October 2021 Issue

Cancer Nutrition: Early-Onset Colorectal Cancer
By Karen Collins, MS, RDN, CDN, FAND
Today’s Dietitian
Vol. 23, No. 8, P. 12

Dietitians Need to Talk Lifestyle Changes With Clients

Early-onset colorectal cancer is showing a worrisome increase at a time when overall US colorectal cancer incidence is declining. Evidence suggests early-onset colorectal cancer is just as strongly associated with diet, obesity, and sedentary lifestyle as when this cancer occurs later in life. This trend is a call to action for dietitians to step up educational efforts for adults aged 50 and under, many of whom consider themselves too young to worry about cancer.

Shifting Cancer Statistics
Colorectal cancer, the third most common cancer in both men and women, has been one of the “good news” stories. For more than a decade, age-adjusted rates of new cases and mortality rates have been falling approximately 2% per year.1 This is generally attributed to decreased smoking-related risk and increased screening.

However, these overall trends in colorectal cancer mask trends in young adults, among whom rates have been climbing since the mid-1980s.1,2 Yin Cao, MPH, ScD, is a cancer epidemiologist and associate professor of surgery at Washington University School of Medicine in St. Louis, and has been studying early-onset colorectal cancer extensively. “We have observed a birth cohort effect for early-onset colorectal cancer,” Cao says. “Elevated risk is observed among individuals born after 1950, and this birth cohort [this demographic group] has carried the elevated risk as they age.”

The majority of colorectal cancer still occurs in adults aged 50 and older, but trends in young adults are concerning. Reports projected 12% of cases in 2020 to be diagnosed in individuals younger than age 50.1

Research on Colorectal Cancer Risk
Nonmodifiable colorectal cancer risk factors include demographics, family history and genetic traits, and certain medical conditions.

Demographic data show colorectal cancer incidence and mortality highest in non-Hispanic Blacks and lowest in Asians/Pacific Islanders. According to the American Cancer Society, racial/ethnic disparities and low socioeconomic status are intertwined in links with colorectal cancer risk, as both can reflect prevalence of risk factors such as smoking and obesity and limited access to screening.1

Family history and hereditary mutations may be present in about 30% of people with early-onset colorectal cancer. A genetic predisposition occurs in less than 5% of colorectal cancer overall.3,4 But about 16% to 22% of people with early-onset colorectal cancer have mutations in genes such as tumor-suppressor genes.2,4 Among these, Lynch syndrome is the most common in early-onset colorectal cancer. Family history of colorectal cancer or advanced colorectal adenomas, especially in a first-degree relative, even without a recognized genetic syndrome, also significantly increases risk of overall colorectal cancer and early-onset colorectal cancer.2-4

Personal medical history of colorectal cancer, high-risk adenomas, or ovarian cancer increases risk of colorectal cancer. Chronic inflammatory bowel disease (ulcerative colitis or Crohn’s disease) and type 2 diabetes also signal increased risk.1,3

However, modifiable risk factors account for more than one-half of US colorectal cancer.1 Primary modifiable risk factors for both overall and early-onset colorectal cancer include excess body fat, physical inactivity, long-term smoking, excess alcohol consumption, and an unhealthful diet.

Growing research indicates the importance of the intestinal microbiota.2,5 People with colorectal cancer tend to have a greater proportion of bacteria that promote inflammation in the gut or produce carcinogenic metabolites and a smaller proportion of bacteria that produce butyrate, a short-chain fatty acid that protects colorectal cells.5

Close-Up on Diet
A Western diet was linked with a 67% increase in risk of early-onset high-risk adenomas in the Nurses’ Health Study II prospective cohort study.6 This dietary pattern, which is high in red and processed meats and refined grains, also has been linked with increased risk of overall colorectal cancer. Limited evidence suggests it may increase risk of distal colon and rectal cancers, the types that predominate in early-onset colorectal cancer.2,6

High intake of red meats, and especially processed meats, are strongly linked with overall colorectal cancer risk.7 Risk likely involves effects on the gut microbiota, promoting growth of bacteria that produce the proinflammatory compound hydrogen sulfide. It also may stem from red meat’s higher content of heme iron, which can increase free radicals that damage DNA and promote the formation of nitroso compounds. Processed meats can increase exposure to compounds such as the polycyclic aromatic hydrocarbons in smoked meats and nitroso compounds created when nitrites combine with a component of meat protein.

