seemingly homogeneous group of postmenopausal women with osteoporosis or osteopenia revealed a spectrum of calciuric response whose extremes may represent two physiologically distinct subtypes that have important diagnostic and therapeutic implications.     

Correlates of intestinal calcium absorption in women 10 years past the menopause

Summary Because intestinal calcium absorption may be an important independent determinant of calcium balance and therefore bone mass, we have studied this factor and other potential predictors in 196 healthy postmenopausal women. Gut calcium absorption was measured in each subject by a stable strontium method and expressed as a fractional absorption. The fractional absorption was significantly negatively correlated with years since menopause (YSM) (r=-0.15 P<0.05), and dietary calcium intake (r=-0.15 P<0.05), and significantly positively correlated with 24-hour urine calcium excretion (r=0.31 P<0.001) and body mass index (r=0.20 P<0.01). Apart from YSM, these factors remained as correlates in multiple regression analysis; the standardized regression coefficient was largest for 24-hour urine calcium excretion (0.32). Fractional absorption of calcium was not correlated with vertebral bone density. Thus, intestinal calcium absorption, although falling with increasing menopausal age and increasing calcium intake, is best correlated with the urine calcium excretion. This indicates either that gut calcium absorption is regulated in response to the magnitude of the urine calcium excretion or that the kidney maintains calcium balance by excreting what is absorbed by the intestine. The mechanisms whereby gut and renal calcium handling are correlated are uncertain.     

Vitamin D repletion does not alter urinary calcium excretion in healthy postmenopausal women

OBJECTIVE

To evaluate, in a posthoc analysis of a previous study, whether vitamin D repletion in postmenopausal women with insufficient vitamin D increases urinary calcium excretion, as vitamin D therapy might contribute to hypercalciuria and calcium stones in susceptible individuals, and the effect of vitamin D on the risk of urolithiasis warrants attention.

SUBJECTS AND METHODS

We recruited 18 women at ≥5 years after menopause who had vitamin D insufficiency (serum 25(OH)‐vitamin D, 16–24 mg/dL). We excluded women with a history of urolithiasis and kidney disease. Women had one calcium absorption study when vitamin D‐insufficient, received vitamin D therapy, and completed a second calcium absorption study when vitamin D‐replete. We fed subjects meals that mirrored the nutrient composition from self‐reported 7‐day diet diaries. To measure calcium absorption, we collected urine for 24 h during both visits.

RESULTS

We achieved vitamin D repletion in all women (25(OH)‐vitamin D before and after treatment, 22 and 63 mg/dL, respectively; P < 0.001). The mean calcium intake was 832 mg/day. Residual urine specimens were available for 16 women, allowing a measurement of 24‐h urinary calcium. Calcium excretion did not change after vitamin D therapy (212 before vs 195 mg/day after; P = 0.60). Of four women with hypercalciuria (>247 mg/day), calcium excretion decreased in three (377–312 mg/day, not significant).

CONCLUSION

Vitamin D supplementation did not increase the urinary calcium excretion in healthy postmenopausal women. Many stone formers are at risk of premature bone loss, vitamin D insufficiency, or both. Based on the present results we suggest a study of patients with hypercalciuria and nephrolithiasis to determine the risks of vitamin D therapy.     

Effects of nandrolone decanoate on forearm mineral density and calcium metabolism in osteoporotic postmenopausal women

Summary Although anabolic steroids have been used for many years to treat osteoporosis there is little available evidence about their efficacy or mode of action. These agents have recently been shown to produce an increase in total body calcium and bone density and it has been suggested that they stimulate bone formation. In this study 27 osteoporotic postmenopausal women were given 50 mg of nandrolone decanoate intramuscularly, every 2 or 3 weeks for 3 months, and the changes in forearm mineral density, fasting plasma, and urinary calcium, urinary hydroxyproline, and radiocalcium absorption were measured. Associated with a rise in forearm mineral density was a significant fall in fasting urinary calcium, but no significant change in fasting urinary hydroxyproline. The plasma calcium and phosphate fell significantly and there was a significant rise in the renal tubular reabsorption of calcium and a fall in the renal tubular reabsorption of phosphate. In a subset of 22 patients there was a significant rise in radiocalcium absorption. The results are consistent with the concept that nandrolone exerts a significant positive effect on bone formation and that this results in a fall in the fasting plasma calcium level, and consequently calcium excretion.     

