ORIGINAL COMMUNICATION

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1 (2004) 58, & 2004 Nature Publishing Group All rights reserved /04 $ ORIGINAL COMMUNICATION Calcium and vitamin D 3 supplements in calcium and vitamin D 3 sufficient early postmenopausal healthy women J Tfelt-Hansen 1 and O Tørring 1,2 * 1 Department of Endocrinology PE, Copenhagen University Hospital, Rigshospitalet, Denmark; and 2 Division of Endocrinology, Department of Medicine and Karolinska Institutet at Södersjukhuset, Stockholm, Sweden Objective: To study the calcium homeostasis in healthy, calcium and vitamin D replete early postmenopausal women during oral supplementation with calcium and vitamin D 3. Design: A prospective, placebo-controlled, randomised, double-single-blind, 3-week study. Setting: Outpatient clinic at Copenhagen University Hospital, Denmark. Subjects: In all, 17 started, one was excluded. Totally, 16 healthy women, y of age (mean 57.3 y) who were at least 4 y after menopause (mean 6.7 y) completed. Interventions: All underwent three consecutive 7-day study periods. Each began with 4 days of normal diet followed by 3 days treatment of either C: one tablet of mg calcium carbonate (ie 500 mg Ca 2 þ per tablet) twice daily (breakfast and dinner), or CD 3 : as in C but plus 400 IU vitamin D 3 b.i.d., or P (only) placebo tablets b.i.d. Results: At baseline plasma 25-hydroxycholecalciferol was normal (66722 nmol/l) and the calcium intake without supplements 850 mg/day. In group C, the 24-h urinary calcium increased by 35% ( mmol), vs the placebo group P ( mmol) (Po0.05). Addition of 800 IU vitamin D 3 daily (CD 3 ) did not increase calcium excretion further ( mmol) but decreased plasma 1,25-(OH) 2 -vitamin D 3 by 21% (Po0.05). Conclusions: In this carefully controlled study calcium plus vitamin D 3 supplements only had minor influences of uncertain significance on the calcium balance in healthy, calcium and vitamin D sufficient early postmenopausal women. Sponsorship: Copenhagen University, Karolinska Institutet and Nycomed A/S. (2004) 58, doi: /sj.ejcn Published online 28 April 2004 Keywords: calcium metabolism; vitamin D; postmenopausal women; cholecalciferol; Ca 2 þ ; 1,25(OH) 2 D 3 ; PTH Introduction Adequate intakes of calcium and vitamin D are essential for skeletal growth and prevention of osteoporosis. A considerable number of elderly women, however, have biochemical indications of calcium and vitamin D deficiency (Lips, 1991; McKenna, 1992; Melin et al, 1999). Supplements may improve calcium balance, prevent secondary hyperparathyroidism, postpone bone loss and reduce the risk of osteoporotic *Correspondence: Dr O Tørring, Chief of Division of Endocrinology, Department of Medicine, C7, Karolinska Institutet, Södersjukhuset, S Stockholm, Sweden. ove.tørring@sos.sll.se Guarantor: O Tørring. Sources of support: Nycomed DK-4000 Roskilde, Denmark Received 7 May 2003; revised 9 March 2004; accepted 16 March 2004; published online 28 April 2004 fractures (Aida et al, 1995; Chapuy et al, 1992, 1994; Francis et al, 1996; Ooms et al, 1995;Tilyardet al, 1992).Postmenopausal women without hormone replacement therapy are recommended daily dietary intakes of mg calcium and 800 IU vitamin D, recommendations that may be difficult to be met with a normal diet (NIH Consensus Statement, 1994; Physician s guide to prevention and treatment of osteoporosis, 2000; Rasmussen et al, 2000). Many women therefore start taking calcium and vitamin D 3 supplements soon after the menopause in order to prevent early osteoporosis. During the first 2 4 y after menopause, these supplements, however, have no significant effect on bone mass mainly due to an increased bone turnover and net output of calcium from the skeleton caused by diminishing oestrogen concentration (Dawson- Hughes et al, 1990). The question is does vitamin D supplementation have any advantage over calcium supplementation

