Calcium May Only Protect Against Colorectal Cancer in Presence of Magnesium
November 16, 2008
WASHINGTON, D.C. - According to data presented at the American Association for Cancer Research's Seventh Annual International Conference on Frontiers in Cancer Prevention Research, an understanding of the relationship between calcium and magnesium may lead to new avenues of personalized prevention for colorectal cancer.
High magnesium intake has been associated with low risk of colorectal cancer. Americans have similar average magnesium intake as East Asian populations. If that were all that were involved, observers might expect both groups to have similar risk for colorectal cancer.
However, the United States has seen a much higher colorectal cancer incidence rate than East Asian populations. Furthermore, when East Asians immigrated to the United States, their incidence rates for colorectal cancer increased. This led researchers at Vanderbilt University to suspect there was something else at work.
Calcium supplementation has been shown to inhibit colorectal carcinogenesis although high calcium may simultaneously be preventing the body from absorbing magnesium. United States patients have a higher calcium intake and higher colorectal cancer incidence. "If calcium levels were involved alone, you'd expect the opposite direction. There may be something about these two factors combined - the ratio of one to the other - that might be at play", said Qi Dai, M.D., Ph.D., assistant professor of medicine at Vanderbilt University.
Dai and colleagues examined this hypothesis in a large clinical trial and found indeed that supplementation of calcium only reduced the risk of adenoma recurrence if the ratio of calcium to magnesium was low and remained low during treatment. "The risk of colorectal cancer adenoma recurrence was reduced by 32 percent among those with baseline calcium to magnesium ratio below the median in comparison to no reduction for those above the median," said Qi.
The implications for prevention of adenoma recurrence or reduced risk of primary colorectal cancer is that designing a personalized diet/supplementation regimen that takes the ratio of both nutrients into account may be better than supplementing with one or the other alone.
About one in eighteen individuals will develop colorectal cancer in their lifetime and 40 percent will die within five years of diagnosis, mainly due to diagnosis at a late stage. The understanding of how dietary factors affect colorectal cancer may lead to the prevention of cancer recurrence and possibly prevention of the initial cancer.
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The mission of the American Association for Cancer Research is to prevent and cure cancer. Founded in 1907, AACR is the world's oldest and largest professional organization dedicated to advancing cancer research. The membership includes more than 28,000 basic, translational and clinical researchers; health care professionals; and cancer survivors and advocates in the United States and 80 other countries. The AACR marshals the full spectrum of expertise from the cancer community to accelerate progress in the prevention, diagnosis and treatment of cancer through high-quality scientific and educational programs. It funds innovative, meritorious research grants. The AACR Annual Meeting attracts more than 17,000 participants who share the latest discoveries and developments in the field. Special conferences throughout the year present novel data across a wide variety of topics in cancer research, treatment and patient care. The AACR publishes five major peer-reviewed journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention. The AACR's most recent publication and its sixth major journal, Cancer Prevention Research, is dedicated exclusively to cancer prevention, from preclinical research to clinical trials. The AACR also publishes CR, a magazine for cancer survivors and their families, patient advocates, physicians and scientists. CR provides a forum for sharing essential, evidence-based information and perspectives on progress in cancer research, survivorship and advocacy.
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