The effect of an oral calcium load on plasma ionized calcium and parathyroid hormone concentrations in osteoporotic postmenopausal women

Summary Plasma ionized calcium (IC) and parathyroid hormone (PTH) concentrations were measured in 31 osteoporotic postmenopausal women at hourly intervals for 5 hours after a 1 g oral calcium load. Fifteen subjects had normal radiocalcium absorption and 16 subjects were malabsorbers of calcium. IC rose and PTH fell after the calcium load in both groups with a plateau at 3–4 hours, and the rise in IC was greater (P<0.01) in the normal absorbers. There was a nonsignificant trend for the fall in PTH to be greater in the normal absorbers. In the group as a whole the mean increase in IC (above baseline) at 4 hours was directly related to calcium absorption (P<0.025) and the mean change in PTH was inversely related to calcium absorption (P<0.05). These results demonstrate that in subjects with postmenopausal osteoporosis the responses of IC and PTH to an oral calcium load are a function of calcium absorptive status.     

Consumption of a high calcium mineral water lowers biochemical indices of bone remodeling in postmenopausal women with low calcium intake

Many postmenopausal women have a calcium intake far below the recommended amount and, in addition to attempting to improve their diet, need a calcium supplement. The aim of the study was to assess the effects of the consumption of a high calcium mineral water (HCaMW) on biochemical indices of bone remodeling in postmenopausal women with low Ca intake. A 6-month randomized double-blind placebo-controlled trial was designed to assess the effects of a daily consumption of 1 liter of a HCaMW (596 mg Ca/l) on serum parathyroid hormone (PTH) and biochemical markers of bone remodeling in postmenopausal women with a dietary Ca intake lower than 700 mg/day. The placebo group drank 1 liter of a mineral water with a low calcium content (10 mg/l). One hundred eighty healthy women were recruited (mean age: 70.1±4.0 years); 152 completed the 6-month trial. The changes from baseline of biochemical indices after 6 months consisted of a significant 14.1% decrease of serum PTH, osteocalcin (–8.6%), bone alkaline phosphatase (–11.5%), serum (–16.3%) and urine (–13.0%) type-1 collagen C-telopeptide in the HCaMW group compared to the placebo group, where all biochemical indices increased after 6 months. The additive effect of a small vitamin D supplement (400 iu/day) was also evaluated. In women receiving vitamin D in addition to HCaMW, the decrease in bone indices was not found to be greater than in women drinking only the HCaMW. A daily supplement of 596 mg of Ca through the consumption of 1 l of HCaMW was able to lower serum PTH and the indices of bone turnover in postmenopausal women with a low Ca intake. This could contribute to the repair of calcium deficiency and to the reduction of age-related bone loss in this population.This study was supported by a grant from Evian.     

Influence of age on effects of endogenous 1,25-dihydroxyvitamin D on calcium absorption in normal women

Recent reports of increases in serum 1,25-dihydroxyvitamin D [1,25(OH₂)D] concentration with aging despite no changes or decreases in calcium absorption suggest that elderly women have intestinal resistance to vitamin D action. Thus, in 15 young adult (30±1 year) and 15 elderly (74±1 year) women (mean±SE), we assessed the responsiveness of intestinal calcium absorption to increases in circulating 1,25(OH)₂D induced by 4 days of an experimental diet (150 mg calcium and 1600 mg phosphorus daily). True fractional calcium absorption (FCA) (⁴⁴Ca mixed with food and ⁴²Ca given intravenously, then their ratio in urine measured by mass spectrometry) was determined. Baseline serum intact parathyroid hormone (PTH) concentration was higher in the older women (P=0.01) whereas serum 1,25(OH)₂D concentration and true FCA were similar. In both groups, serum 1,25(OH)₂D concentrations increased (P<0.002) on the experimental diet. After 4 days on the diet, serum 1,25(OH)₂D increased over baseline by 30.5 and 35.6% and, despite these increases, true FCA was 40±3 versus 40±4%/24 hours (NS between groups) in the young and elderly women, respectively. These data suggest that either elderly women have normal intestinal responsiveness to vitamin D or that the resistance to it is too mild to be detected by these methods.     