2 in healthy, calcium- and vitamin D-sufficient early postmenopausal women with regard to calcium homeostasis? Commercial calcium supplements are available as various salts, for example, carbonate, phosphates, citrate and bone powder. Bioavailability of calcium is between 20 and 40% in these supplements and varies with the salt and the formulation. Bioavailability is approximately 32 35% for calcium carbonate, which is the most frequently used source of calcium and the most cost effective, containing 40% Ca 2 þ (Heaney et al, 1990). Calcium balance can be estimated with various methods: determination of oral intake minus combined urinary, fecal and dermal losses, with radioactive or stable isotopic tracer or by metabolic changes after oral calcium load (Zerwekh et al, 1981). The first method is cumbersome and not very precise. Isotopic tracers are restricted in use in Denmark due to legislation. Whenever a calcium supplement is investigated in short-term studies, metabolic methods such as urine calcium excretion and changes in plasma PTH are therefore preferred (Tørring et al, 1985; Tfelt-Hansen et al, 2001). In the present study, 24 h urinary calcium excretion was used as indicator of calcium absorption in the group of healthy, early postmenopausal women consuming an omnivorous diet and having normal plasma 25-hydroxy-cholecalciferol (25(OH)D 3 ). Subjects and methods Subjects In all, 17 women were included of which one was erroneously randomized since her hypertension was overseen. She therefore was excluded from the study. Totally, 16 healthy women completed the study. Mean age was y (52 61 y), mean body weight kg (55 94 kg) and mean Body mass index kg/m 2. Years after menopause (last period) was y (mean7s.d.) (range 4 11 y). All participants were recruited through announcements on bulletin boards and in the newsletter of the hospital or among the hospital staff or their friends and all had some connection with the healthcare system and were familiar with collection of urine, diet control etc. The inclusion criteria were: Signed informed consent, female, age y, with menopause 4 y prior and a normal, common Danish diet (omnivorous). Exclusion criteria included significant diseases including hypertension, treatment with corticosteroids, hormone replacement therapy, intake of drugs known to influence calcium metabolism, current use of supplements with calcium and/or vitamin D 3 (4200 IU/day), coffee consumption above 1 l daily and a dietary calcium intake below 600 mg daily. Diet At 1 3 weeks before inclusion, all subjects were interviewed by an certified and experienced dietician about their diet and intake of calcium and vitamin D. They were instructed to keep a normal diet with a calcium intake of mg daily. The mean calcium intake was mg at screening and mg at entry. Three subjects increased their calcium intake to comply with the entry criterion and six reduced. The dietary vitamin D intake was judged by our dietician after interviewing each subject to be normal in all which is also reflected in normal baseline 25(OH)-vitamin D 3 levels (Table 2). Study design and test treatment Placebo-controlled, randomized, double-single blind and cross-over with three test treatments: 1. Calcium (C): 500 mg calcium tablets (as mg CaCO 3, Calcium s chewable tablets, Nycomed, Denmark). 2. Calcium plus vitamin D 3 (CD 3 ): as C plus 400 IU vitamin D 3 (10-mg cholecalciferol) (CaviD s chewable tablets, Nycomed, Denmark). 3. Placebo (P): tablets with identical appearance taste and content of vehicle (lactose, cellulose and sorbitol) as C and CD 3. The test dosage was two tablets daily taken: one with breakfast and one with the evening meal. The three 7-day study periods began with 4 days of normal diet (washout) followed by 3 days of test treatment. In order to avoid any carry-over effects of vitamin D 3 from CD 3 to the other periods, subjects started with either C or P according to randomization followed by CD 3. Neither investigator nor subject knew when C or P was given during the first 2 weeks (doubleblind) whereas only subjects were blind during the third week in which CD 3 was given (single-blind). Investigators controlled intake of test treatment, at the end of each week. Laboratory analyses Blood. Samples were drawn from a cubital vein at days 0, 8, 15 and 22. Serum was analyzed immediately for Ca 2 þ with a calcium-ion selective electrode (ICA II s, Radiometer A/S, Þ, creatinine and total alkaline phosphatase (ALP) with routine methods (Hitachi 917 s ). The following plasma analyses were done after the study and at the same time to minimize interassay coefficients of variation: Intact parathyroid hormone (1-84) (PTH) with a two-site RIA (Nichols Institute, CA, USA), 25 hydroxycholecalciferol and 1,25-dihydroxy-cholecalciferol (1,25(OH) 2 vit D) (days 0, 15 and 22) with RIA performed by a ISO 9000 certified commercial laboratory (Medilab, Copenhagen). Denmark) and for phosphate ðpo 3 4 Urine. Three consecutive 24-h collections of urine started after the subject had emptied the bladder in the morning of the 5th day of each period, that is, on the first test treatment day. After each 24-h collection period the urine was acidified and kept cold and handed over to the hospital laboratory for analysis by routine methods (Hitachi 917 s ) for each day separately. Only one urine sample of 144 ml was lost during the study. The study took place from early September to late November at Rigshospitalet, The Copenhagen University 1421

