Calcium May Improve Bone Mineral Density in Men
Calcium supplements at 1200 mg/day are beneficial for treating bone mineral density (BMD) in men to an extent comparable vs that seen in women, but a dosage of 600 mg/day is ineffective, according to the results of a double-blind, randomized controlled trial reported in the November 10 issue of the Archives of Internal Medicine.
“There is no consistent evidence, to our knowledge, that calcium supplementation affects…BMD in men, despite male osteoporosis being a common clinical problem,” write Ian R. Reid, MD, from University of Auckland in Auckland, New Zealand, and colleagues. “It is critically important to determine whether the widespread use of calcium supplements in older men is a worthwhile investment because 30% of older men experience a fragility fracture and men account for one-quarter of all hip fractures.”
For a 2-year period at an academic clinical research center, 323 healthy men 40 years or older (mean age, 57 years) were recruited by newspaper advertisement and randomly assigned to receive daily supplementation with calcium 600 mg/day, calcium 1200 mg/day, or placebo. Follow-up was complete in 96% of subjects.
In the group receiving calcium at 1200 mg/day, BMD increased at all sites by 1% to 1.5% more vs those receiving placebo, but BMD in the group receiving calcium at 600 mg/day did not differ from the placebo group at any BMD site. No interaction was demonstrated between the BMD treatment effect and either age or dietary calcium intake.
In men receiving calcium at 1200 mg/day, there were dosage-related, sustained decreases at 2 years in serum parathyroid hormone levels (25% decrease; P < .001), total alkaline phosphatase activity (8% decrease; P = .01), and procollagen type 1 N-terminal propeptide levels (20% decrease; P < .001).
Calcium supplementation did not appear to affect tooth loss, constipation, or cramps. Although falls occurred less often in the group receiving calcium at 1200 mg/day, both calcium-supplemented groups tended to have more vascular events vs the placebo group.
Limitations of this study include single-center study in a predominantly white cohort of vitamin D–sufficient men, use of calcium citrate, and insufficient statistical power for many other end points.
"Calcium, 1200 mg/d, has effects on BMD in men comparable with those found in postmenopausal women but a dosage of 600 mg/d is ineffective for treating BMD," the study authors write. "These findings provide a rationale for conducting randomized studies of the effect of calcium supplementation on fracture incidence in men. Such studies should also assess the incidence of cardiovascular events so that the balance of risk and benefit can be clearly determined."
Clinical Context
Calcium supplementation is essential to the prevention of osteoporosis in postmenopausal women, but less is known about the efficacy of calcium supplementation on fractures and BMD in men. There are 30% of older men who experience fragility fractures, with men accounting for one quarter of all hip fractures.
This is a double-blind, randomized, placebo-controlled trial to examine and compare the effects of 2 doses of calcium supplementation on BMD, fractures, falls, and adverse events in men without calcium insufficiency.
Study Highlights
* Included were healthy men 40 years and older recruited by newspaper advertisement.
* Excluded were men with any major illness, estimated cardiovascular risk of more than 15% for 5 years, renal dysfunction, or use of hormones.
* After a 1 month run-in, only those with at least 70% adherence to medication were accepted.
* Men were randomly assigned to receive 1 placebo tablet twice daily (n = 107), one 600-mg/day calcium citrate tablet for the 600-mg/day group (n = 108), or two 600-mg/day calcium citrate tablets for the 1200-mg/day group (n = 108) for 2 years.
* BMD was measured at 6-month intervals in the lumbar spine, the proximal part of both femora, and total body with use of a Prodigy dual-energy x-ray absorptiometer (GE-Lunar, Madison, Wisconsin).
* Vertebral morphometry was performed at baseline and at 2 years.
* Subjects were asked about fractures and kept a diary of their falls.
* Follow-up visits occurred every 6 months.
* Grip strength was measured in the dominant hand.
* Dietary calcium intake was assessed with a food frequency diary.
* Serum-25 hydroxyvitamin D level was measured as were levels of bone turnover markers.
* Mean age of participants was 56 years, 1% to 6% were current smokers, mean weight was 83 kg, and mean body mass index was 26 kg/m2.
* Complete follow-up was achieved in 96% of subjects: 93% for placebo, 91% for the low-dose calcium group, and 86% for the high-dose calcium group.
* Medication compliance was 85% for the placebo group, 86% for the low-dose calcium group, and 83% for the high-dose calcium group.
* The 600-mg/day group showed no difference from the placebo group for BMD at 2 years.
* The 1200-mg/day group showed a significant increase in BMD of 1% at 1 year; this difference was maintained to the end of the study.
* For total hip BMD, there was no difference between the 600-mg/day group and the placebo group, and the 1200-mg/day group showed a significant increase of 0.9% in year 1 with an additional 0.5% improvement in year 2.
* The hip changes showed improvement with time.
* The improvements in BMD for the 1200-mg/day group were not dependent on dietary calcium intake.
* Total body scans showed a similar pattern to the lumbar spine for the 1200-mg/day group, with an increase of 1.2% in the first 6 months and a more gradual increase to 1.5% above baseline by the end of the study.
* Falls decreased significantly in the 1200-mg/day group, but not in the 600-mg/day group, vs placebo (fall rates of 45, 65, and 59, respectively, per 100 person-years).
* Fasting levels of parathyroid hormone showed a dose-related decrease in the 2 supplemented groups.
* Bone turnover measured by markers showed dose-related sustained changes in response to calcium.
* There were no significant differences in fracture rates among the 3 groups and no differences in height loss.
* Adverse events including constipation, tooth loss, and cramps were similar among the 3 groups.
* Grip strength was similar in the 3 groups.
Pearls for Practice
* Calcium supplementation with 1200 mg/day, but not 600 mg/day, for 2 years vs placebo is associated with an increase in BMD in men with adequate dietary calcium intake.
* Calcium supplementation for 2 years with 1200 mg/day is associated with a reduction in falls, but not fractures, in men with adequate dietary calcium intake, and adverse events are not increased.
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