A recent study examined how common supplements, specifically calcium and vitamin D, are linked to mortality risk from heart disease and cancer. The findings revealed that women taking these supplements had a reduced risk of dying from cancer but a slightly increased risk of dying from heart disease if they were postmenopausal.

The Women’s Health Initiative (WHI) previously studied the health effects of daily calcium and vitamin D supplementation in postmenopausal women and found no significant impact. However, new research published in the Annals of Internal Medicine re-evaluated follow-up death data to assess the long-term health effects of these supplements.

In the U.S., older women often have diets deficient in vitamin D and calcium, leading many doctors to recommend supplements. This study highlights the complex relationship between supplements and health outcomes and emphasizes the need for further research, according to Dr. Cheng-Han Chen, a board-certified interventional cardiologist not involved in the study.

The research evaluated health data from the WHI trial and the National Death Index to determine the impact of long-term daily calcium and vitamin D supplementation on women's risk of cancer or heart disease. Women who took the supplements had a 7% lower risk of dying from cancer over 22 years compared to those on a placebo. However, they faced a 6% higher risk of dying from cardiovascular disease, especially if they had been taking supplements before the trial.

Supplementation did not significantly affect the overall prevalence of cancer, heart disease, hip fractures, or all-cause mortality. Dr. Chen noted that the study found a long-term association between calcium and vitamin D supplementation in postmenopausal women with decreased cancer mortality and increased cardiovascular disease mortality.

The mechanisms behind these effects are not entirely clear. Some research suggests that calcium and vitamin D supplements may decrease tumor invasiveness, impede angiogenesis (formation of new blood vessels around tumors), and influence gut functions and bile acid production. Vitamin D, in particular, has been shown to suppress tumor genes and regulate inflammation, potentially decreasing cancer cell growth and increasing cell death, according to Dr. Fredrick Schumacher, who was also not involved in the study. A recent meta-analysis linked vitamin D supplementation to a 13% reduction in cancer mortality.

The link between calcium and vitamin D supplementation and heart disease is more controversial. Excess calcium may lead to coronary artery calcification, increasing the risk of heart disease. Past research has identified a higher risk of coronary heart disease with calcium supplementation, irrespective of vitamin D intake. Michelle Routhenstein, a preventive cardiology dietitian, explained that coronary artery calcification can lead to heart disease, heart attacks, and strokes.

Despite these findings, calcium and vitamin D supplementation is often recommended for those with inadequate dietary intake and postmenopausal women to prevent osteoporosis and fractures. However, the optimal dosages and regimens remain debated among doctors due to concerns about long-term health effects. Routhenstein emphasized the importance of assessing current calcium intake before supplementing to avoid excessive intake, which could contribute to coronary artery calcium progression.

More research is needed to determine the ideal duration and dosage of these supplements. Dr. Schumacher highlighted that while the study provides important insights, these findings need to be replicated and evaluated in more diverse populations.

Conclusion:

Calcium and vitamin D supplements may reduce cancer mortality risk but could slightly increase heart disease mortality risk in postmenopausal women. Given the dietary deficiencies in older women, doctors often recommend these supplements. However, this study underscores the need for more research to understand the long-term health effects of daily supplementation.