Calcium + Vitamin D Supplements = A Mixed Bag

Colorectal cancer and hip fractures not reduced with calcium and vitamin D supplements

/ Author:  / Reviewed by: Beth Bolt, RPh

(RxWiki News) Keeping track of which dietary supplements are beneficial, harmful, or do nothing at all is a time-consuming endeavor. So what’s the latest information on calcium and vitamin D supplements?

A follow-up study of the Women’s Health Initiative (WHI) Calcium plus Vitamin D Supplementation Trial is now suggesting that calcium and vitamin D supplements do not reduce a postmenopausal woman’s risk of colorectal cancer or hip fractures.

Results immediately following the original seven-year trial were somewhat different.

However, these supplements were found to lower the risks of ductal carcinoma in situ (DCIS), the earliest form of breast cancer, and reduce the risk of vertebral (bones around the spine) fractures.

The supplements had no significant effect on cardiovascular disease, overall cancer incidence, or death.

"Talk to your physician before taking any dietary supplement."

Jane Cauley, DrPH, a researcher at the University of Pittsburgh, and colleagues conducted a follow-up of WHI Calcium plus Vitamin D Supplementation Trial five years after it was completed.

The original study involved 36,282 women between the ages of 50 and 79 who were randomly assigned to take 1,000 mg of calcium carbonate with 400 IU of vitamin D3 or a placebo (sugar pill).

At the end of the seven-year trial, these researchers found a 29 percent reduced risk of hip fracture among women who took the supplements compared to women in the placebo group.

Investigators also determined there were no significant differences between the groups in the incidence of colorectal cancer, in situ or invasive breast cancer, cardiovascular disease (CVD), overall cancer incidence, or all-cause mortality (death from any cause).

The current study assessed the effects of supplementation on hip fracture and colorectal cancer among 29,862 women nearly five (4.9) years after the original study ended.

Here’s what the follow-up study discovered:

  • Hip fracture rates were similar between the two groups.
  • Vertebral fractures were 17 percent lower in the supplement group compared to the untreated group.
  • There was indication of increased invasive breast cancer incidence among women whose vitamin D intake was higher at the start of the trial.
  • The risk of in situ breast cancer that has not invaded tissue beyond the original site was 18 percent lower among women of all ages who took the supplements than among the women who took the placebos.
  • The risk of vertebral fractures was 20 percent lower in women over the age of 60 who took the supplements.
  • Women in the supplement group who were not taking calcium supplements before enrolling in the study had a 9 percent lower risk of developing any kind of cancer.

dailyRx News spoke with Deborah Gordon, MD, nutrition and preventive medicine expert and integrative physician at Madrona Homeopathy in Ashland, Oregon, about this study.

She pointed out that more has been learned about vitamin D and calcium supplementation since the original study began.

“D supplementation will increase calcium absorption, and we all want calcium in our bones, not tendons or arteries, which is the work of vitamin K2. Additionally, we know that vitamin D's immune function involves two other fat-soluble vitamins (A and again, K2) which are often deficient in the standard American diet,” Dr. Gordon explained.

“I caution people that vitamin adequacy is best achieved through a wide variety of nutrient-dense foods (including the egg yolks and butter that are often shunned), and that vitamin supplementation is best managed by a consultation with an MD, ND [naturopathic doctor], or nutritionist well-versed in all vitamins and their interactions."

Dr. Gordon, who was not involved in this study, added, “I always add fermented cod liver oil (sources of D, A, and K2) to a vitamin D recommendation.”

This follow-up study was published in the November issue of The Oncologist.

The research for this study was supported by the National Heart, Lung, and Blood Institute and the General Clinical Research Center program of the National Center for Research Resources, Department of Health and Human Services. Glaxo SmithKline Consumer Healthcare provided the supplements.

No conflicts of interest were disclosed.

Reviewed by: 
Review Date: 
November 21, 2013
Last Updated:
December 30, 2013