Calcium and Vitamin D Supplementation Plus Hormone Therapy Protects Bones

JULY 15, 2013
Aimee Simone, Assistant Editor
Supplementation with calcium and vitamin D led to significantly reduced risk of hip fracture when combined with postmenopausal hormone therapy, a recent study finds.

A number of recent studies have found an increased risk of heart problems associated with calcium supplements, and the US Preventive Services Task Force recently recommended against routine calcium and vitamin D supplementation for prevention of fractures in postmenopausal women. However, a study published online on June 24, 2013, in Menopause finds that for postmenopausal women taking hormone therapy, calcium and vitamin D supplements may reduce the risk of hip fractures.
To investigate conflicting results of previous studies on the effectiveness of both hormone therapy and calcium and vitamin D supplements in improving bone health and treating osteoporosis, the researchers evaluated the effects of these therapies on bone health when taken together and separately.
The double-blind study recruited postmenopausal women between the ages of 50 and 79 participating in the Women’s Health Initiative to enroll in an estrogen therapy clinical trial and an overlapping calcium and vitamin D trial between 1993 and 1998. A total of 27,347 women were randomly selected to receive hormone therapy or a placebo, while 36,282 women were randomly selected to take 1000 mg of elemental calcium and 400 IU of vitamin D3 daily or placebo. In all, 16,089 women participated in both the hormone therapy and calcium/vitamin D supplementation arms of the study. A subgroup of participants in the supplementation arm also reported their personal daily calcium and vitamin D intakes. Participants self-reported hip fractures semi-annually from the end of the trial through March 31, 2005. Fractures were confirmed by radiographic or operative reports.
After an average follow-up period of 7.2 years, the researchers found that there was a significant interaction between the effects of hormone therapy and supplementation. The effect of hormone therapy on fracture prevention was stronger among those receiving supplementation than among those receiving placebo, and the effect of supplementation was stronger among those receiving hormone therapy than among those receiving placebo. Overall, the results indicate that those receiving hormone therapy and supplementation would experience 11 hip fractures per 10,000 person-years, compared with 18 per 10,000 person-years for those receiving hormone therapy only, 25 per 10,000 years for those receiving supplementation only, and 22 per 10,000 person-years for those receiving placebo in both arms. (The difference in the latter 2 rates was not statistically significant.) 
The researchers conclude that supplementation with calcium and vitamin D may not prevent fractures on their own, but the supplements have a significant effect when combined with postmenopausal hormone therapy. Based on the data, the researchers could not specify the ideal calcium and vitamin D intake to achieve these results. However, based on data from the participants who reported their personal intake levels, they observed increased benefits with increased intake. The researchers conclude that more research is needed to determine whether the effect of other forms of osteoporosis therapy may be amplified when combined with calcium and vitamin D supplementation.

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