Physical activity and dietary calcium interactions in bone mass in Scottish postmenopausal women

Summary  In this population-based cohort of 1,254 older Scottish women we found significant interactions between the mechanical component of self-reported habitual physical activity (PA) and dietary calcium (Ca) in BMD, independent of other risk factors. At low and/or medium Ca intakes BMD was higher amongst the most active people. Introduction  Although there is general agreement that increased activity (PA) and dietary calcium (Ca) consumption may help maintain bone mass in later life and prevent fractures, the amount required remains uncertain. Methods  In 2001–2003, 1,847 postmenopausal women (mean ± SD age: 69.3 ± 5.5 years) underwent bone mineral density (BMD) measurement and, in 2004, 68.7% (n = 1,254) completed a bone-specific Physical Activity Questionnaire (bsPAQ) and a food frequency questionnaire. The bsPAQ measures the metabolic and mechanical components of PA. Interactions of PA and Ca in BMD were examined using ANCOVA. Results  Significant interactions were identified in the BMD of the lumbar spine (LS), right hip (RH) and left hip (LH), after adjustment for confounders, between tertiles of PA classified according to the mechanical component and tertiles of energy-adjusted Ca intake (ANCOVA p = 0.006, p = 0.004 and p = 0.013 respectively). For example, at medium Ca intakes LH BMD was higher by 7.8% in the highest tertile of PA compared with the lowest tertile of PA. Conclusions  These data suggest that health promotion campaigns to increase PA would be most effective in populations with a low/medium calcium intake.     

Exercise frequency and calcium intake predict 4-year bone changes in postmenopausal women

The aim of this study was to examine the association of exercise frequency and calcium intake (CI) with change in regional and total bone mineral density (BMD) in a group of postmenopausal women completing 4 years of progressive strength training. One hundred sixty-seven calcium-supplemented (800 mg/day) sedentary women (56.1±4.5 years) randomized to a progressive strength training exercise program or to control were followed for 4 years. Fifty-four percent of the women were using hormone therapy (HT) at baseline. At 1 year, controls were permitted to begin the exercise program (crossovers). The final sample included 23 controls, 55 crossovers, and 89 randomized exercisers. Exercisers were instructed to complete two sets of six to eight repetitions of exercises at 70–80% of one repetition maximum, three times weekly. BMD was measured at baseline and thereafter annually using dual-energy X-ray absorptiometry. Four-year percentage exercise frequency (ExFreq) averaged 26.8%±20.1% for crossovers (including the first year at 0%), and 50.4%±26.7% for exercisers. Four-year total CI averaged 1,635±367 mg/day and supplemental calcium intake, 711±174 mg/day. In adjusted multiple linear regression models, ExFreq was positively and significantly related to changes in femur trochanter (FT) and neck (FN), lumbar spine (LS), and total body (TB) BMD. Among HT users, FT BMD increased 1.5%, and FN and LS BMD, 1.2% ( p <0.01) for each standard deviation (SD) of percentage ExFreq (29.5% or 0.9 days/week). HT non-users gained 1.9% and 2.3% BMD at FT and FN, respectively, ( p <0.05) for every SD of CI. The significant, positive, association between BMD change and ExFreq supports the long-term usefulness of strength training exercise for the prevention of osteoporosis in postmenopausal women, especially HT users. The positive relationship of CI to change in BMD among postmenopausal women not using HT has clinical implications in light of recent evidence of an increased health risk associated with HT.     

