20 year study of vitamin D and calcium: less cancer but more heart disease

Should you take long term vitamin D and calcium or not?

A new study has some scratching their heads over whether vitamin D and calcium supplements could lower our risk of dying from cancer while simultaneously increasing our risk of dying from heart disease. 

The study, published in Annals of Internal Medicine, is a unique long-term follow-up study of a clinical trial run in the 1990s. 

The original trial was part of the Women’s Health Initiative (WHI) Study, which looked at the effects of calcium and vitamin D supplementation, HRT and dietary modification in postmenopausal women aged 50–79.

What happened in the initial study? 

Trial participants – around 50,000 – received either 1,000 mg calcium plus 400 IU vitamin D3 daily for 7 years or a placebo. What’s important to know is that the trial included some women who were already taking supplements before the trial started. 

When the researchers designed the trial, they wanted to know if supplementation would reduce fractures, particularly hip fractures, as well as colorectal cancer. 

Photo by Roberto Sorin

Initially, the results reported no significant reduction in hip fractures, a potential increased risk of kidney stones and a small improvement in hip bone density. 

A further analysis several years later claimed that 

a subset of women who hadn’t taken either of the supplements before the trial might have a lower risk of hip fractures at the end of the study. 

But before you rush out to stock up on supplements, I’ll also mention an even better   separate clinical trial of 25,000 women published in 2022 in The New England Journal of Medicine that showed no benefits whatsoever on fracture risk in women aged 55 and over.