Calcium + Vitamin D = Reduced Cancer Risk?
August 9, 2007—Women who take calcium and vitamin D know they are doing something good for their bones; now new research suggests they are also preventing cancer.
The new study, published in the American Journal of Clinical Nutrition, looked at the effect of calcium alone and calcium plus vitamin D on cancer risk (excluding skin cancer) in healthy white women over the age of 55. The 1,180 women received either 1,500 mg of calcium in the form of calcium carbonate or 1,400 mg of calcium in the form of calcium citrate per day, the same amount of calcium plus 1,000 IU of vitamin D per day, or a placebo.
After four years, the women taking calcium were 47% less likely to have developed cancer than the placebo group. Cancer risk was even lower in the women taking calcium plus vitamin D: their risk was 60% reduced compared to placebo.
A second analysis excluded the women who developed cancer within the first year of the study, based on the assumption that these cancers may have been present but undetected at the beginning of the study. Calcium’s anticancer effect was virtually unchanged, but the effect of calcium plus vitamin D was enhanced: a 77% risk reduction was seen in the women using this combination.
When blood levels of vitamin D were considered, the women who had higher levels at the beginning of the study were protected against cancer regardless of group assignment, but women who had lower levels were not protected unless they were assigned to receive vitamin D.
A link between sunlight and cancer protection has been noted for more than 60 years and extends to cancers of the colon, breast, rectum, ovary, prostate, stomach, bladder, esophagus, kidney, lung, pancreas, and uterus as well as to non-Hodgkin lymphoma and multiple myeloma. The explanation, some believe, is due to vitamin D, which the body produces in response to sunlight.
More recently, researchers have found that people with even moderately low vitamin D levels in the blood have a higher risk of colon, prostate, and other cancers. A high calcium intake has also been shown to protect against some cancers, particularly colon cancer.
The new study is the first to look at calcium plus vitamin D supplements as an intervention to prevent cancer. “These findings give us yet another compelling reason to recommend calcium and vitamin D to postmenopausal women,” said Dr. Louise Tolzmann, a naturopathic doctor in Oregon specializing in cancer support. “And, it reminds us that the old recommendation of 400 IU of vitamin D per day is too low. The researchers’ use of 1,000 IU per day is likely to have been an important reason that their results were so impressive.” Up to 2,000 IU of vitamin D per day is generally considered to be safe for healthy adults.
(Am J Clin Nutr 2007;85:1586–91)
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Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, VT, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.
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