June 24, 2004
by Jenny Thompson
Health Sciences Institute

In the most recent issue of the Journal of the National Cancer Institute, researchers from the Dartmouth-Hitchcock Medical Center in Lebanon, NH, published an analysis of data collected from 930 patients enrolled in the Calcium Polyp Prevention Study.

All of the study subjects had been diagnosed with colorectal polyps. Divided into two groups, participants received either a 1,200 mg daily supplement of calcium carbonate, or a placebo. Two colonoscopies were conducted approximately one year and four years after each subject's initial exams.

The researchers found that while calcium supplements may provide some protection against the development of polyps, the supplements proved most effective against advanced polyps. Subjects who received calcium supplements had generally fewer polyps compared to the placebo group. But as the lead author of the study, Dr. John A. Baron told Health Day News, calcium may help lower the risk of advanced polyps by as much as 45 percent.

The subjects who experienced the greatest benefits were those who also had high intakes of calcium in their diets, as well as high fiber and low fat intakes (although these other dietary interactions were described as "not statistically significant").

According to Dr. Baron, this study expands on what we already know about calcium's ability to prevent polyps with the encouraging news that calcium seems to also offer protection against polyps developing into cancer.

A note on calcium

As the Dartmouth-Hitchcock study suggests, one obvious way to support the effectiveness of calcium supplements is to make sure you include plenty of calcium-rich foods in your diet, such as salmon, cabbage, kale, and yellow, green, or waxed beans.

As I mentioned above, the type of supplement used in the study was calcium carbonate. And as HSI Panelist Allan Spreen, M.D., told us in the e-Alert "Absorbing it All" (4/19/04), calcium carbonate is the most common, most readily available and least expensive type of calcium supplement. But the carbonate form does have two drawbacks: It's not as well absorbed as some other inorganic forms of calcium, and it binds the most acid.

The latter problem presents both a potential plus, as well as a minus. Some scientists believe that calcium's ability to bind acids may be the very reason it protects against cancer. But binding digestive acids may also result in poor absorption of nutrients and indigestion. So if a 1,200 mg supplement of calcium is taken daily, along with good sources of calcium in the diet, keep an eye out for digestive problems that may be managed by adjusting the dosage of the supplement.

In addition, Dr. Spreen notes that, "Calcium is not found in nature (in edible form) without magnesium, and they therefore should always be given together."

Foods that are high in magnesium include leafy green vegetables, whole grains, bananas, apricots, meat, beans, and nuts.

Added prevention -------------------------------------------------

A 2002 study published in Cancer Epidemiology, Biomarkers, and Prevention showed that those with a family history of colon cancer may cut their risk by as much as 50 percent with a supplement of 400 micrograms of folate daily. In addition to supplements, spinach and asparagus provide good sources of folate.

And if you do decide to supplement with folate and calcium, consider taking one more important preventive step: Ask your doctor about arranging for a colonoscopy, which is recommended every three to five years for everyone over the age of 50; especially those with a family history of colon cancer.