Excess alcohol consistently increases colorectal cancer risk with consumption of 30 g ethanol or more per day.1,3,7 That’s the equivalent of two or more standard alcoholic drinks, and risk is consistent regardless of whether consumption is from wine, beer, or distilled spirits. Alcohol is metabolized to acetaldehyde, a carcinogen that can damage colorectal cells. Risk also may come from an alcohol-related increase in oxidative stress and to alcohol’s ability to serve as a solvent, facilitating penetration of carcinogens into colorectal cells.7

Sugar-sweetened beverages (SSBs) have long been linked to cancer risk through promotion of weight gain and excess body weight when consumed frequently.8 “We’ve found a statistically significant association for women who consume two or more servings [equivalent to 16 oz or more] per day of sugar-sweetened beverages, even after adjusting for body mass index and other risk factors,” Cao says. Occasional consumption wasn’t linked with greater risk.9 “But compared with women consuming less than 8 oz weekly, those who consumed 16 oz or more daily during adulthood were more than twice as likely to develop early-onset colorectal cancer. And this level of consumption during adolescence was associated with even greater increase in risk.”

A high-quality, high-fiber diet, however, is likely to reduce risk. American Institute for Cancer Research analysis found strong evidence linking high-fiber diets and greater whole grain consumption with lower risk of overall colorectal cancer.7 Different types of dietary fiber can contribute to lower colorectal cancer through direct protection of colorectal cells, as well as support for protective, butyrate-producing bacteria in the gut microbiome.7,10

In the study of early-onset colorectal adenomas, Cao and colleagues found a consistent association between higher-quality diet and lower risk, regardless of whether diet quality was defined based on criteria for a DASH diet, Mediterranean diet, or adherence with Dietary Guidelines for Americans (using the Alternative Healthy Eating Index-2010).6 Higher scores for these patterns together suggest less incidence of high-risk adenoma among women whose diets were high in vegetables, fruits, whole grains, legumes, and nuts; contained more unsaturated fats and less saturated fat; and limited red and processed meats and SSBs.

“The consistency of these findings reinforces our message that maintaining a healthful diet is important in lowering risk of high-risk adenoma in younger adults,” Cao emphasizes.

Other potential protectors need more study in early-onset colorectal cancer. Moderate consumption of dairy products and calcium (with calcium intake of 700 to 1,000 mg per day) show strong links in reducing overall adenoma and colorectal cancer risk, possibly reflecting calcium’s ability to decrease cell proliferation and bind unconjugated bile acids. Limited evidence suggests that vitamin D, also supplied in dairy products, may reduce risk of overall colorectal cancer.1,7 However, it’s difficult to separate the influence of vitamin D from other risk-related factors.1,11 Besides the cross-over with calcium in dairy products, serum vitamin D often is higher in people who are physically active (because they tend to spend more time outdoors) and lower in people with obesity (as vitamin D sequesters in adipose tissue). Limited evidence suggests that fish consumption may be associated with lower risk of colorectal cancer.7 Current cancer-focused dietary recommendations don’t include any of these dietary components, pending further research.8,12

Obesity and Metabolic Syndrome
Just as diet may play a role in higher risk of colorectal cancer overall and early-onset colorectal cancer, research shows obesity and metabolic syndrome are additional factors. Excess body fat is a major risk factor consistently linked with greater incidence of and mortality from colorectal cancer.1,3,7 Excess adiposity can lead to elevated levels of insulin, which promotes cell growth and inhibits apoptosis (self-destruction of abnormal cells). Excess adiposity also can cause chronic inflammation, both systemically through inflammatory cytokines and potentially through the gut microbiome.2,7

