A new study in the New England Journal of Medicine says it prevents an average 40% of all colon cancers.
This 22 year study questioned nearly 90,000 health care professionals: more than 30,000 women, nearly 60 thousand men.
Every two years, they reported on their own colon cancer screening results.
The study says colonoscopies -- using a lighted flexible tube to visualize the entire colon -- made the biggest difference: a 56% reduction in colon cancer diagnosis.
A similar procedure – sigmoidoscopy, which only checks the lower colon -- lowered risk by 40%.
Yearly stool tests for hidden blood decreased cancer risk by more than a third.
But, at 56% colon cancer risk reduction, colonoscopy is best.
The U-S Preventive Services Task force recommendation for all adults 50 to 75:
Nobody looks forward to a colonoscopy. It takes time. And the prep is miserable. But vital.