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What Can Calcium Do for My Colon?


Updated July 23, 2012

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Question: What Can Calcium Do for My Colon?

My mother heard that she should be supplementing with calcium daily to reduce her risk of colon cancer. Why is that?


Calcium is a mineral with many important roles in your body, including the support of your bones and teeth. Some research suggests that calcium can reduce the risk of polyp formation, and therefore decrease the risk of developing colorectal cancers over time. However, calcium supplementation is not encouraged for everyone. Before your mother starts taking calcium, she should discuss her concerns with her doctor and learn more about this important mineral.

The role of calcium in colorectal cancer prevention is not a new one, although many studies have inconclusive results. Currently, science cannot definitively prove that taking calcium supplements daily will reduce your risk of colon cancer. In fact, both the National Cancer Institute and the American Cancer Society discourage supplementation with this mineral unless you are instructed to do so by a physician.

According to the National Cancer Institute, some studies have shown between a 20-45% reduction in cancers of the distal colon and rectum with calcium supplementation. Other studies show that it may actually increase the risk of developing prostate cancer in men.

There are two schools of thought regarding calcium and its preventive role in colon cancer. Some studies conclude that the mineral slows the rapid division of cells in your colon, which is what leads to polyp formation. Other experts believe that the calcium helps by binding with caustic substances, such as bile or fats, and helps to remove them from your colon quickly.

What Else Can Calcium Do?

Aside from decreasing your risk of osteoporosis and cavities, this mineral can carry an electric charge, making it an important electrolyte that helps your nerves and muscles (including the heart) function properly. Its functions in your body don't end there -- calcium also plays an important role in blood clotting and maintaining your pH balance.

Natural Sources of Calcium

Barring a history of osteoporosis, celiac disease, lactose intolerance or a vegan diet, most healthy adults obtain this mineral through a balanced diet. However, some practitioners believe women need more than just dietary calcium to prevent osteoporosis.

You might already know that dairy products, such as milk or cheese, are excellent sources of both calcium and vitamin D. There are many other natural sources of this mineral, including:

  • Dark green leafy vegetables, like spinach or kale
  • Tofu
  • Almonds
  • Egg yolks
  • Legumes
  • Oysters and shellfish

This mineral is also present in many over-the-counter antacids and digestive aids. When in doubt, read the label and look for the different forms of calcium, including:

  • Calcium carbonate
  • Calcium citrate
  • Calcium gluconate

Calcium Absorption

Calcium requires the presence of vitamin D to be absorbed and used by your body. This means that you can eat all the calcium you like, but without vitamin D to activate it, it's useless.

Most people get all the vitamin D they need through about 15 minutes a day of sunshine exposure. Despite this, vitamin D deficiency continues to be a major problem in the U.S. and abroad and can lead to serious problems, such as osteoporosis and easily broken bones. When UV light rays hit your skin, vitamin D precursors in your skin are transformed into the active form of vitamin D. This means that your body makes vitamin D through a process called synthesis. If you live in a perpetually overcast region, some vitamin D can be obtained through the diet and is found in fortified foods, salmon, dairy and cod liver oil.

When You Don't Get Enough

The best-known effect of a calcium deficiency involves your bones. Without calcium to strengthen them, bones can become brittle and break easily. You may become more susceptible to cavities in your teeth, as well. Aside from your bones, a calcium insufficiency may lead to problems clotting your blood or even heart and muscle tone problems, which can be deadly. If your doctor is concerned about your calcium level, he or she can order a simple blood test to check it.

Side Effects of Taking Too Much

Just because you can find rows of over-the-counter calcium supplements does not mean you can take it without risk. This mineral is removed from your body through the kidneys. When you take in too much calcium, it can be hard on your kidneys and result in kidney stones or, in extreme cases, kidney failure. Many people suffer bloating and constipation after taking this mineral, which is why different calcium preparations (such as chewable and liquid forms) are available to make calcium easier to take.


American Cancer Society. (2006). American Cancer Society’s Complete Guide to Colorectal Cancer. Clifton Fields, NE: American Cancer Society.

American Cancer Society. (n.d.). Can Colorectal Cancer Be Prevented? Accessed July 10, 2012.

National Cancer Institute. (n.d.). Calcium and Cancer Prevention: Strengths and Limits of the Evidence. Accessed July 11, 2012.

Office of Dietary Supplements. (n.d.). Vitamin D. Accessed July 12, 2012.

PubMed.gov. (2004). Dairy Foods, Calcium, and Colorectal Cancer: A Pooled Analysis of 10 Cohort Studies. Accessed July 12, 2012.

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