Data are more limited regarding early-onset colorectal cancer but suggest that higher BMI increases risk, at least among women.1,2 In the Nurses’ Health Study II, each five-unit increase in BMI is associated with a 20% rise in risk of early-onset colorectal cancer, a greater increase than analysis shows for colorectal cancer overall. 7,13 “BMI at age 18 and BMI change since 18 are both associated with increased risk of early-onset colorectal cancer,” Cao says. Excess body fat as a factor in early-onset colorectal cancer is consistent with the generational increase in early-onset colorectal cancer occurring in the same birth cohort that has continually trended toward higher BMIs.2

Excess adiposity, particularly visceral fat, likely is tied to the association of metabolic syndrome with increased risk of colorectal cancer and early-onset colorectal cancer.1,14 “This relationship is actually a little stronger among younger adults compared with people who are aged 50 and above,” Cao adds. “While preliminary, this potentially indicates that metabolic dysregulation has a particularly stronger role in younger adults compared with older adults, which definitely merits additional research.”

Guidance for Reducing Colorectal Cancer Risk
Major US colorectal cancer screening recommendations now advise average-risk adults to begin regular screening at age 45 instead of 50.1,15 This allows for earlier colorectal cancer detection and treatment, and more opportunity to remove precancerous polyps before cancer develops.

“At least 70% to 80% of early-onset colorectal cancer occurs among people without family history,” Cao says. More research is needed with separate analyses of people with a hereditary syndrome or family history. “But based on current research, this increasing prevalence of early-onset colorectal cancer seems to be as strongly related to lifestyle as in overall colorectal cancer.”

Concern over rising rates of early-onset colorectal cancer may be the hook that generates interest from young adults, but dietitians can best promote overall health by addressing those concerns in the context of recommendations from the American Institute for Cancer Research and American Cancer Society that reduce overall cancer risk and risk of other chronic diseases.8,12 These recommendations are as follows:

• Keep weight within an individually healthy range and avoid weight gain in adult life.

• Get at least 150 to 300 minutes of moderate physical activity weekly (or the equivalent in vigorous activity), and limit sedentary habits. Physical activity is consistently linked with lower risk of colon cancer.1,3,7 And independent of exercise and obesity, moderate evidence links high amounts of sedentary time with greater risk of colon cancer and perhaps early-onset colorectal cancer specifically.16,17

• Create eating habits focused on whole grains, vegetables, fruits, and pulses (eg, dried beans and lentils). Aim to consume at least 30 g fiber per day, though protection comes from more than the fiber alone in the latter fiber-containing foods.8

• Limit red meat consumption to no more than 12 to 18 oz per week, and limit processed meats to only occasional intake.

• Limit SSBs, highly processed foods, and refined grain products. Frequent consumption increases risk of obesity-related cancers (including colorectal cancer). And emerging evidence discussed above suggests that SSBs may more directly increase risk of early-onset colorectal cancer.

• Avoid or limit alcoholic beverages of all types to no more than one drink per day for women, or at most two drinks per day for men. Limiting consumption reduces risk of several cancers, including colorectal cancer.

Researchers are studying other dietary components for potential to influence risk of colorectal cancer and early-onset colorectal cancer, specifically. The above choices highlight priorities based on today’s best evidence. Cao agrees: “I think the overall message is quite consistent that what we know for risk of colorectal cancer at older ages also applies for younger adults. It’s definitely important for our younger generation to adhere to a high-quality diet, maintain a healthy weight, be physically active, and reduce sedentary time as much as possible.”

— Karen Collins, MS, RDN, CDN, FAND, is nutrition advisor to the American Institute for Cancer Research and offers a membership program through her website that supports dietitians in cancer prevention, cardiovascular health, and cardio-oncology.


Education Resources

American Cancer Society
Colorectal Cancer Facts & Figures 2020–2022: cancer.org/research/cancer-facts-statistics/colorectal-cancer-facts-figures.html. Downloadable summary of types of colorectal cancer, statistics and trends, treatment options, and lifestyle choices related to colorectal cancer risk.

American Institute for Cancer Research/World Cancer Research Fund
Interactive Cancer Risk Matrix: wcrf.org/diet-and-cancer/interactive-cancer-risk-matrix. This is a clickable online database to check or use when talking about colorectal cancer and its associated risk factors.