Effects of teriparatide on serum calcium in postmenopausal women with osteoporosis previously treated with raloxifene or alendronate

SUMMARY: The effect of teriparatide (20 microg/day) on serum calcium was examined in postmenopausal women previously treated with alendronate or raloxifene. Women previously treated with alendronate or raloxifene who added teriparatide or switched to teriparatide did not have clinically meaningful increases in mean predose serum calcium. INTRODUCTION: The effects of a 6-month treatment with teriparatide (20 microg/day; rhPTH(1-34), TPTD) on serum calcium (Ca) was examined in a prospective study of postmenopausal women previously treated with alendronate (70 mg/week or 10 mg/day [ALN] or raloxifene 60 mg/d [RLX]) for > or =18 months. METHODS: Women continued their usual ALN or RLX during a 2-month antiresorptive phase. Women previously treated with ALN were randomized to add TPTD (n = 52) or switch to TPTD (n = 50) and women previously treated with RLX were randomized to add TPTD (n = 47) or switch to TPTD (n = 49). All were to take at least 500 mg/day of elemental Ca and 400-800 IU/day of vitamin D. RESULTS: Predose mean serum Ca did not significantly change in groups adding TPTD to either RLX or ALN treatment. In patients who switched from RLX or ALN to TPTD, mean serum Ca increased by 0.05 mmol/L and 0.04 mmol/L respectively. Only 1 patient had the predefined calcium endpoint of serum calcium > 2.76 mmol/L (11 mg/dL) at more than one visit. CONCLUSIONS: Women previously treated with ALN or RLX who added TPTD or switched to TPTD did not have clinically meaningful increases in mean predose serum Ca.     

Estrogen replacement increased the citrate and calcium excretion rates in postmenopausal women with recurrent urolithiasis.

PURPOSE: Epidemiological data indicate a sharp increase in urinary calcium stone formation after menopause. We investigated the role of menopausal estrogen replacement therapy on the urinary constituents and characteristics that may influence recurrent calcium oxalate stone disease. MATERIALS AND METHODS: Urinary constituents in 28 postmenopausal women on estrogen replacement therapy for more than 6 months were compared with those in 41 women who had never been exposed to estrogen after menopause. These 2 groups had a history of recurrent calcium oxalate urolithiasis. A group of age matched, nonstone forming volunteers who were and were not on estrogen served as controls. RESULTS: The 24-hour urine collection revealed significantly higher mean calcium plus or minus standard deviation (188.8 +/- 101.5 versus 129.2 +/- 80.9 mg./24 hours, p <0.01), citrate (576.6 +/- 237.9 versus 306.2 +/- 209.9 mg./24 hours, p <0.001) and agglomeration inhibition (203 +/- 106 versus 159 +/- 81 minutes, p <0.05) in stone forming women who were versus were not on estrogen. CONCLUSIONS: Higher urinary citrate and higher agglomeration inhibition in women exposed to estrogen may decrease the risk of subsequent calcium stone formation.     

The role of skeletal calcium deficiency in postmenopausal osteoporosis

Summary A previous study of iliac crest composition identified skeletal calcium deficiency in 25% of 56 postmenopausal osteoporotic patients evaluated prior to the use of stanozolol or calcitonin. This report is a follow-up of biopsy data after 2 years of treatment with drug or placebo in 31 patients, 11 of whom had skeletal calcium deficiency. The study diet, consisting of 1 g elemental calcium plus 400 U Vitamin D, repaired the skeletal calcium deficiency in all patients, treated and untreated alike. Total body calcium (TBC) results were influenced by separation into calcium deficient and normal mineral groups, apparent treatment response being observed largely in patients with calcium deficiency. It is suggested that if all postmenopausal women ingested 1 g elemental calcium plus 400 U Vitamin D daily, skeltal calcium deficiency in osteoporosis would disappear as a problem. Meanwhile, it is important to recognize that repair of calcium deficiency is an important variable capable of influencing bone response to therapy and the evaluation thereof.     

