Written by Marcia J. Egles, MD. Research in a group of 930 people showed 1.9% had minor fractures in the placebo group compared to 0% in the calcium supplementation group.

Medical literature includes conflicting data and opinions concerning the role of calcium supplements, with or without vitamin D, and bone health and the prevention of osteoporosis (1). In a recent clinical trial, a clear benefit in reducing bone fracture risk was found for a group of healthy Americans treated with 1200 mg per day of calcium supplements for four years. The trial is a follow-up study of the Calcium Polyp Prevention Study (2) which began in 1988 in six U.S. locations, ranging from Minnesota to sunny southern California.

The Calcium Polyp Prevention Study involved 1,118 men and women, aged 27 to 79, (average age 61), who recently had a benign polyp* removed by colonoscopy. They were randomly assigned to swallow either a placebo tablet or 3 grams of calcium carbonate (1200 mg elemental calcium) daily over four years.  No vitamin D was supplemented and no additional supplements with calcium were allowed. The calcium dietary intake of the placebo group averaged 865 milligrams per day and that of the calcium group was 889 milligrams per day.  The average vitamin D levels in the blood of both groups were slightly low (but nearly normal). Over 83% of the participants reported taking at least 80% of the tablets for the four years.

The original trial reported a moderate reduction in bowel polyps on repeat colonoscopy in the calcium group, compared to the placebo group. The participants were informed of the results of the study, but not which group they were in. Whereas only 2% of the subjects had used calcium supplements prior to the trial, 26% reported taking them for at least half of the follow-up years.

The new study looked at the frequency of bone fractures in the two groups, both during the four-year calcium treatment trial, and until the end of the study in 2003. Nine hundred and thirty participants, 72% male, were recruited for the extended study. Bone fracture events were reported through telephone interviews. The reported fractures were classified and confirmed by medical record review performed by two independent physicians. The bone fractures were classified as with either “minimal” or “significant’ trauma. Trauma was defined as minimal if the fracture occurred after falling from standing height or lower while sitting, standing or walking. Examples of significant trauma would include sports injuries, car crashes, or falling down stairs.

During the original four-year treatment phase, there were no minimal trauma fractures at all in the calcium treatment group. Nine such fractures occurred in the placebo group. After the end of calcium treatment, minimal trauma fractures were reported at statistically similar rates of frequency between the two groups. The rates of significant trauma fractures were found to be similar between both groups in the treatment and in the follow-up phase of the study.

This clinical trial is important because it shows a beneficial reduction in bone fractures occurring with low-level impacts among generally healthy adults who took 1200 milligrams daily calcium supplements. Adding in the baseline dietary intake, the calcium intake of the Americans treated in this trial was around 2100 milligrams per day.

The United States National Institute of Health and other experts recommend that, in general, adults should consume 1,200 milligrams of calcium each day. They also endorse that up to 2,000 – 2,500 milligrams a day of calcium from dietary sources and supplements appears to be safe. (3)

Source: Bischoff-Ferrari, Heike A., Judy R. Rees, Maria V. Grau, Elizabeth Barry, Jiang Gui, and John A. Baron. “Effect of calcium supplementation on fracture risk: a double-blind randomized controlled trial.” The American journal of clinical nutrition 87, no. 6 (2008): 1945-1951.

© 2008 American Society for Nutrition

Posted August 27, 2008.

References:

  1. Bischoff-Ferrari HA, Dawson-Hughes B, Baron JA, et al. Calcium intake and hip fracture risk in men and women: a meta-analysis of prospective cohort studies and randomized controlled trials. Am J Clin Nutr 2007;86:1579–80.
  2. Baron JA, Beach M, Mandel JS, et al.  Calcium supplements for the prevention of colorectal adenomas. Calcium Polyp Prevention Study Group. N Engl J Med 1999;340 (2) 101-107.
  3. Calcium Recommendations: posted on the Medline Plus website.

* A colon polyp, also known as an adenoma, is a fleshy growth that can occur on the inside lining of the intestine.  They are generally harmless, but sometimes can develop into cancers.