Vitamin D Added to Calcium Helps Prevent Hip-Bone Loss in Older Women

By Judith Groch
PERTH, Australia, Jan. 18 -- The addition of vitamin D to high-dose calcium preserved hip-bone density over five years in women 79 to 80 years old living in a sunny climate, researchers here reported.
The five-year improvement with combined treatment was probably mediated by long-term reduction in bone turnover and reduction in parathyroid hormone levels, Richard L. Prince, M.D., of the University of Western Australia here, and colleagues reported online in a study to appear in the March issue of the Journal of Clinical Endocrinology & Metabolism.
At one year, hip bone density was preserved in women receiving calcium and in those receiving calcium plus vitamin D compared with placebo. However, by years three and five, only those given 1,000 IU of vitamin D (ergocalciferol) plus high-dose calcium maintained hip bone mineral density. This was especially so for those with low plasma 25OHD levels at baseline, the researchers reported.
The basis of suboptimal vitamin D levels is likely to be the result of reduced sun exposure and the reduced ability of the skin to synthesize vitamin D, causing older people to be at increased risk of inadequate vitamin D production in the skin, the researchers said.
So these data support the concept of supplementation of calcium and vitamin D in elderly women even in a sunny climate such as Perth, a latitude (32 degrees south) similar to that of San Diego in the Northern hemisphere.
Dr. Prince and colleagues recently reported that Vitamin D2 supplements (ergocalciferol) plus high levels of calcium appeared to reduce the risk of falls, especially during the winter months among high-risk older women in sunny Australia. (See: Vitamin D2 May Help Prevent Falls Among High-Risk Older Women)
The current long-term evaluation was nested within a larger study (Calcium Intake Fracture Outcome), a five-year double-blind, randomized, controlled calcium-supplementation study of 1,500 community-dwelling older women randomized to 1,200 mg calcium a day or placebo.
In this sub-study, the first 120 sequential patients (ages 70 to 80, mean 74.8 years) seen in September 1998 (end of winter in Western Australia) were randomized to 600 mg of calcium carbonate twice a day (1,200 mg) or a vitamin D placebo (the calcium group), similar calcium plus 1,000 IU of vitamin D as ergocalciferol once a day (calcium/vitamin D group), or double placebo.
Seventy-four participants (61.7%) had plasma vitamin D levels of less than 75 nmol/L at the outset. The average calcium intake at baseline was 1,010 mg/day, and 74.8% of participants had a calcium intake below 1,300 mg/day.
At one year, hip bone mineral density as measured by dual energy X-ray absorptiometry was preserved in the calcium/vitamin D group (-0.17%) and the calcium-alone group (0.19%) but not for the controls (-1.27%).
At year one, compared with controls, the calcium and calcium/vitamin D groups also had 6.8% and 11.3% lower plasma alkaline phosphatase, respectively (P≤0.02), and 28.7% and 34.5% lower urinary deoxypyridinoline concentration (DPD/Cr ratio), respectively (P≤0.05).
However, the benefit was maintained for only the calcium/vitamin D women at three and five years, and benefits were found mainly among those with baseline plasma 25OHD levels below the median (68 nmol/L), the researchers reported.
Compared with the control group at year three, hip bone mineral density was maintained for only the calcium/vitamin D women (calcium/vitamin D versus control, 2.8%, P=0.01) and at five years, 2.2% (P=0.05).
Thus, in the calcium/vitamin D group there was no bone loss over five years of the study, the researchers said.
Calcium/vitamin D also reduced plasma parathyroid hormone (PTH) concentrations at three and five years versus controls (27.8 and 31.3%, P≤0.005) in those with baseline parathyroid hormone levels above the median (3.6 pmol/L).
Therapy did not affect intestinal calcium absorption at high carrier loads.
There were no significant differences in adverse events among the three groups during the five-year study including the rate of incident cancer or vascular disease, and no kidney stones were reported.
Despite the findings about bone density in this study, Dr. Prince pointed out that a recent meta-analysis of clinical trials did not show increased efficacy for the combination of calcium and vitamin D compared with calcium alone on the important fracture prevention endpoint.
The mechanism of action of calcium plus vitamin D therapy is considered to be reducing bone turnover and suppressing plasma PTH in those with relatively high parathyroid hormone levels at baseline.
Among the study limitations was the fact that calcium absorption did not take into account losses of absorbed calcium to bone and urine. However, the higher concentrations of plasma calcium in both calcium groups compared with the control group at years one and three indicated that these two treatment groups had higher circulating levels as a result of supplementation.
Another limitation was that there was no vitamin D and calcium placebo group, so it was not possible to determine whether the effects on hip bone mineral density were due to vitamin D alone, or the interaction of the vitamin and calcium, the researchers wrote.
It should be noted, they added, that the study used ergocalciferol (vitamin D2) rather than the more potent cholecalciferol (vitamin D3), suggesting that the effect would be greater for cholecalciferol.
On the basis of these findings, the researchers concluded that even in sunny climates, the addition of vitamin D to high-dose calcium has long term beneficial effects on bone density and turnover in older women.
This study was supported by grants from the Healthway Health Promotion Foundation of Western Australia, the Australian Menopause Society, and the Australian National Health and Medical Research Council.
The authors had not financial disclosures to declare.
Additional source: Journal of Clinical Endocrinology & MetabolismSource reference: Zhu K, et al "Effects of calcium and vitamin D supplementation on hip bone mineral density and calcium-related analytes in elderly ambulatory Australian women: a 5-year randomized controlled trial" J Clin Endocrin Metab 2008: DOI: 10.1210/jc.2007-1466.