Colorectal Cancer Symptoms And Risk Factors

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Colorectal Cancer Symptoms

Colorectal cancer has symptoms like rectal bleeding, changed bowel habits, narrow stool, abdominal cramps, nausea, and weight loss, which are similar to those of IBS and Crohn's disease. Testing for abnormal tissue growth and blood in stool is mandatory after 50. The cancer is mostly caused by factors like red or processed meat-rich diet, alcoholism, and tobacco smoking, and even by a genetic condition called Lynch Syndrome.

Cancer is a coup d’etat. One cell turns rogue, multiplies vigorously to populate its ranks, overwhelms your internal security forces, and takes your own body hostage, often so silently that you might stay blissfully unaware until overthrow is imminent.

Colorectal Cancer

It is the third most common cancer worldwide and fourth most common cause of death.

Colorectal cancer is silent in most cases. This cancer of the colon or the rectum that can lurk anywhere in the 5–8 feet long passage often doesn’t present any tell-tale symptoms. Probably, that’s why it remains the third most common cancer worldwide, accounting for 9 percent of all cancer incidences, and the fourth most common cause of death.1

Colon Cancer And Rectal Cancer

Though they are often clubbed as colorectal cancer, colon cancer and rectal cancer are different, not so much in the causes and risk factors but in the treatment because of their different anatomy and functions. While a colon cancer is almost always treated with a surgery, rectal cancer requires chemotherapy and/or radiation before the surgery, which is often the last resort because of its painful nature.


It is more common among black men.

Colorectal cancer is slightly partial to men, and black men at that, than women. Over the last decade, both the incidence and mortality rates have come down,2 but in spite of that, statistics predict that 2.4 million cases will be diagnosed annually by 2035, affecting 1.36 million men and 1.08 million women.3


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

Screening tests are mandatory once you reach the average age when the disease starts showing itself, that is as soon as you turn 50. You’d need to go for colonoscopy and tests to detect blood in stool, even when you can’t see any trace of blood with the naked eye.

The colonoscopy will find if there are abnormal tissue growths in your colon, called polyps, which are what the cancer always begins as. Further tests can determine whether these polyps are benign or malignant.

Symptoms Of Colorectal Cancer

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

The symptoms rarely manifest before the cancer reaches an advanced stage or are similar to IBS, ulcerative colitis, or Crohn’s Disease.

  • A change in bowel habits lasting more than a few days. 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 colorectal passage
  • Bright red blood in your stool or in the toilet bowl after a bowel movement, which indicates a cancer in the rectum or in the last part of the colon
  • Dark or black stool, which indicates bleeding higher up in the colon
  • Mucus in the stool
  • Cramps or a sense of discomfort in the lower abdomen
  • An urge to take a dump even when the bowel is empty
  • Decreased appetite, leading to weakness and fatigue
  • Unintended weight loss in an effort to fight the cancer

Beware, Other Conditions Have Similar Symptoms

Colorectal cancer might be all the more difficult to detect because it shares similar symptoms as certain other conditions. This is what makes screening for colorectal cancer, especially once you’ve turned 50, so crucial.

  • The bleeding might be mistaken as caused by hemorrhoids.
  • The diarrhea or constipation might be thought to have been caused by irritable bowel syndrome or IBS, which also causes abdominal cramping.
  • Irritable bowel disorders, like ulcerative colitis and Crohn’s Disease, have symptoms like abdominal pain, diarrhea, bleeding, urge to defecate, sense of incomplete emptying of the bowel, and weight loss.

What Puts You At Risk For Colorectal Cancer?


About 5 to 10 percent of colorectal cancer cases are due to hereditary conditions like FAP and Lynch Syndrome.

Though colorectal cancer is mostly environmental in nature, as it is caused by sporadic mutations in your DNA at irregular intervals or only in a few places and after a long exposure to environmental risk factors, you may also curse your genes.

Up to 20 percent of colorectal cancer patients have reported having family members affected by the disease. Of these, 5 to 10 percent have two hereditary conditions as recognized cancer-causing factors, familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC). The remaining is due to shared environmental factors.


If you have a parent with benign tumors in the colon, a genetic condition known as familial adenomatous polyposis, there’s at least a 50 percent chance of your getting the condition too, which, if untreated, will almost certainly lead to colorectal cancer.

In the classic form of the disease, the polyps start developing when you are in your mid-teens, and if untreated, by the time you are 39, you may have more than a 100 of them. This is also the average age a person with the classic FAP develops colon cancer.

