Greater intake of calcium, vitamins associated with lower colorectal cancer risk
Tuesday, February 14, 2012. The February, 2012 issue of the journal Anticancer Research reports a lower risk for colorectal cancer in association with increased intake of calcium, vitamin C, vitamin D, vitamin B2 (riboflavin) and folate.
Scientists from Canada and China matched 1,760 Canadian men and women with colorectal cancer with 2,481 control subjects. Dietary questionnaire responses were used to quantify the intake of calcium, iron, folate and vitamins A, B1, B2, B6, B12, C, D and E from food and supplements.
The team observed diminishing odds of having colorectal cancer in association with increased intake of calcium, vitamin C, vitamin D, riboflavin and folate from dietary and supplemental sources. Those whose intake of calcium from supplements and food was among the top one-fifth of participants had a 41 percent lower adjusted risk of colorectal cancer compared to those whose intake was among the lowest fifth, and for riboflavin, the risk was 39 percent lower for subjects in the highest fifth. Having a greater intake of iron from food and supplements was associated with an increased risk of the disease, in regard to which the authors note that the mineral generates free radicals that attack DNA and damage chromosomes, which contributes to the risk of cancer.
A reduction in risk was also observed for increased consumption of these nutrients when derived from food alone, although the decrease was not as great as that observed for food plus supplemental sources. "We observed that inverse associations of calcium, vitamin C, folate and colorectal cancer were mostly pronounced among users of individual supplements," Zhyoyo Sun and colleagues write. "One possibility is that the intake of micronutrients from supplemental sources additionally contributes to the differences between cases and controls, and adds to the total amount of micronutrient intake, making the protective effects more likely to be detected. Thus, we presume that using individual supplements that provide compensatory micronutrients may reduce risk for colorectal cancer."
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In the January, 2012 issue of the Canadian Journal of Physiology and Pharmacology, researchers from King Saud University in Riyadh, Saudi Arabia reveal the finding of a protective effect for vitamins and minerals against colon cancer in rats.
Two-thirds of a group of sixty male rats were injected with the colon-specific carcinogen DMH weekly for 15 weeks. Animals that did not receive DMH were subdivided to receive a regular diet or a diet enhanced with vitamins and minerals. While one group of carcinogen-treated animals received no supplementation, the remainder received supplemented diets during the 15 weeks DMH was administered, for 16 weeks after the carcinogen was administered, or throughout the 32-week treatment period. Lipid peroxidation products and antioxidant enzyme levels were measured in blood and tissue at the end of the experiment, and the animals were examined for aberrant crypt foci, a precursor of colorectal adenoma.
Rats that received DMH had higher levels of lipid peroxidation and lower antioxidant status in comparison with animals that did not receive the carcinogen; however, vitamin and mineral supplementation reversed these trends. Supplemented animals experienced a significant reduction in aberrant crypt foci compared to carcinogen-treated rats that received unsupplemented diets.
The authors conclude that "multivitamin and mineral supplements synergistically contribute to the cancer chemopreventative potential, and hence, regular supplements of multivitamins and minerals could reduce the risk of colon cancer."
"It has been unclear whether multivitamin supplementation to cancer patients is helpful, has no effect, or is even detrimental during therapy," remarked Canadian Journal of Physiology and Pharmacology editor Dr Grant Pierce. "This study is important because it gives some direction to cancer patients in desperate need of guidance on the value of multivitamins and minerals administered during cancer."
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