Annals of Internal MedicineLong-Term Effect of Randomization to Calcium and Vitamin D Supplementation on Health in Older Women

Postintervention Follow-up of a Randomized Clinical Trial

A recent study published in the Women’s Health Initiative explores the long-term health effects of calcium and vitamin D supplementation in older women. This postintervention follow-up of a randomized clinical trial delves into the associations between these supplements and various health outcomes in postmenopausal women over two decades.

Study Design:

• Participants: 36,282 postmenopausal women across the United States, with no history of breast or colorectal cancer.
• Intervention: Participants were randomly assigned to receive either 1000 mg of calcium carbonate with 400 IU of vitamin D3 daily or a placebo.
• Duration: Follow-up after a 7-year randomized intervention trial, with a median cumulative follow-up of 22.3 years.
• Measurements: The study assessed the incidence of colorectal, invasive breast, and total cancer; disease-specific and all-cause mortality; total cardiovascular disease (CVD); and hip fracture.

Key Findings:

• Cancer Mortality: There was a 7% reduction in cancer mortality among participants assigned to calcium and vitamin D supplementation compared to the placebo group.
• CVD Mortality: A 6% increase in cardiovascular disease mortality was observed in the supplementation group.
• No Significant Impact: The study found no significant effect on all-cause mortality, cancer incidence, or hip fracture rates.
• Stratification Effects: Results varied when stratified by pre-randomization supplement use, especially concerning cancer incidence and CVD mortality.

According to the National Osteoporosis Foundation, approximately 10 million Americans have osteoporosis, and more than 44 million have low bone density, placing them at increased risk.

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