Calcium and vitamin D supplementation associated with lower risk of hip fracture among women receiving hormone replacement therapy
Friday, June 28, 2013. The results of a trial published online on June 26, 2013 in Menopause, the journal of The North American Menopause Society, add evidence to a bone-protective effect for supplementing with calcium and vitamin D among women receiving the hormone estrogen with or without progesterone. The findings are in conflict with a recently published US Preventive Services Task Force statement that there is insufficient evidence in favor of supplementing with the nutrients to lower fracture risk.
The trial included participants in the Women's Health Initiative, which recruited postmenopausal women between the ages of 50 and 79 years between 1993 and 1998. Among participants randomized to receive a placebo or hormone replacement therapy, 8,054 were assigned to receive 1,000 mg calcium and 400 mg vitamin D per day and 8,035 were assigned to a placebo.
Over an average of 7.2 years of follow-up, 214 hip fractures occurred. Women who received hormone therapy as well as calcium and vitamin D experienced a lower risk of hip fracture in comparison with those who received either treatment alone. Authors John A. Robbins, MD, MHS of the University of California Davis and his colleagues report that "The effect of hormone therapy on hip fracture prevention was stronger among women assigned to active calcium/vitamin D than among women assigned to placebo. Likewise, the effect of calcium/vitamin D was stronger among women assigned to active hormone therapy than among women assigned to placebo."
The combination of hormone therapy and calcium and vitamin D supplementation was determined to result in 11 hip fractures per 10,000 person-years in comparison with 22 fractures among those who received neither treatment. In subgroup analyses that included the subjects' personal calcium or vitamin D intake in addition to the amounts provided by the trial, the synergistic interaction of hormone therapy and these nutrients was consistent throughout all amounts of personal intake, and increased with higher intake levels.
"These results suggest that women taking postmenopausal estrogens should also take supplemental calcium/vitamin D," the authors write. "Because of the study design, we are unable to suggest a specific level of supplementation; benefit seems to increase with increasing total calcium/vitamin D intake."