If the development of the polyps are delayed, in a case of attenuated FAP, your colorectal cancer onset can be delayed till you are 55.4

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 percent increased risk of inheriting the condition. It doesn’t present any symptoms in itself but makes you vulnerable to a number of cancers, chiefly of the colon and the rectum, and also of the uterus and the ovaries, if you are a woman. Lynch syndrome accounts for about 3 to 5 percent of the total incidences of colorectal cancer in the United States. If you have this condition, you would probably be diagnosed with colorectal cancer at 45, much earlier than the average 72 in the general population.5 6


50 is the crossover age, with 90% of colorectal cancer patients 50 years or older.

With a long-term exposure to physical, chemical, and biological factors that increase the risk of gene mutation and with the cell repair mechanism compromised by age, in most cases, cancer strikes when you are past your prime.

There are many more new colorectal tissue growths, both of the benign and the malignant variety, a rapid increase in the number of cancerous cells, and delayed cell death.7

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

However, even as the incidence rate is dropping, this cancer is becoming common among the younger generation, possibly because of greater exposure to environmental or lifestyle risk factors.

Lifestyle Risk Factors

About 75 percent of all colorectal cancer incidents are caused by sporadic gene mutations, without a hereditary basis, and environmental risk factors.8

Diet And Nutrition

Frequent Helpings Of Red Meat

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

You might justify your plateful of red meat as your protein fix, but it’ll all add to your risk of colorectal cancer, especially colon cancer.

When heated at a high temperature, the animal fats and proteins break down into certain amines and hydrocarbons that have carcinogenic properties.

Moreover, red meat like pork, veal, beef, and lamb contain heme iron, which scientists associate with a higher risk of colorectal cancer.

Loads 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.

You’d do worse to fry up a few rashers of bacon for breakfast, add that extra slice of ham to your sandwich on the go, or layer your bread with tinned meat for an easy meal. Processed meat is even more unsafe. If you live on processed meat, you are 17 percent 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

Not Enough Veggies And Leafy Greens

Vitamin B9 or folate is known to prevent cancer.

But you do not have to go all vegetarian if you don’t want to. You can still feast on chicken and turkey. Just make it a point to add fibrous veggies or fruits with antioxidants like flavonoids and caroteniods to every meal to keep your colon healthy.

Also keep your vitamin B9 or folate content adequate with lentils and leafy greens. Folate is known to be chemopreventive.11

Alcohol Consumption

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

Your bad habits are bad for a reason. The American standard for 1 drink is 14 g, which is equivalent to 12 oz can of beer, 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 a woman should have no more than 1 drink a day and a man no more than 2 drinks a day.12

Going Beyond 1 Drink A Day

If you are in the habit of knocking down more than 3.5 drinks, that is more than 50 g, a day, you are 52 percent more likely to get colorectal cancer as opposed to 21 percent if you drink more than 2 drinks a day. And for every 10 g you pour down your throat, your cancer risk leaps by 7 percent.

Sadly, this is true even for light drinkers. The cancer onset would be sooner than in the general population, and there might be a disproportionate increase in tumors in the distal or last part of the colon.13

Alcohol Damages The DNA

Alcohol breaks down into acetaldehyde, which accumulates in the colon and degrades the folate vitamin in the mucosal cells, even up to 48 percent,14 damages the DNA, and generates free radicals that cause excessive oxidation, leading to cell damage. It may also function as a solvent and help cancer-causing molecules penetrate the mucosal cells of the colon.

People Of Asian Ethnicity Are Worst Hit

The Japanese, Chinese, and Koreans have a genetic mutation that increases the ill effects of alcohol.

You need to be doubly careful if you are Chinese, Korean, or especially Japanese, because the gene that controls alcohol metabolism is mutated in them and makes the alcohol-breaking enzyme (alcohol dehydrogenase) super-active and loads up the acetaldehyde content in your colon. You have it worse if a defect in your genes does not allow the acetaldehyde to be converted into non-toxic substances. If alcohol gives you a racing heart and a flushed face, do not succumb to peer pressure for even another thimbleful.15

Smoking Tobacco

In the United States, 12% of the colorectal cancer victims have tobacco smoking to blame.

