Dr. Mehmet Oz. — Photo by Art Streiber

I understood the importance of colon cancer screening for both men and women, but I had no other risk factors. I'm not overweight; I don't smoke; my diet consists mostly of high-fiber, low-fat foods; and I have no family history of colon cancer. I probably would have delayed the screening for months, except that I'd committed on my television show to undergoing the test. So I was shocked when my gastroenterologist found an adenomatous polyp, the kind that sometimes develops into cancer. More than 50,000 Americans will die of colon cancer this year. My doctor told me my good health habits undoubtedly lowered my risk, since he found only one polyp. But simply doing what I was told to do at 50 — get a colonoscopy — allowed me to have the polyp removed and possibly dodge a bullet. If I had waited, the consequences could have been severe.

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But now what? Colon cancer screenings are certainly not a onetime deal. When should you get your second colon cancer screening, or your third? To my surprise, the guidelines are anything but straightforward. I found seven approved protocols for follow-up screenings.

My second colonoscopy was just three months later — but that's because I'd been cavalier about the bowel prep the first time, and the surgeon wanted to be sure he hadn't missed anything. The second time around, I maintained a clear-liquid diet for 24 hours before the procedure.

For most people with one or two small, precancerous polyps, including me, the next colonoscopy should be in five years (three years for bigger polyps or multiple polyps). For people with benign polyps or no polyps, a colonoscopy is recommended every 10 years.

But don't miss that first one — at age 45 for African Americans, and age 50 for most others. Evidence suggests the first colonoscopy has the biggest effect on reducing the incidence of colon cancer in patients with precancerous polyps.

Vitamin D May Lower Cancer Risk

Don't skimp on vitamin D: Low levels may be linked to colon cancer. One theory is that cells need vitamin D to undergo a process called apoptosis — or programmed cell death. If a cell goes awry (becomes precancerous), it normally will kill itself. If it doesn't, it can become cancerous. To boost your vitamin D levels, I recommend that everyone get 10 minutes of sun exposure a day, plus 1,000 international units of vitamin D3 as a supplement.

                                Originally published in the March/April 2011 issue

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