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Colorectal Cancer: Understanding Risks, Screening Guidelines and Lifestyle Recommendations

Published March 14, 2024

Any cancer that starts in the colon or rectum is considered colorectal cancer. According to the National Cancer Institute, in 2023 there were an estimated 153,020 new colorectal cancer cases in the United States and 52,550 deaths from the disease. Previously, improved survival rates were attributed in part to increased screening, changes in risk factors and better treatment options. However, during the COVID-19 pandemic, medical procedures that were considered nonessential were put on hold, prompting people to delay cancer screening and potentially its diagnosis. Colorectal cancer is currently the fourth leading cause of cancer and the second highest cancer-related cause of death in the U.S., based on 2023 estimates.

Colorectal cancer is more common in men than women, with incidence rates of 42.1% and 32.0%, respectively, from 2016 to 2020. The median age at diagnosis is 66. Although, the majority of diagnoses occur after the age of 50, a trend has been noted in the increased incidence of colorectal cancer in Americans under the age of 50, according to estimates from 2000 to 2019.

Higher incidence and death from colorectal cancer has been identified in Black individuals compared to other races, and there is a higher risk of death for American Indians and Alaska Natives. Racial and ethnic disparities in colorectal cancer are complex but attributable in part to barriers these individuals face in accessing health care.

Guidelines and screening

Several organizations have updated their screening guidelines due to the increased incidence of diagnoses among young adults. In May 2018, the American Cancer Society lowered the age of screening to 45 for people at average risk, meaning those who have no personal or family history of colorectal cancer or certain polyps; no personal history of inflammatory bowel disease; no confirmed or suspected hereditary syndromes that increase risk for colorectal cancer; and no personal history of radiation treatment to the abdomen or pelvis for prior cancer.

The ACS recommends individuals “in good health” and with a life expectancy of more than 10 years receive continued screening through age 75. For adults ages 76 to 85, screening should be assessed on an individual basis, considering personal preference, medical history and life expectancy. For those older than 85, screening is not recommended.

In May 2021, the United States Preventive Services Task Force updated its recommendation to offer screening at an earlier age of 45 (instead of 50) for those who are at average risk for colorectal cancer and continuing until the age of 75. Clinical Practice Guidelines released in November 2021 by the U.S. Multi-Society Task Force on Colorectal Cancer — which is comprised of experts representing the American Gastroenterological Association, the American College of Gastroenterology, and the American Society for Gastrointestinal Endoscopy — offered the same recommendation of earlier screening for adults who are deemed average-risk from age 45 to 75.

All people at high risk of colorectal cancer should discuss screening and recommended options with their physicians.

Screening involves one or more tests or procedures, depending on a person’s medical history, risk factors and preferences. There are three main types of visual exam: colonoscopy, which is considered to be the gold standard and typically is performed every 10 years for individuals who are not at increased risk; CT colonography, or virtual colonoscopy, which is performed every five years; and flexible sigmoidoscopy, which is performed every five years — or every 10 years if a stool test, called fecal immunochemical test (FIT), is performed annually. In addition to FIT, two other stool-based tests may be used to check for blood in the stool: guaiac-based fecal occult blood test, which is performed yearly; and the FIT-DNA test, which is performed every three years.

Identifying symptoms

Early-stage colorectal cancer often is asymptomatic. Colorectal cancer symptoms may include gas, bloating, changes in bowel habits, constipation, diarrhea, blood in stool or dark stools, iron deficiency anemia, weakness, fatigue and unexplained weight loss. Each of these symptoms may be attributed to many causes besides cancer, such as irritable bowel syndrome and stress. Any of these symptoms warrants a visit to the doctor.

Unfortunately, many people, especially younger adults, don’t seek medical attention right away, and when they do, misdiagnosis is common. According to a retrospective cohort study conducted in 2017, which included nearly 500,000 adults in the U.S., adults younger than 55 are 58% more likely to be diagnosed with late-stage colorectal cancer than older people. The study authors attributed this to delaying medical attention, in some cases for years, and “because cancer is typically not on the radar of young adults or their providers.”An international survey conducted in 2019, which included 885 patients and survivors with young-onset colorectal cancer, reflected that 62% waited at least three months before seeing a doctor regarding their symptoms and 75% saw at least two physicians before receiving the correct diagnosis. Eighty-one percent of those surveyed reported experiencing three symptoms prior to diagnosis. According to the MSTF, rectal bleeding, abdominal pain and changes in bowel habits were most often identified preceding a colorectal cancer diagnosis in younger adults.