3 1422 Hospital, Denmark situated at latitude 55.61N. It was approved by the National Board of Health and the Ethics Committee of Copenhagen and performed according to the Declaration of Helsinki II version 1996 and ICH Good Clinical Practice (ICH-harmonised Tripartite Guidelines for Good Clinical Practice, 1996; World Medical Association Declaration of Helsinki 1964). Statistics The primary end point, that is, 24-h urinary calcium excretion, was tested with parametric analysis of variance (ANOVA). The hypothesis tested was whether the total amount of calcium excreted was equal for the three kinds of study medications. The 95% confidence interval for pairwise comparison of treatments was calculated by Scheffe s method for multiple comparisons. Additional laboratory variables served as secondary end points and were summarized using descriptive statistics. The significance level was set at 5%. All variables were inspected by means of QQ plots, histograms and Anderson Darling tests of the normal distribution assumption (using PROC CAP- ABILITY of SAS s System for Windows, Release 6.12). Results are presented as mean 7 s.d. and range. Since there are no significant differences between results for the intention to treat (ITT) population (n ¼ 17) and the per protocol (PP) population, that is, the number of subjects who completed the study and who were included in the efficacy analyses (n ¼ 16), PP data are presented here. Results The 24-h urinary calcium excretion increased by 35% ( mmol for C vs mmol for P) (Po0.05). The addition of 800 U of cholecalciferol during the 3 days (CD 3 ) did not increase the calcium excretion further (Table 1). The difference between group C and CD 3 was insignificant. The 24-h phosphate excretion was lower for group C ( mmol) compared to group P ( mmol) (Po0.05) but no difference between group CD 3 and group P and C was observed (Table 1). There was a 21% significant reduction in 1,25(OH) 2 vitamin D 3 from pmol/l at baseline to pmol/l at day 22 (Po0.05) whereas 25(OH)D 3 was unchanged in group CD 3 (Table 2). The concentrations of plasma Ca 2 þ, phosphate, PTH, creatinine and ALP did not change substantially during the three study periods (Table 2). Eight subjects reported a total of 10 adverse events that were all mild. Three subjects reported constipation, whereas the following events were reported by one subject: pain in the neck, migraine, diarrhoea, increased diuresis, palpitations, dry mouth and a tic bite. Compliance with intake of test treatment drugs (pill counting) and the study procedures was 100% (except for one lost urine sample). Discussion Calcium supplements are widely used by women at the menopause and thereafter to prevent osteoporosis. The benefits of calcium supplement to women early after menopause who are in a good nutritional status with respect to calcium and vitamin D are uncertain. During the first 2 3 y after menopause, the bone turnover is increased due to lack of oestrogen leading to increased excretion of calcium in the urine during this period. Calcium supplements are considered of limited value at least for the prevention of osteoporosis during this period. Table 1 24-h excretion of calcium, phosphate and creatinine in urine after oral supplement with 1000 mg calcium without (group C) or combined with 800 IU vitamin D3 per day (CD3) or placebo (P) for 3 days in 16 early postmenopausal healthy women on a calcium and vitamin D sufficient diet Group U-Ca (mmol) U-phosphate (mmol) U-creatinine (mmol) C (calcium only) 6.9* * CD 3 (calcium þ vitamin D 3 ) 6.6* P (placebo) * Po0.05 compared to placebo; (mean7s.d.). The values are the mean of three consecutive 24-h urine samples collected the last 3 days of each 1 week period. Table 2 Plasma concentrations of laboratory variables at baseline and after test treatments Day Ca 2 þ P PTH Creatinine ALP 25(OH)D 3 1,25(OH) 2 D 3 Baseline P, placebo 8/ NA NA C, calcium 15/ NA NA CD 3, calcium þ vitamin D *719 Reference interval Unit mmol/l mmol/l pmol/l mmol/l U/l nmol/l pmol/l * NA: not applicable; *Po0.05 compared to baseline; mean7s.d.