Calcium bioavailability from heated oyster shell-seaweed calcium (active absorbable algae calcium) as assessed by urinary calcium excretion

The bioavailability of heated oyster shell-seaweed calcium (active absorbable algae calcium, AAA Ca) was compared to that of calcium carbonate by measuring increases of urinary calcium excretion after oral load. Eight normal male volunteers ingested 1000 mg calcium in the form of either calcium carbonate (CaCO₃) or AAA Ca in a crossover design with a 1-week interval between the two tests. The urinary calcium/creatinine (Ca/Cr) ratio was measured from 4h before to 6h after the administration at 2-h intervals. Urinary calcium excretion 4–6 h after oral ingestion of AAA Ca was 249 ± 119% (SD) of the baseline level, which was significantly higher than that after calcium carbonate, 170 ± 103% (SD) (P = 0.039). Paired comparison of the increment of urinary Ca/Cr over the pretest level was also significantly greater 4–6h after the ingestion of AAA Ca (0.21 ± 0.14) than that after calcium carbonate (0.132 ± 0.158) (P = 0.025). AAA Ca is thus suggested to be more biologically available than calcium carbonate in human subjects.     

Effect of gastric acid secretion on intestinal phosphate and calcium absorption in normal subjects

BACKGROUND.: Phosphate-induced hyperparathyroidism still represents an intriguingproblem in dialysis patients. Postprandial hyperphosphataemiais considered to be the main stimulus to parathyroid hyperfunction,and therefore many efforts have focused on the use of phosphatebinders to prevent phosphate absorption. METHODS.: We investigated whether the pH-mediated gastric ionization ofcalcium phosphate dietary salts is necessary for its intestinalabsorption. In eight normal subjects we measured 24-h urinarycalcium phosphate excretion and the postprandial blood calciumphosphate profile after a meal containing 1 g of calcium and2 g of phosphate salts in a crossover placeboomeprazole study.On two occasions the subjects received either placebo or omeprazole60 mg/day 2 days before and during the day test. RESULTS.: Serum gastrin levels were measured as an indicator of achlorhydriaand were 13.7 ± 1 pg/ml after placebo and 30.4 ±4.7 after omeprazole (P <0.003). Postprandial plasma phosphateprofiles were not significantly different between the two studies(+ 36 ± 8% after placebo and + 24 ± 8% after omeprazole,NS), while plasma calcium increased by + 6.1 ± 1% afterplacebo and decreased by – 4.2 ± 0.7% after omeprazole(P < 0.01). The 24-h urinary phosphate excretion was 1068± 85 mg after placebo and 773 ± 55 after omeprazole(P < 0.002), while the 24-h urinary calcium excretion was360 ± 21 after placebo and 238 ± 15 after omeprazole(P < 0.0001). A negative relationship was observed betweenabsolute changes in plasma gastrin and those in urinary calcium(P < 0.009) and phosphate (P < 0.05). CONCLUSIONS.: The inhibition of gastric acid secretion by omeprazole significantlyreduces both urinary phosphate and calcium excretion after anoral load. The behaviour of the postprandial calcium-phosphateplasma profile suggests that gastric acid inhibition is moreeffective in reducing calcium rather than phosphate dietarysalts absorption in normal subjects.     

Lactulose stimulates calcium absorption in postmenopausal women.