Healthy lifestyle habits and risk reduction

While no cancer is 100% preventable, attention to diet and other lifestyle factors can help reduce risk. Specific to colorectal cancer, research suggests:

  • Limit red meat and avoid processed meat. Eating more than 18 ounces per week of red meat (including beef, pork and lamb) has been associated with a higher risk for cancer. The American Institute for Cancer Research recommends avoiding processed meats (those that have been preserved by smoking, salting, curing or adding other preservatives, including sliced turkey and bologna deli meats, bacon, ham and hot dogs). RDNs can encourage eating tofu, tempeh, beans, nuts, seeds and other plant-based protein sources to replace any or all meats.
  • Eat fiber-rich foods. According to the World Cancer Research Fund International, there is evidence that dietary patterns that include high amounts of fiber-rich foods, including vegetables, fruits, whole grains and legumes, is associated with a lower risk of colorectal cancer.
  • Limit alcoholic drinks. Evidence shows an increased risk for colorectal cancer with moderate to heavy alcohol consumption. One meta-analysis showed a 20% higher risk for colon cancer among people who had two to three drinks per day and a 50% higher risk with four or more drinks per day, compared with occasional or no alcohol use. One drink is about 5 ounces of wine, 12 ounces of beer or 1.5 ounces of distilled liquor. RDNs can counsel patients and clients on minimizing alcohol appropriately.
  • Don’t smoke cigarettes or use other tobacco products. In a large prospective study, incidence of colorectal cancer was about 30% higher in current and former smokers compared with lifelong nonsmokers. Colorectal cancer risk decreases over time after smoking cessation.
  • Achieve and maintain a healthy body weight. Excess body fat is associated with a higher risk for colorectal and other cancers. While overweight and obesity are multifactorial and not the result of diet alone, RDNs can counsel people on balanced, sustainable, calorie-appropriate nutrition as one way to promote a healthy weight and overall wellness.
  • Be physically active. Regular physical activity, including structured exercise and recreational activity, are associated with a lower risk for many types of cancer, including colorectal cancer. Given the well-known physical and mental health benefits of regular physical activity, RDNs can routinely promote this lifestyle practice.

Nutrition during and after treatment

Treatment for colorectal cancer may include surgery, chemotherapy, targeted therapy, radiation and immunotherapy.

Depending on the tumor site, surgery can involve the removal of any part of the colon and rectum. Nutrition-related complications may include short bowel syndrome, malabsorption, dehydration, adhesions and intestinal obstruction. Depending on symptoms and oral tolerance, it may be helpful for patients to eat small frequent meals; drink fluid between meals rather than with meals; minimize gas-producing foods and high-fiber foods; and limit the amount of high-fat foods and added sugars they eat. RDNs can help patients get adequate calories and protein to minimize the loss of lean body tissue and enough fluids to avoid dehydration.

Chemotherapy may be given before or after surgery and often involves a combination of medications. Side effects that may affect nutrition include decreased appetite, nausea, vomiting, diarrhea, constipation, abdominal pain, mouth sores or mucositis, changes in taste, difficulty swallowing, a suppressed immune system and fatigue. Diet modifications can be used in addition to medications for symptom management; for example, a tailored diet for diarrhea along with antidiarrheal drugs. Some side effects of radiation treatment to the abdominal area may be similar to those that arise during chemotherapy.

If a patient is experiencing nausea, RDNs can encourage small amounts of food and drinks at a time, drinking hot or iced ginger tea and avoiding greasy, fatty and fried foods as well as strong food odors. Some people feel best eating cool, moist foods such as yogurt, watermelon, applesauce or smoothies; others may find relief with dry, bland foods such as soda crackers or plain toast.

To manage diarrhea, patients should minimize very high-fiber foods such as wheat bran, as well as spicy foods, caffeine, fruit juices and foods with added sugars or sugar alcohols. In some cases, electrolyte-enhanced drinks may be useful for hydration and repletion. Patients can eat plain toast or pasta, bananas, white rice and unseasoned cooked fish, eggs or chicken. Small portions of cooked vegetables and fruits may be better tolerated than raw.

Some patients have a general loss of appetite. RDNs can discuss having small amounts of food and drink at a time, homemade or commercially prepared smoothies and shakes, “breakfast for dinner” foods and easy-to-eat foods such as individual yogurt cups, granola bars or packets of nuts.

For patients experiencing fatigue, RDNs can similarly encourage easy-to-eat or prepared foods, shakes or smoothies, and small frequent meals and snacks. Additionally, patients may feel better eating more food earlier in the day and less in the evening, and should limit or avoid alcohol, excess caffeine and foods or beverages high in added sugars.

If a patient has mouth sores, dry mouth or difficulty swallowing, RDNs can encourage moist foods, soups, smoothies or shakes, blended or pureed foods, cool or room temperature foods, drinking through a straw to avoid irritating sores, avoiding alcoholic drinks and avoiding dry, crusty, spicy or highly acidic foods.

Maintaining good oral hygiene is important both during and after treatment. Certain therapies increase the likelihood of tooth decay, cause dry mouth and weaken oral health, with effects that persist even after active treatment is completed. RDNs should encourage patients and clients to brush their teeth, rinse their mouths, stay hydrated, avoid alcohol-based dental products, minimize added sugars and sweets, avoid chewing gum with sugar and receive regular professional dental care.


This article originally appeared in Food & Nutrition Magazine®, published by the Academy of Nutrition and Dietetics.



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