Older adults who took calcium were less likely to develop colon cancer than were those who did not take calcium, according to findings from two new studies.
Researchers from Dartmouth Hitchcock Medical Center in Lebanon, New Hampshire, recruited 930 older adults, average age 61, 72% of whom were men and 28% women, who had a recent history of pre-cancerous growths in the colon known as colorectal adenoma. Participants took 3,000 mg of calcium carbonate containing 1,200 mg of elemental calcium per day or a placebo for four years. Researchers gave each participant a colonoscopy exam to qualify for the study and repeated the exam after the first and fourth years. Doctors adjusted for risk factors including age, sex and lifetime number of adenomas, and found that, in 832 participants who completed the study, those who took calcium were 24% less likely to redevelop adenomas compared to placebo. The scientists noted that the level of dietary fats and calcium participants consumed prior to the study did not affect results.
In a second phase of the study, researchers continued to follow 822 participants for an average of seven years after the treatment/placebo period had ended, recording the medications, vitamins and supplements each participant took. Doctors reported that during the first five years after the study, those who had been in the calcium group were 37% less likely to develop any kind of adenoma compared to placebo, and that the calcium group was also 15% less likely to develop advanced (more serious) adenomas than placebo—a positive finding but one the researchers said was “not statistically significant.” The scientists noted that, in the five-year follow up period, the risk of developing adenomas in the calcium group was the same for those who continued to take calcium as for those who stopped taking calcium, and concluded that calcium protects against recurring colorectal adenomas up to five years after active treatment, even when participants stop taking calcium.