Colorectal Cancer Symptoms And Risk Factors

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Colorectal Cancer Fast Facts

If you're above 50 and your bowel habits have changed over the past few weeks, screen for colorectal cancer. You may have diarrhea or constipation and feel your bowel is not fully empty. Look out for narrow stool, bright red or black blood or excessive mucus in the stool. See if eating causes abdominal pain, bloating, and vomiting. The cancer is mostly caused by a red or processed meat-rich diet, alcoholism, tobacco smoking, genetic diseases, and spontaneous gene mutations.

Though often clubbed as colorectal cancer, colon cancer and rectal cancer are different. The causes, risk factors, and symptoms of both are more or less the same. But because of the different positions, structures, and functions of the colon and the rectum, the method of treatment is different.

A colon cancer is almost always treated with a surgery. Surgery is the last resort for rectal cancer patients. They are first treated with chemotherapy and/or radiation.

But the good news is: colorectal cancer is preventable.

Colorectal Cancer Symptoms

People aged 50 or above experiencing changes in bowel habits lasting more than a few weeks, pain or discomfort in the abdomen, and blood in stool should get a screening test.

Colorectal cancer or the cancer of the colon or the rectum is silent in most cases. The cancer can lurk anywhere in the 5–8 feet long passage and often doesn’t present any tell-tale symptoms in the initial stages of the cancer.

In an advanced stage, the symptoms of colorectal cancer include:

  • Change in bowel habits: You may notice a change in your bowel habits, which may last more than a few weeks. You may feel that your bowel has not been emptied entirely and you might try more often.
  • Change in bowel movement: You may pass watery stool like in diarrhea or have difficulty passing stool, leading to constipation. The stool might itself become narrow because of blocks in the colon and the rectal passage.
  • Blood in stool: If you don’t have piles or irritable bowel disorders, persistent blood in your stool or toilet bowl after a bowel movement is a matter of concern. Bright red blood may indicate a cancer in the rectum or in the last part of the colon, while dark or black stool indicates a cancer higher up in the colon. You may notice a high amount of mucus in the stool too.
  • Mucus in the stool: Some amount of mucus in your stool is not uncommon. But a persistently large amount of mucus in the stool, along with blood or change in bowel habits, indicates there’s an infection or inflammation your body is trying to cure.
  • Bowel obstruction: You may experience pain, discomfort, bloating, nausea, and vomiting after eating. The symptoms may be present at every meal over a few weeks. This doubtlessly reduces appetite and food intake, leading to weakness, fatigue, and weight loss.

Piles, IBS, and IBD Have Similar Symptoms

Colorectal cancer might be all the more difficult to detect because it shares similar symptoms as certain other conditions. .

  • Piles or hemorrhoids also cause bleeding during bowel movement.
  • Irritable bowel syndrome (IBS) can cause diarrhea, constipation, and abdominal cramping.
  • Irritable bowel disorders, like ulcerative colitis and Crohn’s Disease, have symptoms like abdominal pain, diarrhea, and bleeding. Patients often complain that they haven’t been able to empty the bowel completely and feel the need to try again and again. These patients also suffer weight loss.

This is what makes screening for colorectal cancer so crucial after 50.

Detection Of Colorectal Cancer

Get a colonoscopy or fecal occult blood test once you turn 50.

Screening tests are mandatory once you turn 50. This is the average age when the disease starts showing itself. Go for colonoscopy and tests to detect occult or hidden blood in stool, even when you can’t see any trace of blood with the naked eye.

The colonoscopy will find if there are polyps or abnormal tissue growths in your colon. These are the precursors to the cancer. Further tests can determine whether these polyps are benign or malignant.


It is the third most common cancer worldwide, making up 9% of all cancer incidences, and fourth most common cause of death. It is also common among black men.

Colorectal cancer is the third most common cancer worldwide, accounting for 9% of all cancer incidences, and the fourth most common cause of death.1

It is slightly more common in men, and black men at that. Over the last decade, both the incidence and the mortality rate have come down.2 But it is predicted that 2.4 million cases will be diagnosed annually by 2035, affecting 1.36 million men and 1.08 million women.3

Age Of Onset

Male or female, you are at a high risk of colorectal cancer once you cross 50. The chances of diagnosis rise progressively after you turn 40 and sharply after you turn 50. In fact, 90 out of 100 people with colorectal cancer are 50 or older. Of these, there are 50 times more people in the 60–79 age bracket than in the 40 or below bracket.

50 is the crossover age, with 90% of colorectal cancer patients 50 years or older. But it’s becoming common among the younger generation.

There are two reasons for colorectal cancer showing up in your middle age:

  • First, gene mutation requires a long-term exposure to physical, chemical, and biological risk factors.
  • Second, by the time you hit 50, your cell repair mechanism has become weak.

