Vitamin D Seems to Thwart Colorectal Cancer

It's just one of several steps people can take to protect themselves

TUESDAY, Dec. 9, 2003 (HealthDayNews) -- A new study offers further guidance on what people should -- and shouldn't -- be doing to avoid getting colon cancer, or at least the polyps that can lead to the cancer.

First, don't smoke, and don't drink alcohol excessively.

Second, do eat enough cereal fiber and vitamin D. Both of these appear to reduce your risk.

The good news is the information in the study, which appears in the Dec. 10 issue of the Journal of the American Medical Association, doesn't differ appreciably from what experts already knew.

"There's nothing to lead to significant alterations in current recommendations," says Dr. Durado Brooks, director of colorectal cancer at the American Cancer Society.

The most important piece of new information concerns vitamin D.

"Because of the interplay between calcium and vitamin D, it has been difficult to tease out what was important. And this study goes a good ways toward strongly suggesting that vitamin D is an important protective factor, while the calcium question still remains somewhat open," Brooks says.

Colorectal cancer -- or cancer that begins in either the colon or the rectum -- is the second-leading cancer killer in the United States. Because virtually all colorectal cancers start as polyps, the key is to find these abnormal growths before they become malignant. It is thought that screening, along with lifestyle factors, could prevent many of the 57,000 deaths caused by colon cancer each year.

The new study looked at 3,121 people aged 50 to 75 from 13 Veterans Administration medical centers across the country. All the participants were symptom-free; almost all were men.

Each person was first given a screening colonoscopy to detect the presence of polyps.

"About 10 percent had serious colon polyps, the kind that could develop into cancer over time," says Dr. David Lieberman, lead author of the study and the chief of gastroenterology at Portland VA Medical Center in Oregon. "We have evidence that if we detect and remove polyps we can actually prevent most cancers. This data emphasizes the importance of getting screened when you feel perfectly fine."

The study participants also gave detailed information regarding family history of colon cancer as well as diet and exercise.

Those who had a first-degree relative with colorectal cancer had a 66 percent increased risk of polyps, while those who currently smoked had an 85 percent increased risk. People who currently drank at least seven alcoholic drinks a week had a slightly increased risk.

On the positive side, participants who consumed more than 4.2 grams of cereal fiber a day had a lower risk of serious colon polyps, as did those who took a daily aspirin and more than 645 international units of vitamin D each day. Physical activity, daily multivitamins and calcium had smaller positive effects. Overall, though, the effects were mild.

Although the study didn't definitely prove that these factors changed the risk of cancer, they do point to relatively painless action people can take to improve their odds.

Those steps are: regular exercise, multiple vitamins and the addition of more fiber and vitamin D in your diet. Vitamin D can be found naturally in cod liver oil, salmon, mackerel, sardines and fortified milk. You can also get the optimal amount by taking a multivitamin and a calcium/vitamin D supplement, Lieberman says.

People should not take daily aspirin without consulting their doctor first.

There are also things people can refrain from doing that could change their risk.

"Stopping smoking and reducing red meat consumption would be beneficial," Lieberman says. "The other message is that if you do have a family history of colon cancer, you need to talk to you doctor about when to start screening and preferably be screened with a colonoscopy."

More information

For more on colorectal cancer, visit the National Cancer Institute or the American Cancer Society.

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