Animal studies have indicated that calcium absorption is increased by lactulose, a synthetic disaccharide. Therefore, the influence of lactulose on calcium absorption was measured in postmenopausal women who may benefit from the possible enhancing effect of lactulose on calcium absorption. Twelve postmenopausal women drank 100 ml of water containing 5 or 10 g of lactulose or a reference substance at breakfast for 9 days. The three treatments were given according to a randomized, double-blind, cross-over design, separated by two 19-day wash-out periods. On the 8th day of each treatment period, 44Ca dissolved in orange juice was drunk immediately after the solution with the study substance and just before a standard breakfast with 162 mg of carrier calcium. Within half an hour, 48Ca was given intravenously. Based on isotope ratios measured in urine collected before and until 36 h after isotope administration, true fractional calcium absorption was calculated. Calcium absorption during the treatments with the reference substance, 5 g and 10 g of lactulose was (mean +/- SD) 27.7 +/- 7.7, 30.0 +/- 7.6, and 32.2 +/- 7.0, respectively. A significant difference in calcium absorption was found between the highest dose of lactulose and the reference treatment (p < 0.01). A significant linear trend was found between the dose of lactulose and its positive effect on calcium absorption. In conclusion, in postmenopausal women a 9-day consumption of lactulose increases calcium absorption in a dose-response way. More research is warranted to explore how lactulose stimulates calcium absorption and whether it is able to improve calcium balance and/or to attenuate the rate of aging bone loss.     

LCT 13910 C/T polymorphism, serum calcium, and bone mineral density in postmenopausal women

Summary  LCT 13910 CC genotype is associated with lactose intolerance, a condition often resulting in reduced milk intake. Women with the CC genotype were found to have decreased serum calcium and reduced bone mineral density. Introduction  The CC genotype of the 13910 C/T polymorphism of the LCT gene is linked to lactose intolerance and low calcium intake. Methods  We studied 595 postmenopausal women, including 267 osteoporotic, 200 osteopenic, and 128 healthy subjects. Genotyping, osteodensitometry, and laboratory measurements were carried out. Results  Frequency of aversion to milk consumption was 20% for CC genotype and 10% for TT + TC genotypes (p = 0.03). The albumin-adjusted serum calcium was 2.325 ± 0.09 mmol/L for CC genotype and 2.360 ± 0.16 mmol/L for TT + TC genotypes (p = 0.031). Bone mineral density (BMD; Z score) was lower in the CC than TT + TC genotypes, respectively, at the radius (0.105 ± 1.42 vs 0.406 ± 1.32; p = 0.038), at the total hip (−0.471 ± 1.08 vs −0.170 ± 1.09; p = 0.041), and at the Ward’s triangle (−0.334 ± 0.87 vs −0.123 ± 0.82; p = 0.044). Conclusion  LCT 13910 C/T polymorphism is associated with decreased serum calcium level and lower BMD in postmenopausal women. Péter Lakatos and Gábor Speer contributed equally to this work.     

The relationship of sodium intake to calcium and sodium excretion and bone mineral density of the hip in postmenopausal African-American and Caucasian women

During the past several decades in the United States, there has been a shift in dietary habits, with an increased consumption of processed foods that are high in sodium. It is known that calcium and sodium metabolism are linked and that higher sodium intakes may increase calcium excretion. Epidemiological studies in patients with idiopathic hypercalciuria suggest that hypercalciuria is linked to low bone mass. However, the relationship of sodium intake to bone mineral density (BMD) is controversial in Caucasians and has not been explored in African-Americans. To determine the consequences of sodium intake on bone in African-American and Caucasian postmenopausal women, sodium and calcium excretion and BMD of the total hip were measured in 50 Caucasian and 39 African-American postmenopausal women. After adjustment for race and urine volume, sodium excretion was a significant predictor of calcium excretion (P 0.01). This relationship was modulated by calcium intake (P 0.01), but not by race (P = 0.63). There was no significant effect of sodium excretion (P = 0.42) or calcium excretion (P = 0.90) on BMD of the total hip after adjusting for race and urine volume. Sodium excretion is a significant predictor of calcium excretion in both postmenopausal African-American and Caucasian women. The relationship between sodium and calcium excretion is modulated by calcium intake, and the relationship is strongest at low calcium intakes (1000mg/day). However, sodium excretion in the range of 53.75–283.33mmole/g/total volume (mmole/g/TV) is not a significant predictor of total hip BMD in elderly African-American and Caucasian postmenopausal women.