As a result, there’s an increase in new colorectal tissue growths, both benign and malignant. There’s a delay in the death of these cells. So the cancer grows and spreads rapidly.4

However, even as the incidence rate is dropping, this cancer is becoming common among the younger generation. This is possibly because of greater exposure to environmental or lifestyle risk factors. Children are not entirely immune either if there’s a family history of colorectal cancer, colon tumors, and Lynch syndrome.

Colorectal Cancer Risk Factors

Genetic Conditions

About 20% of colorectal cancer patients have a family history of the cancer.

Colorectal cancer is mostly environmental in nature. Long exposure to environmental risk factors makes the DNA mutate suddenly in a few places and trigger the growth of cancerous cells. But genes also play a big role.

Up to 20% of colorectal cancer patients report that they have family members with colorectal cancer. Of these, 5 to 10% have two hereditary cancer-causing conditions: familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC). The rest of the patients and their family get colorectal cancer due to shared environmental factors.


If even one parent has benign tumors in the colon, a genetic condition known as familial adenomatous polyposis, there’s at least a 50% chance of your getting the condition. If not treated, FAP always progresses to colorectal cancer.

A person with classic FAP develops colorectal cancer when they are about 39 years of age.

In the classic form of the disease, the polyps start developing when you are in your mid-teens. If this is not treated, you may have more than a 100 polyps by the age of 39. This is the average age a person with the classic FAP develops colon cancer.

Sometimes, the development of the polyps may be delayed. This is called attenuated FAP. In this case, your colorectal cancer onset may get postponed till you are 55.5

HNPCC Or Lynch Syndrome

Say your sibling has been diagnosed with Lynch syndrome or hereditary nonpolyposis colorectal cancer (HNPCC). Because you hail from the same set of parents, one of whom obviously has this condition, you also have a 50% increased risk of inheriting Lynch syndrome.

People with Lynch syndrome are mostly diagnosed with colorectal cancer when they are 45.

It doesn’t present any symptoms in itself but makes you vulnerable to a number of cancers, chiefly of the colon and the rectum.

If you are a woman, Lynch syndrome also puts you at risk of uterine and ovarian cancer.

Lynch syndrome accounts for about 3 to 5% of the total incidences of colorectal cancer in the United States. If you have it, you would probably be diagnosed with colorectal cancer at 45, much earlier than the average 72 in the general population.6 7

Lifestyle Risk Factors

About 75% of all colorectal cancers are caused by sporadic gene mutations and environmental risk factors.8

The Wrong Type Of Diet

1. Frequent Consumption Of Red Meat

Pork, beef, veal, and lamb contain heme iron, which increases the risk of colorectal cancer.

Red meat adds to your risk of colorectal cancer, especially colon cancer. When heated at a high temperature, these animal fats and proteins break down into certain cancer-causing amines and hydrocarbons. Moreover, red meat like pork, veal, beef, and lamb contain heme iron, which is associated with a higher risk of colorectal cancer.

2. Huge Amounts Of Processed Meat

People who eat the maximum amount of processed meat have a 17% higher risk of colorectal cancer than those eat it rarely.

Processed meat is even more unsafe. If you live on processed meat, you are 17% more likely to get colorectal cancer than those who eat it rarely.9 This is one of the reasons this cancer is so common in affluent and developed countries.10

3. Insufficient Vegetables And Leafy Greens

Plant antioxidants and vitamin B9 or folate can prevent cancer.

Fibrous vegetables or fruits with antioxidants like flavonoids and caroteniods keep your colon healthy. Leafy greens contain vitamin B9 or folate, which prevents cancer.11 A lack of these may not cause the cancer, but will reduce your chance of prevention. Are you including these anticancer foods in your diet?

Alcohol Consumption

If you drink more than 3.5 drinks, or 50 g, a day, you are 52% more likely to get colorectal cancer. The risk increases by 7% for every 10 g.

Onset of cancer, especially in the last part of the colon, is earlier in people who drink than in the general population.12 Sadly, this is true even for light drinkers.

Alcohol breaks down into acetaldehyde, which accumulates in the colon and degrades the folate vitamin in the mucosal cells lining the inside of the colon, by up to 48%.13The acetaldehyde further damages the DNA and generates reactive molecules called free radicals that damage cells and increase the risk of cancer. Acetaldehyde may also function as a solvent and help cancer-causing molecules penetrate the mucosal cells of the colon.

Don’t Have More Than 2 Drinks A Day

The American standard for 1 drink is 14 g – that is 12 oz can of beer or a regular 5 oz pouring of wine, or a standard shot of 1.25 oz tequila, rum, or vodka. The US Department of Health and Human Services and the US Department of Agriculture suggests that women should have no more than 1 drink a day and men no more than 2.14

You have a 21% increased risk of colorectal cancer if you drink more than 2 drinks. Any more than 3.5 drinks a day, you are 52% more likely to get colorectal cancer. For every 10 g you pour down your throat, your cancer risk leaps by 7%. You can detox your colon with this juice.