AICR Media Library: aicr.org/resources/media-library. This link offers free downloadable infographics summarizing individual recommendations related to reducing colorectal cancer (and overall cancer) risk.

AICR New American Plate and Healthy10 Challenge: aicr.org/cancer-prevention/healthy-eating/new-american-plate. Here, dietitians will find messaging that pulls cancer prevention recommendations into one simple message about food portions and proportions to create eating habits that reduce cancer risk, and a free online program to help clients and patients make changes one step at a time.

— KC


1. American Cancer Society. Colorectal cancer facts & figures 2020-2022. https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/colorectal-cancer-facts-and-figures/colorectal-cancer-facts-and-figures-2020-2022.pdf. Published 2020.

2. Hofseth LJ, Hebert JR, Chanda A, et al. Early-onset colorectal cancer: initial clues and current views. Nat Rev Gastroenterol Hepatol. 2020;17(6):352-364.

3. Colorectal cancer prevention (PDQ) — health professional version. National Cancer Institute website. https://www.cancer.gov/types/colorectal/hp/colorectal-prevention-pdq. Updated June 29, 2021. Accessed July 13, 2021.

4. Mauri G, Sartore-Bianchi A, Russo AG, Marsoni S, Bardelli A, Siena S. Early-onset colorectal cancer in young individuals. Mol Oncol. 2019;13(2):109-131.

5. Reis SAD, da Conceicao LL, Peluzio M. Intestinal microbiota and colorectal cancer: changes in the intestinal microenvironment and their relation to the disease. J Med Microbiol. 2019;68(10):1391-1407.

6. Zheng X, Hur J, Nguyen LH, et al. Comprehensive assessment of diet quality and risk of precursors of early-onset colorectal cancer. J Natl Cancer Inst. 2021;113(5):543-552.

7. World Cancer Research Fund; American Institute for Cancer Research. Continuous Update Project: diet, nutrition, physical activity and colorectal cancer. https://www.wcrf.org/wp-content/uploads/2021/02/Colorectal-cancer-report.pdf. Updated 2018.

8. World Cancer Research Fund; American Institute for Cancer Research. Continuous Update Project: recommendations and public health and policy implications. https://www.wcrf.org/wp-content/uploads/2021/01/Recommendations.pdf. Published May 2018.

9. Hur J, Otegbeye E, Joh HK, et al. Sugar-sweetened beverage intake in adulthood and adolescence and risk of early-onset colorectal cancer among women [published online May 6, 2021]. Gut. doi: 10.1136/gutjnl-2020-323450.

10. O’Keefe SJ. Diet, microorganisms and their metabolites, and colon cancer. Nat Rev Gastroenterol Hepatol. 2016;13(12):691-706.

11. Vitamin D: fact sheet for health professionals. National Institutes of Health, Office of Dietary Supplements website. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/. Updated August 17, 2021. Accessed July 9, 2021.

12. Rock CL, Thomson C, Gansler T, et al. American Cancer Society guideline for diet and physical activity for cancer prevention. CA Cancer J Clin. 2020;70(4):245-271.

13. Liu PH, Wu K, Ng K, et al. Association of obesity with risk of early-onset colorectal cancer among women. JAMA Oncol. 2019;5(1):37-44.

14. Chen H, Zheng X, Zong X, et al. Metabolic syndrome, metabolic comorbid conditions and risk of early-onset colorectal cancer. Gut. 2021;70(6):1147-1154.

15. US Preventive Services Task Force; Davidson KW, Barry MJ, et al. Screening for colorectal cancer: US Preventive Services Task Force recommendation statement. JAMA. 2021;325(19):1965-1977.

16. Friedenreich CM, Ryder-Burbidge C, McNeil J. Physical activity, obesity and sedentary behavior in cancer etiology: epidemiologic evidence and biologic mechanisms. Mol Oncol. 2021;15(3):790-800.

17. Nguyen LH, Liu PH, Zheng X, et al. Sedentary behaviors, TV viewing time, and risk of young-onset colorectal cancer. JNCI Cancer Spectr. 2018;2(4):pky073.