New Study Confirms Calcium's Colorectal Cancer Prevention Properties

A recent study has revealed that calcium intake may be a powerful preventative against colorectal cancer.

In a past e-alert I told you about research at the Dartmouth-Hitchcock Medical Centre that showed how high calcium intake may significantly lower the risk of advanced polyps developing into cancer. That study indicated that calcium supplements (apart from dietary sources) provide effective protection against advanced polyps.  (Can Calcium Lower The Risk Of Colorectal Cancer?)

Around 34,500 people are diagnosed with colorectal cancer each year in the UK. Excluding non melanoma skin cancer, this makes colorectal cancer the second most common cancer affecting women (after breast cancer) and the third most common cancer of men (after prostate and lung cancer).

Now a new US study from the University of Minnesota confirms those earlier results, while shedding new light on the value of supplementing with calcium. But as well see, there are important guidelines that everyone who uses calcium supplements needs to be aware of.

To protect and defend

Researchers at the University of Minnesota (UM) used data collected from more than 45,000 women who completed National Cancer Institute food frequency questionnaires. None of the women had a history of colorectal cancer at the outset of the study.

In addition to tracking dietary sources of calcium, the researchers separated the subjects into four groups according to their intake of supplementary calcium:

• Zero calcium supplement intake: more than 25,400 subjects
• Zero to 400 mg daily: more than 9,400 subjects
• 401 to 800 mg daily: more than 4,100 subjects
• More than 800 mg daily: more than 6,200 subjects

Diet, supplement intake and medical records were followed for an average of 8.5 years. During that time, 482 women developed colorectal cancer.

As published in the January issue of Cancer Epidemiology, Biomarkers and Prevention, the UM team reported three key results:

• Compared with low calcium consumption (from either diet or supplements), subjects who consumed between 400 and 800 mg of calcium per day from any source reduced their risk of colorectal cancer by about 25 percent
  
• When calcium intake was more than 800 mg per day, colorectal cancer risk was reduced by more than 45 percent
  
• Women who consumed large amounts of calcium from BOTH dietary and supplemental sources had the greatest protection against colorectal cancer

These results, combined with earlier research (such as the Dartmouth-Hitchcock trial of more than 900 men and women), would indicate that high calcium intake may also act as a preventive against colorectal cancer in men.

Dynamic duo

Both the UM and Dartmouth-Hitchcock studies illustrate the importance of including plenty of calcium-rich foods in your diet, such as salmon, cabbage, kale, and yellow, green, or waxed beans.

In the Dartmouth-Hitchcock study, subjects also took 1,200 mg of calcium carbonate daily. HSI Panellist Dr Allan Spreen noted that calcium carbonate is the most common, most readily available and least expensive type of calcium supplement. But the carbonate form does have two drawbacks: Its not as well absorbed as some other inorganic forms of calcium, and it binds the most acid.

The latter problem presents a potential plus, as well as a minus. Some scientists believe that calciums ability to bind acids may be the very reason it protects against cancer. But binding digestive acids may also result in poor absorption of nutrients and indigestion. So if a 1,200 mg supplement of calcium is taken daily, along with good sources of calcium in the diet, keep an eye out for digestive problems, which can usually be managed by adjusting the dosage of the supplement.

In addition, Dr. Spreen notes that, Calcium is not found in nature (in edible form) without magnesium, and they therefore should always be given together.

Foods that are high in magnesium include leafy green vegetables, whole grains, bananas, apricots, meat, beans, and nuts.

Added prevention

And as long as we're on the subject of protecting the colon with supplements, I should also mention folate.

A 2002 study - also published in Cancer Epidemiology, Biomarkers, and Prevention - showed that those with a family history of colon cancer may cut their risk by as much as 50 percent with a supplement of 400 micrograms of folate daily. In addition to supplements, spinach and asparagus provide good sources of folate.

Whether or not you and your doctor decide that calcium and folate supplements are right for you, keep in mind one more important preventive measure: Ask your doctor about arranging for a colonoscopy, which is recommended every three to five years for everyone over the age of 50; especially those with a family history of colon cancer.