East Asians have a higher risk of getting cancer from alcohol due to mutation in the gene that controls alcohol metabolism. It makes the alcohol-breaking enzyme overactive. So more toxic acetaldehyde accumulates in the colon. Another gene mutation hinders the conversion of the acetaldehyde into non-toxic substances.15

Smoking Tobacco

In the United States, 12% of the colorectal cancer deaths are due to tobacco smoking.

You already know that smoking tobacco and your lungs are sworn enemies. But did you know that smoking makes your colon and rectum vulnerable to cancer too? In the United States, of every 100 casualty of this disease, 12 have smoking to blame.16

A Norwegian study reports that women who smoke are 20% more likely to get colon cancer than their counterparts who have never smoked.17

Nicotine Spreads The Cancer

Tobacco contains carcinogenic substances like nicotine and its compounds, including NNK. These can induce cancer cell growth and make the cells metastasize or travel across the body, affecting other areas.18

The risk decreases when you quit smoking. And the younger you quit, the better.19

Sadly, even passive smokers can get colorectal cancer and earlier than others. In their case, the screening test should be done at 40.20

Physical Inactivity And Overweight

About 25 to 33% of colorectal cancer incidences are caused by physical inactivity and excess body weight.

Does the right diet and no smoking or boozing always reduce your risk of getting colorectal cancer? Not if you don’t exercise, have excess body weight, and a protruding belly.

Physical inactivity and excess body weight together account for about 25 to 33% of colorectal cancer incidences, and overweight men have a higher risk of colon cancer than overweight women.21

This can be changed. Moderate or intense exercising, both related to your work and what you do in your leisure time, can reduce the risk of colon cancer by 13 to 41%.22 Exercise increases the metabolic rate and oxygen intake and improves the stretching and contraction of the gut muscles.

Diseases And Conditions

If you have ulcerative colitis and Crohn’s Disease, stay alert. There’s a 4 to 20 times risk of the inflammatory condition worsening into colorectal cancer.23

References   [ + ]

1. Haggar, Fatima A., and Robin P. Boushey. “Colorectal cancer epidemiology: incidence, mortality, survival, and risk factors.” Clinics in colon and rectal surgery 22, no. 04 (2009): 191-197.
2. Colorectal Cancer Rates by Race and Ethnicity. Centers for Disease Prevention and Control.
3. Colorectal Cancer Statistics. World Cancer Research Fund International.
4. Patel, Bhaumik B., Yingjie Yu, Jianhua Du, Edi Levi, Phillip A. Phillip, and Adhip PN Majumdar. “Age-related increase in colorectal cancer stem cells in macroscopically normal mucosa of patients with adenomas: a risk factor for colon cancer.” Biochemical and biophysical research communications 378, no. 3 (2009): 344-347
5. Familial Adenomatous Polyposis. Genetics Home Reference.
6. Lynch Syndrome. Cancer.Net.
7. Lynch Syndrome. Conquer Cancer Foundation.
8. Peppone, Luke J., Martin C. Mahoney, K. Michael Cummings, Arthur M. Michalek, Mary E. Reid, Kirsten B. Moysich, and Andrew Hyland. “Colorectal cancer occurs earlier in those exposed to tobacco smoke: implications for screening.” Journal of cancer research and clinical oncology 134, no. 7 (2008): 743-751.
9. Food Types and Bowel Cancer. Cancer Research, UK.
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11. Qin, Tingting, Mulong Du, Haina Du, Yongqian Shu, Meilin Wang, and Lingjun Zhu. “Folic acid supplements and colorectal cancer risk: meta-analysis of randomized controlled trials.” Scientific reports 5 (2015).
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14. What Is A Standard Drink?. National Institute on Alcohol Abuse and Alcoholism.
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17. Gram, Inger T., Tonje Braaten, Eiliv Lund, Loic Le Marchand, and Elisabete Weiderpass. “Cigarette smoking and risk of colorectal cancer among Norwegian women.” Cancer Causes & Control 20, no. 6 (2009): 895-903.
18. Alcohol and Cancer Risk. National Cancer Institute.
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20. Peppone, Luke J., Martin C. Mahoney, K. Michael Cummings, Arthur M. Michalek, Mary E. Reid, Kirsten B. Moysich, and Andrew Hyland. “Colorectal cancer occurs earlier in those exposed to tobacco smoke: implications for screening.” Journal of cancer research and clinical oncology 134, no. 7 (2008): 743-751.
21. Larsson, Susanna C., and Alicja Wolk. “Obesity and colon and rectal cancer risk: a meta-analysis of prospective studies.” The American journal of clinical nutrition 86, no. 3 (2007): 556-565.
22. Brown, Justin C., Kerri Winters‐Stone, Augustine Lee, and Kathryn H. Schmitz. “Cancer, physical activity, and exercise.” Comprehensive Physiology (2012).
23. Haggar, Fatima A., and Robin P. Boushey. “Colorectal cancer epidemiology: incidence, mortality, survival, and risk factors.” Clinics in colon and rectal surgery 22, no. 04 (2009): 191-197.