A Report from the Women's Health Initiative -- Calcium, Vitamin D and Fracture Risk
February 28, 2006 -- Calcium and Vitamin D Report - Risk of Fracture
A recent study from the New England Journal of Medicine was released in the February 16th, 2006 edition that reported on results regarding Calcium and Vitamin D supplementation and risk of fractures. This study was a part of the Women's Health Initiative and randomly assigned over 36,000 women to receive 1000 milligrams of calcium carbonate and 400 international units of vitamin D or placebo. These women were then followed over 7 years regarding fractures and bone density. The conclusions drawn from the study revealed a small but significant improvement in hip bone density, no significant reduction in hip fracture and an increased risk of kidney stones. This trial was well conducted but left many questions unanswered.
While the general conclusions are important to note, a few important points are worthwhile to keep in mind:
* Women in the calcium/vitamin D group had a 1% significant higher hip bone mineral density than women in the placebo group. A higher bone density is associated with a lower risk of fracture. The rate of hip fracture in this study was lower than planned for and may be the reason that no significant reduction of hip fracture occurred. This could be due to the fact that over half of the participants were also receiving hormone replacement therapy, which significantly reduces the risk of fracture.
* When breaking down the sub-groups of study participants, the women at greatest risk of hip fracture who were enrolled in the calcium/vitamin D group had a clinically significant benefit. Women who were adherent to their study regimen (those who took over 80% of their study calcium/vitamin D) had a significant 29% reduction in hip fracture. Women aged 60 and over (those at highest risk of fracture) had a significant 21% reduction in hip fracture risk.
* Sixty four percent of women in the placebo group had a daily calcium intake from diet and supplements of at least 800 milligrams and 42% had a daily vitamin D intake of at least 400 international units. Also, the women in the study had average daily calcium intake of 1150 milligrams before the study began, which is nearly double the national average. This intake may certainly reduce the chances of detecting a benefit of calcium and vitamin therapy in this study.
* The study did not reveal any difference between the calcium/vitamin D group and placebo group in the rate of adverse GI events, such as gas, bloating, or constipation.
* The small increase in kidney stone formation is contrary to a number of prior studies that showed no increased risk or a decreased risk of kidney stone formation.
Therefore, this study is another important piece in the context of significant data that exists revealing the benefits of calcium and vitamin D to bone health. It is well known that optimal bone mass and health occurs between 20 and 30 years of age. As the perimenopause and menopause occurs, significant bone loss can occur. Hence, it is important to remember that calcium/vitamin D should serve as a foundation for bone health throughout life.
This study should raise awareness for a few key points:
1) Even if adequate calcium/vitamin D is obtained through diet or supplements, a woman should be aware that she still may be at risk for osteoporosis and/or fracture.
2) Woman taking medications for osteoporosis (such as Boniva, Fosamax, Actonel, Evista and others) should remember that these medications work most effectively when an adequate amount of calcium and vitamin D is present.
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