Color-Blind People May Not Notice That They’re Bleeding!

Unusual bleeding or discharge is one of the classic seven warning signs of cancer. Blood in the stool could be a sign of colon cancer. It’s also a common sign of diverticulosis of the colon. Unfortunately, people with red-green color blindness might not notice that they are passing blood with their bowel movements. Here’s an article about three color-blind men who didn’t notice that they were passing blood with their stool. One of them had colon cancer. Another had diverticulosis; he was bleeding heavily but mistook the blood for diarrhea. The third patient had bleeding from hemorrhoids. The men didn’t notice the blood because they can’t see the color red. Fortunately, their wives saw the blood and had them seek medical attention.

Red-green color-blindness is far more common in men than in women. That’s because men have only one copy of the X chromosome in each of their cells. If one of the genes on their X chromosome is defective, they don’t have a spare X chromosome to serve as a backup. Women don’t get red-green color-blindness unless they inherit a defective version of the gene from both parents. That’s why women rarely get red-green color-blindness, but even a woman with normal color vision can have color-blind sons.

Fortunately, the intestinal problems that these men had are preventable by diet. Colon cancer is rare in populations that eat a low-fat, plant-based diet. So are diverticulosis and hemorrhoids, which result from constipation.


Note: Since I wrote this post, glasses that correct for red-green colorblindness have become available!