Why Is Colorectal Cancer Rising in Younger Adults?

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In recent decades, a concerning trend has emerged in colorectal cancer (CRC)—while overall incidence and mortality rates have decreased in older adults, the number of younger adults diagnosed with this disease has steadily risen. This phenomenon, often referred to as early-onset colorectal cancer (EOCRC), is puzzling researchers and clinicians alike. Understanding why this is happening, identifying key risk factors, and promoting preventative strategies are crucial steps toward reversing the trend.

For an in-depth look at gut health and how it influences overall wellness, read my article on The Brain-Gut Connection.

Historically, colorectal cancer was primarily considered a disease of older adults, with most cases occurring after the age of 50. However, data from recent studies show a significant rise in CRC cases among individuals under 50:

  • Increase in Incidence: Between 1994 and 2019, the incidence of CRC in adults under 50 increased by nearly 2% annually (American Cancer Society). In my own personal experience, I think the risk is increasing with each passing year. I used to discover a few every year several years ago, but now it appears that I see younger people with colorectal cancer several times a month. Also, as we have reduced the age for CRC screening to 45, I see younger people with polyps and many times incidental polyps in individuals in their 20’s and 30’s.
  • Higher Proportion of Rectal Cancer: Early-onset cases disproportionately affect the rectum compared to older adults, with rectal cancer comprising over 30% of EOCRC cases. Rectal bleeding, changes in the caliber of stool, rectal discomfort, unusual constipation should alert one to see advice from primary care physicians who will most likely refer you to a gastroenterologist.
  • More Advanced Stage at Diagnosis: Younger patients are often diagnosed at a later stage due to delayed recognition of symptoms and lower screening rates. Early screening is the key.

Key Risk Factors for Early-Onset CRC

The causes of early-onset CRC are multifactorial, involving a combination of genetic, environmental, and lifestyle factors.

1. Genetics and Family History

  • A family history of CRC or hereditary syndromes such as Lynch syndrome or Familial Adenomatous Polyposis (FAP) significantly increases the risk.
  • Genetic mutations in mismatch repair genes can predispose individuals to cancer at a younger age.
  • Approximately 20% of EOCRC cases have a hereditary component on the other had 80% don’t!

For those with a family history, early screening and genetic counseling are crucial. Learn more about the role of genetics in CRC.

2. Diet and Lifestyle

  • Diets high in red and processed meats, low in fiber, and rich in refined sugars are linked to a higher risk of CRC.
  • A sedentary lifestyle and lack of physical activity contribute to metabolic dysregulation, increasing inflammation and cancer risk.
  • Obesity: Excess visceral fat is a known risk factor for CRC due to its role in promoting chronic low-grade inflammation.

For practical dietary advice, visit my post on Gut-Healthy Foods.

Why Are Young Adults at Greater Risk Now?

The reasons for the rising incidence of CRC in younger populations are not fully understood, but several hypotheses have been proposed:

  • Delayed Diagnosis: Young adults often dismiss early symptoms, such as rectal bleeding, abdominal pain, and changes in bowel habits, attributing them to less serious conditions like hemorrhoids or irritable bowel syndrome (IBS).
  • Changes in Lifestyle and Diet: Over the past few decades, there has been a marked shift toward more sedentary lifestyles and diets high in processed foods and sugar.
  • Increased Inflammation: Obesity and poor diet contribute to systemic inflammation, which can promote carcinogenesis.
  • Gut Health Disruption: Altered gut microbiota, possibly linked to dietary changes, antibiotic overuse, and lack of dietary fiber, may also play a significant role.

Preventative Measures for Early-Onset CRC

1. Screening and Early Detection

  • Start Screening Early: The American Cancer Society now recommends starting CRC screening at age 45 for average-risk individuals. I worry about patients who get a colonoscopy at age 45 and had no polyps. Does it mean that patient doesn’t have a risk and therefore he/she should be back in 10 years or the risk is being underestimated and we are still recommending a 10 year follow-up? Whatever the risk is, does it increase the risk gradually over time or does it manifest itself sooner rather than later? If the risk is there is for younger population, why the risk has not manifested itself in the older population or will it rear it ugly face later in life? If one were to do a mental exercise, the only sure way to prevent colorectal cancer in every one is do colonoscopy every year, but it is neither practical or safe. Barring that approach, what can we do to mitigate one’s own risk? I will discuss that in my next article.
  • Know Your Family History: Individuals with a family history of CRC should begin screening 10 years earlier than the age at which their relative was diagnosed. Though this is an important factor, not having a family history of CRC is not an insurance policy.
  • Consider Genetic Counseling: For those with a strong family history or hereditary syndromes, genetic counseling can help assess risk.

2. Diet and Lifestyle Modifications

  • Increase Fiber Intake: High-fiber diets reduce the risk of CRC by promoting healthy bowel movements and feeding beneficial gut bacteria.
  • Limit Red and Processed Meats: Reducing intake of these foods can lower cancer risk.
  • Stay Active: Regular physical activity helps regulate metabolism and reduce inflammation.
  • Maintain a Healthy Weight: Reducing visceral fat through diet and exercise can significantly lower risk.
  • Consuming Cruciferous Vegetables: There is evidence that Broccoli, Kale, Cauliflower on regular basis may reduce risk for CRC.

Reducing Saturated Animal Fats.

  • Flax seed powder: This contains lignans which has been shown to reduce risk of several varieties of cancer.
  • Curcumin: Several studies have shown it’s effect both in lab models and human studies. Here is the link of one of articles published in Journal Apoptosis.

3. Promote Gut Health

  • Probiotics and Prebiotics: Consuming fermented foods like yogurt and prebiotic-rich foods like garlic can improve gut microbiome diversity.
  • Reduce Antibiotic Overuse: Only use antibiotics when necessary, as they can disrupt the gut microbiota.
  • Avoid Excessive Alcohol: Heavy alcohol consumption is a known risk factor for CRC.

References

  1. Siegel RL, et al. Colorectal cancer statistics, 2020. CA: A Cancer Journal for Clinicians. 2020;70(3):145-164. doi:10.3322/caac.21601.
  2. Wong SH, Yu J. Gut microbiota in colorectal cancer: mechanisms of action and clinical applications. Nature Reviews Gastroenterology & Hepatology. 2019;16(11):690-704. doi:10.1038/s41575-019-0209-8.
  3. Stoffel EM, et al. Hereditary colorectal cancer syndromes: Molecular genetics, genetic counseling, diagnosis, and management. Gastroenterology. 2018;154(2):324-335. doi:10.1053/j.gastro.2017.09.018.
  4. Murphy N, et al. Lifestyle and dietary environmental factors in colorectal cancer. Nature Reviews Clinical Oncology. 2019;16(10):605-619. doi:10.1038/s41571-019-0204-3.
  5. Agarwal B, Swaroop P, Protiva P, Raj SV, Shirin H, Holt PR. Cox-2 is needed but not sufficient for apoptosis induced by Cox-2 selective inhibitors in colon cancer cells. Apoptosis. 2003 Dec;8(6):649-54. doi: 10.1023/A:1026199929747. PMID: 14739610.

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