You needn’t be told that tobacco smoking kills. You already know that the cigarette and your lungs are sworn enemies. What you perhaps don’t know is 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

Nicotine Spreads The Cancer

Nicotine, found in tobacco, and many of its compounds, including NNK, are carcinogenic. These can induce cancer cell growth and make the cells travel across the body, which is a major cause of cancer-related death.17

The more years you put between yourself and your last smoke, the less your risk of cancer. And the younger you quit, the better.18

A Norwegian study reports that women who smoke are 20 percent more likely to get colon cancer than their counterparts who have never smoked, with more risks of colon cancer than rectal cancer.19

Passive Smoking Is No Less Risky

The cancer can catch up with you before you turn 50 if you are guilty of passive smoking.

Ironically, you can suffer from colorectal cancer even without smoking a single cigarette all your life. If you’ve lived under the pall of smoke belched out by your parents, siblings, or friends for long enough, cancer will catch up with you at a younger age. You would need to prepone the customary-at-50 screening tests by 5 to 10 years.20

Physical Inactivity And Overweight

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

Supposing you eat right and have ironclad rules about staying off tobacco and booze, does that 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 accounts for about 25 to 33 percent of colorectal cancer incidences, and overweight men are worse hit than women when it comes to colon cancer.21

This can be changed and, in fact, you should change it. Moderate or intense exercising, both related to your work or what you do in your leisure time, can reduce the risk of colon cancer by 13 to 41 percent22 by increasing the metabolic rate and oxygen intake and improving the stretching and contraction of the gut muscles.

Diseases And Conditions

If you have ulcerative colitis or Crohn’s Disease, your risk of colorectal cancer increases by 4 to 20 times.

Even if your doctor gives you a clean chit about the symptoms being caused by ulcerative colitis and Crohn’s Disease, you have reasons to stay alert. There’s a 4- to 20-fold risk of the inflammatory condition aggravating into colorectal cancer.23

And just because the symptoms of colorectal cancer manifest when you are 50 or older, don’t presume that children are entirely immune. If you have a family history of polyps or Lynch Syndrome, keep an eye on your child’s health.

References   [ + ]

1, 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.
2. Colorectal Cancer Rates by Race and Ethnicity. Centers for Disease Prevention and Control
3. Colorectal Cancer Statistics. World Cancer Research Fund International
4. Familial Adenomatous Polyposis. Genetics Home Reference
5. Lynch Syndrome. Cancer.Net.
6. Lynch Syndrome. Conquer Cancer Foundation.
7. 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
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.
10. Bastide, Nadia M., Fabrice HF Pierre, and Denis E. Corpet. “Heme iron from meat and risk of colorectal cancer: a meta-analysis and a review of the mechanisms involved.” Cancer prevention research 4, no. 2 (2011): 177-184.
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).
12. What Is A Standard Drink? National Institute on Alcohol Abuse and Alcoholism
13. Fedirko, V., Irene Tramacere, Vincenzo Bagnardi, M. Rota, L. Scotti, F. Islami, E. Negri et al. “Alcohol drinking and colorectal cancer risk: an overall and dose–response meta-analysis of published studies.” Annals of Oncology 22, no. 9 (2011): 1958-1972.
14. Homann, Nils, Jyrki Tillonen, and Mikko Salaspuro. “Microbially produced acetaldehyde from ethanol may increase the risk of colon cancer via folate deficiency.” International journal of cancer 86, no. 2 (2000): 169-173.
15. Ye, Lisa. “Alcohol and the Asian flush reaction.” Studies by Undergraduate Researchers at Guelph 2, no. 2 (2009): 34-39.
16. Chao, Ann, Michael J. Thun, Eric J. Jacobs, S. Jane Henley, Carmen Rodriguez, and Eugenia E. Calle. “Cigarette smoking and colorectal cancer mortality in the cancer prevention study II.” Journal of the National Cancer Institute 92, no. 23 (2000): 1888-1896.
17. Alcohol and Cancer Risk. National Cancer Institute
18. Hannan, Lindsay M., Eric J. Jacobs, and Michael J. Thun. “The association between cigarette smoking and risk of colorectal cancer in a large prospective cohort from the United States.” Cancer Epidemiology Biomarkers & Prevention 18, no. 12 (2009): 3362-3367.
19. 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.
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).
CureJoy Editorial

The CureJoy Editorial team digs up credible information from multiple sources, both academic and experiential, to stitch a holistic health perspective on topics that pique our readers' interest.

CureJoy Editorial

The CureJoy Editorial team digs up credible information from multiple sources, both academic and experiential, to stitch a holistic health perspective on topics that pique our readers' interest.