4 We did not measure bone markers but selected women who were at least four years after menopause to have as homogenous an early postmenopausal group of women with respect to calcium homeostasis as possible. However, other investigators have found no significant effects on markers of bone turnover of oral supplementation with 800 IU cholecalciferol daily for 2 years in postmenopausal women in a well-controlled twin-study in the UK (Hunter et al, 2000). Furthermore, vitamin D supplementation to early postmenopausal women had no significant positive effect on lumbar spine bone loss compared with placebo during a 5- y randomized trial in Finland (Komulainen et al, 1999). The calcium intake on average (1019 mg) in the present study subjects was close to that recommended at the time of screening for the study but showed a rather broad variation. After a slight dietary adjustment by the dietician the average calcium intake at start of study was quite homogenous around 862 mg and was kept constant during the study. The adjustment was done to minimize the risk of random and large variation in the calcium and phosphate excretion in the urine during the study. Under these circumstances and in vitamin D sufficient healthy subjects with a normal renal function we regard the 24-h calcium excretion as a fair estimate of the calcium absorption. Daily supplement of 1000 mg calcium carbonate increased the 24-h calcium excretion by 35%. The decrease in the phosphate excretion could indicate a transient suppression of the PTH-effect on the renal tubular reabsorption of phosphate. The plasma PTH concentrations were within the normal reference range and we did not see a substantial decrease in plasma PTH levels. This, however, could be due to the h period between last intake of calcium carbonate and the time for blood sampling next morning since the suppressive effect of an equivalent oral calcium load on plasma PTH concentration in short-term study occurs within 60 min (Tfelt-Hansen et al, 2001). We did not find a significant increase in calcium absorption by addition of 800 U cholecalciferol daily (group CD 3 ) compared with calcium carbonate alone which corroborates the results from another Danish study (Mortensen & Charles, 1996). Firstly, the majority of calcium absorption occurs in the duodenum through an active, regulated transport. Only a minor part occurs through a passive, paracellular pathway throughout the small intestine. The active calcium absorption is regulated by 1,25 (OH) 2 vit D 3 through its activating of intranuclear receptors followed by genomic upregulation of calbindin mrna expression and protein production in a matter of hours to days. In addition, 1,25 (OH) 2 vit D 3 also activates novel-specific membrane associated rapid response steroid binding proteins and thereby also excerts nongenomic effects within minutes (Kerstetter & O Brian, 2002). Contrary to the direct genomic and nongenomic effects of 1,25 (OH) 2 vit D 3, no such effects has been demonstrated for 25 (OH) 2 vit D 3. It is therefore unlikely that 800 U cholecalciferol daily as we used in the present study would increase the calcium absorption on short term. Secondly and more important, the study subjects were already in a good vitamin D nutritional status at the beginning of the study as judged by the normal serum concentrations of 25 (OH) 2 vit D 3, alkaline phosphatase, PTH and Ca 2 þ at baseline as well as unchanged plasma 25-hydroxyvitamin D 3 levels despite the supplementation. The study was performed from September to early November, that is, the season where we have the highest concentrations of plasma 25-hydroxyvitamin D 3 in Denmark. To avoid seasonal variations in vitamin D production, we concentrated the study to the early autumn to limit the number of confounding factors. It is therefore possible that the results would have been different if the study had been carried out during the winter or spring season since Copenhagen is located at 55.61N and the production of vitamin D precursors in the skin due to the UVB-radiation from the sun is almost absent from October to April above latitude 521N (Dawson et al, 1997). Another, hypothetical explanation of the lack of a clear effect of cholecalciferol is that variations in protein intake may have caused random variations in the calcium excretion and thus blur the results. A threefold increase in protein intake is reported to increase urinary calcium excretion and upregulate intestinal calcium absorption by around 50% (Farach-Carson & Nemere, 2003). In the present study, the subject were instructed to keep a normal diet with a relative constant calcium intake but no restrictions or guidance concerning the protein intake were given. This possibility, therefore, cannot be ruled out but according to our dietician none of the participants had excessive variation in the protein intake. Some effect of the vitamin D supplement did we, however, see, as the plasma calcitriol concentrations were 21% lower at the end of the CD 3 period, although within the normal reference range. Again this could be due to a transient suppression of PTH leading to a diminished 1-alpha vitamin D 3 hydroxylase activity in the kidney. The slightly lower phosphate excretion also supports this view but we did not follow the plasma PTH sufficiently frequent to support this firmly. From this well-controlled study, we conclude that supplementation with calcium and vitamin D in healthy women who are early after their menopause and who already eat an calcium and vitamin-d sufficient diet only have minor influences on the calcium metabolism. Acknowledgements We wish to thank the staff at the department of nephrology, especially Bente Spon, Betty Fisher and Kirsten Andersen for excellent help and support. References Aida K, Koishi S, Tawata M & Onaya T (1995): Molecular cloning of a putative Ca(2 þ )-sensing receptor cdna from human kidney. Biochem. Biophys. Res. Commun. 214,

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