To date, scientific studies on the effects of calcium intake on colon cancer risk have yielded mixed results. A new study published in the recent issue of the
Journal of the National Cancer Institute
suggests that moderate increases in calcium intake may indeed reduce your risk of colon cancer.
About the study
Researchers from Harvard's Medical School and School of Public Health studied 87,998 women in the Nurses' Health Study (NHS) and 47,344 men in the Health Professionals Follow-up Study (HPFS). The NHS was conducted from 1980 through May 1996 and the HPFS was conducted from 1986 through January 1996.
In both studies, participants completed mailed questionnaires about medical history and dietary and lifestyle habits. NHS participants completed dietary questionnaires in 1980, 1984, 1986, 1990, and 1994. HPFS participants completed dietary questionnaires in 1986, 1990, and 1994. Participants in both studies were followed up until 1996. People with ulcerative colitis or previous cancer, other than nonmelanoma skin cancer, were excluded from this study.
The dietary questionnaires asked participants to estimate how often they ate various foods, beverages, and supplements containing calcium. Researchers compared the rate of colon cancer among people with higher calcium intakes with the rate among people with lower calcium intakes.
People who consumed 700-800 mg of calcium per day were 40% to 50% less likely to develop cancer in the lower part of the colon (distal colon) than their counterparts who consumed 500 mg or less per day. However, higher calcium intake was not associated with a decrease in cancers of the upper part of the colon (proximal colon).
In addition, the reduced risk of distal colon cancer seemed to be restricted to people with higher calcium intake
higher vitamin D intake. Vitamin D is known to help the body absorb calcium. The data also suggest that this reduced risk may be further restricted to people who didn't take aspirin. Researchers also found that calcium supplements reduced the risk of colon cancer in people with low calcium intake from food, but did not provide any benefit for people with higher dietary calcium consumption. This suggests there is a limit to the amount the calcium a person needs to eat to protect against colon cancer.
In calculating the risk of colon cancer, the researchers accounted for other factors that could affect colon cancer risk, such as age, exercise, body mass index, family history of colon cancer, smoking, and alcohol consumption.
There are limitations to this study, however. Both studies relied on participants to estimate their average consumption of foods and supplements containing calcium over the course of a year. As with all studies that rely on participants to recall their eating patterns, the accuracy of their recall is never guaranteed. In addition, it's possible that some other factor not accounted for in this study significantly affected the risk of colon cancer.
How does this affect you?
Do you need to eat more calcium? That depends on how much you normally consume. Optimal intake of calcium depends on your age, but for adults the Food and Nutrition Board of the National Academy of Sciences recommends 1000 to 1200 mg per day. The findings of this study suggest that for protection against colon cancer, 700-800 mg may be enough. But calcium serves many more purposes in the body, such as building strong bones and teeth, and helping with nerve and muscle function, including the heart muscle.
The findings of this study suggest that if you consume the recommend 1000 to 1200 mg of calcium per day, you'll have enough to prevent bone loss as you age and you may gain an added benefit of protection against distal colon cancer.
Foods with the most calcium include:
Calcium fortified foods, such as orange juice, breakfast cereals and cereal bars, tofu, and soy milk
And don't forget that vitamin D is important for helping your body absorb calcium. Milk is a great source of vitamin D, as is sunlight.
Wu K, et al. Calcium intake and risk of colon cancer in women and men. Journal of the National Cancer Institute
. March 20, 2002;94(6):437-446.
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a