'Most young people ignore them': Harvard liver doctor warns of 7 early signs of colon cancer as 'cases double under age of 55'

According to an analysis published by the American Cancer Society, colorectal or colon cancer has become the leading cause of cancer-related death among people under the age of 55, with rates rising significantly despite a decline in older adults. Since the life-threatening disease often progresses silently, recognizing early warning signs and adhering to updated screening guidelines have become vital for timely diagnosis and effective treatment. Dr. Saurabh Sethi, a gastroenterologist trained at AIIMS, Harvard, and Stanford, shared a video on YouTube, highlighting 7 early warning signs of colon cancer that many people tend to ignore.

Colon cancer early signs: 7 symptoms you should never ignore

Persistent change in bowel habits

As per Dr Sethi, the first sign is a change in your bowel habits: constipation, diarrhea, or alternating between the two. Everyone gets these once in a while. A week of diarrhea after a bad meal, a few days of constipation when you travel, that is normal. What's not normal is when the change persists for more than a few weeks with no obvious explanation.


Your colon's main job is to absorb water and form stool. When a tumor grow, it disrupts that process. If the tumor irritates the bowel lining, transit speeds up and you get chronic diarrhea. If it blocks the passage, stool slows down, and you get constipation. And when the obstruction is partial, you get the alternating pattern. So, if your gut rhythm has changed and stayed changed for more than 3 to 4 weeks with no diet shift, no travel, no new medication to explain it, get evaluated.

Bright red blood in stool

The most common cause of bright red blood in your stool, on the toilet paper, and in the toilet bowl is actually hemorrhoids. Sometimes it's small tears called fissures, both benign. As per Dr Sethi, 9 times out of 10, a person will dismiss it, saying it's just hemorrhoids. But any blood, even once, deserves an evaluation because every spot of blood needs to be ruled out. If you've seen it once, book the appointment this week, not next.

Dark or black stools

Most people see it, glance at it, flush it, and never realize their body was sending them a warning, explains Dr Sethi. When the bleeding happens higher up in your GI system, like from the stomach or the small intestine, even the right side of your large intestine, by the time the blood travels all the way down and out, it's been broken down by digestive chemicals. It turns black.

Dark stools usually point to a problem higher up in the GI tract, but tumors in the right side of the colon, aka the ascending colon, can also produce dark stools because the blood has time to oxidize as it travels through. So, if you're seeing consistently dark or tarry stools and you have not recently eaten beets, taken iron supplements, or used Pepto-Bismol, get it evaluated.

Unintentional weight loss

Unintentional weight loss, without changing your diet, without changing your lifestyle, without starting any exercise regimen, can be a cause of concern, states Dr Sethi. The tumor physically interferes with how your intestine absorbs nutrients. So even if you're eating the same amount, you're absorbing less. Second, cancers release substances called cytokines that hijack your metabolism and redirect nutrients towards the tumor's growth. So if you're losing weight without trying and you can't point to a clear reason, that is not a win. That is a signal.

Persistent bloating and gas

It is the feeling that your stomach is twice the size it should be by the end of the day. The dismissal is universal: IBS, lactose intolerant, gluten and most of the time that's actually true, admits Dr Sethi before adding that tumors in the colon can cause bloating through 3 different mechanisms. They physically block gas behind them and disrupt the bacteria in your gut.

By slowing down the passage of waste, they give bacteria more time to ferment food, which produces even more gas. So, if you've been bloated for more than a few weeks and you have not changed your diet, your stress levels, or your medications, that is not normal and deserves a real workup.

Tenesmus or incomplete evacuation

Dr Sethi shares that this sign has a medical name most people have never heard of. It's the constant feeling that you still have to go to the bathroom even right after you just went, as if your bowels are never quite empty. As that tumor grows, it presses on the bowel wall and mimics the sensation of stool sitting right there even when there is nothing left to pass. So your brain keeps telling you to go. Most people assume it's IBS or that they need more fiber or they're just dehydrated. If it persists for several weeks, especially alongside any of the other above signs, you should take it seriously.

Iron deficiency or anemia

According to Dr Sethi, some colon tumors don't cause visible bleeding at all. Instead, they ooze a tiny amount of blood every day. So little that it doesn't change the color of your stool. But over weeks and months, that constant low-level blood loss slowly drains your body's iron reserves. Your hemoglobin drops, your red blood cells can't carry oxygen properly, and what you feel is exhaustion, brain fog, cold hands and feet, and shortness of breath while walking up the stairs.


Dr Sethi adds that most young women, when they hear iron deficiency anemia, they assume it's their period while most young men get told they're training too hard or eating too little red meat. So they take a supplement and move on. But any man with iron deficiency anemia needs to have colon cancer ruled out. And any woman with iron deficiency anemia that's out of proportion to her cycle or doesn't respond to supplementation needs the same workup. They should get the colonoscopy done.