The risk for osteoporosis and related fractures rises after menopause . This rise is linked to the decline in naturally occurring estrogen that leads to bone weakening. Increasing calcium intake can improve bone density. However, it is not clear whether this increased bone density translates into fewer fractures; some studies support this effect, others do not. Findings from the Women’s Health Initiative (WHI) released earlier this year seemed to cast doubt on the efficacy of calcium supplements for bone protection. However, closer analysis of the WHI data showed that two subgroups of women—those older than 60 and those who took their calcium supplements at least 80% of the time—showed significant reductions in risk of hip fracture.

A recent study looked at how compliance with a calcium supplementation regimen affected fracture risk in women over age 70. The results, in the April 24, 2006 Archives of Internal Medicine, show that women who took calcium supplements at least 80% of the time had significant reductions in their risk of osteoporosis-related fractures.

About the Study

Australian researchers assigned 1,460 healthy women over age 70 to take either calcium supplements (600 milligrams [mg] each) or placebos twice daily for five years. Any unused pills were returned. Based on these unused pills, women were classified as compliant (took 80% or more of their assigned pills) or non-compliant (took less than 80%). Researchers compared bone density, osteoporosis-related fractures, and adverse events between the calcium and placebo groups, as well as the compliant and non-compliant subgroups.

After five years, there was no difference in fracture rates between the calcium and placebo groups. Significant changes were seen, though, among the 57% of women in the calcium group who took their supplements regularly. The compliant calcium-takers experienced greater improvements in bone density and fewer fractures compared with the compliant placebo-takers. These differences remained significant after adjustments were made for the effects of age, previous fractures, and body mass index (BMI) on bone health. Constipation was the only adverse event reported more often in the calcium group.

Vitamin D status is a possible limitation to this study. Although participants were “vitamin-D sufficient,” vitamin D levels could have been too low for complete calcium absorption, as there is controversy about the definition of “vitamin-D sufficient” as well as the best way to measure vitamin D status.

How Does This Affect You?

The message from this study is simple—in order to benefit from calcium supplements, you need to take them regularly. The researchers also conclude that 1,200 mg per day is a safe level of supplementation to lower the risk of osteoporosis-related fractures in women over age 70. This level may be too high for you, depending on your age, diet, and risk factors. Talk with your doctor to decide if a supplement is right for you, as well as which one and how much to take.

Calcium is one lifestyle factor that can improve bone health. Take the following steps to protect your bones:

  • Eat a balanced diet rich in calcium, vitamin D, and fruits and vegetables (produce provides potassium and vitamin K, which are linked to bone health)
  • Exercise for 30-60 minutes per day; include weight-bearing exercise, such as walking, running, and weight/resistance training (swimming is not weight-bearing) to strengthen bones
  • Don’t smoke
  • Don't drink excessively
  • Have your bone density tested at age 65, or earlier when appropriate