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Colon cancer is the second-deadliest form of cancer after lung cancer. If recent messages about colon cancer screening have left you a little confused, that's understandable. In August, the American College of Physicians (ACP) released updated guidance for colon cancer screening that differs from other major organizations, including recommendations from the American Cancer Society (ACS) and the US Preventive Services Task force (USPSTF).

So, what do you need to know?

How does the advice differ?

First, please note that this advice applies only to people at average risk without a family history of colon cancer. If you have family history, or if other health issues put you at higher-than-average risk for colorectal cancer, talk to your doctor about the best course of action for you.

The main point of disagreement relates to the age at which people should start getting screened. The new ACP guidance says 50, while the other two organizations recommend 45. That earlier age is endorsed by the U.S. Multisociety Task Force on Colorectal Cancer. It's also endorsed by many physicians, including Harvard Medical School professor Dr. Andrew T. Chan, a gastroenterologist and director of epidemiology at Massachusetts General Hospital Cancer Center, who helps explain key facts below.

Why do experts suggest starting screening earlier?

"We're facing an unexplained and alarming increase in the incidence of colon cancer in people younger than 50," says Dr. Chan.

Overall, deaths from colon cancer dropped by 2% per year from 2011 to 2020. But that's not the case among people younger than 50. In that age group, deaths from colon cancer rose between 0.5% and 3% during the same time period, according to statistics published in 2023.

The rising rates of colon cancer in younger people are occurring in all racial and ethnic groups, with the steepest rises seen among Alaskan Natives and Native Americans. Overall, Blacks and African Americans are more likely to get and die from colon cancer than whites, and early-onset cases are higher in Black individuals than whites.

Efforts to encourage colon cancer screening began in the mid-1990s. Today, about 60% of adults over 50 follow the advice to receive a colonoscopy (described below) on a regular basis. This track record, while not perfect, likely explains the decline in deaths from colon cancer in older adults.

"I think that promoting earlier screening will help stem the rise in early-onset cases, at least for those in their 40s. We've also seen that earlier colonoscopies may be associated with lowering incidence of colon cancer even later in life, "says Dr. Chan.

What are the different screening tests for colon cancer?

The two most widely used screening tests are a standard colonoscopy and various stool-based tests.

Colonoscopy. For this test, a gastroenterologist or surgeon snakes a long, flexible tube with a camera on the end through your rectum and beyond to inspect the entire length of your colon. Considered the gold-standard test, this procedure can detect precancerous polyps called adenomas, and allow for their removal.

The test requires taking laxatives and drinking lots of fluids beforehand to clean all the fecal material (stool) out of your colon. Serious complications, which include perforation or bleeding, are rare, occurring in about three in 1,000 procedures. If no polyps are found, a repeat colonoscopy isn't recommended for another 10 years. If you have polyps, or your risk or symptoms change, this interval will be shorter.

Stool tests. The more worrisome colon polyps (adenomas) often shed tiny amounts of blood and abnormal DNA into the stool. This can be detected from samples you collect yourself at home.

• Two tests, the fecal occult blood test (FOBT) and fecal immunochemical test (FIT), check for blood. They require small stool samples that you put on a card or in a tube that's then mailed to a lab. These tests should be done every year.
• A third option, the FIT-DNA test, checks for both blood and abnormal DNA; it's usually repeated every three years.

Additionally, the guidelines from the American College of Physicians suggest another option: flexible sigmoidoscopy, which inspects only the lower part of the colon, once every 10 years, combined with a fecal FIT testing every two years. However, doctors in the United States rarely order sigmoidoscopy today.

If flexible sigmoidoscopy or any of these stool tests show evidence of a problem, a colonoscopy is needed to check for adenomas or cancer.

Why might stool-based screening make sense for younger adults?

Colonoscopy isn't necessarily the best initial screening test for everyone, says Dr. Chan. That's especially true for younger people, mainly because it's time-consuming and inconvenient.

"Maybe you just can't find time in your schedule or are worried about having a colonoscopy," he says. If that's the case, a stool-based test — which is noninvasive and takes very little time — is an appropriate option.

"The worst option is not doing anything, because early detection and treatment can prevent deaths," he says.

About the Author

Julie Corliss, Executive Editor, Harvard Heart Letter

Julie Corliss is the executive editor of the Harvard Heart Letter. Before working at Harvard, she was a medical writer and editor at HealthNews, a consumer newsletter affiliated with The New England Journal of Medicine. She … See Full Bio View all posts by Julie Corliss

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

By the time boys are 8 or 10, they’re steeped in Marvel action heroes with bulging, oversized muscles and rock-hard abs. By adolescence, they’re deluged with social media streams of bulked-up male bodies.

The underlying messages about power and worth prompt many boys to worry and wonder about how to measure up. Sometimes, negative thoughts and concerns even interfere with daily life, a mental health issue known body dysmorphic disorder, or body dysmorphia. The most common form of this in boys is muscle dysmorphia.

What is muscle dysmorphia?

Muscle dysmorphia is marked by preoccupation with a muscular and lean physique. While the more extreme behaviors that define this disorder appear only in a small percentage of boys and young men, it may color the mindset of many more.

Nearly a quarter of boys and young men engage in some type of muscle-building behaviors. “About 60% of young boys in the United States mention changing their diet to become more muscular,” says Dr. Gabriela Vargas, director of the Young Men’s Health website at Boston Children’s Hospital. “While that may not meet the diagnostic criteria of muscle dysmorphia disorder, it’s impacting a lot of young men.”

“There’s a social norm that equates muscularity with masculinity,” Dr. Vargas adds. “Even Halloween costumes for 4- and 5-year-old boys now have padding for six-pack abs. There’s constant messaging that this is what their bodies should look like.”

Does body dysmorphic disorder differ in boys and girls?

Long believed to be the domain of girls, body dysmorphia can take the form of eating disorders such as anorexia or bulimia. Technically, muscle dysmorphia is not an eating disorder. But it is far more pervasive in males — and insidious.

“The common notion is that body dysmorphia just affects girls and isn’t a male issue,” Dr. Vargas says. “Because of that, these unhealthy behaviors in boys often go overlooked.”

What are the signs of body dysmorphia in boys?

Parents may have a tough time discerning whether their son is merely being a teen or veering into dangerous territory. Dr. Vargas advises parents to look for these red flags:

• Marked change in physical routines, such as going from working out once a day to spending hours working out every day.
• Following regimented workouts or meals, including limiting the foods they’re eating or concentrating heavily on high-protein options.
• Disrupting normal activities, such as spending time with friends, to work out instead.
• Obsessively taking photos of their muscles or abdomen to track “improvement.”
• Weighing himself multiple times a day.
• Dressing to highlight a more muscular physique, or wearing baggier clothes to hide their physique because they don’t think it’s good enough.

“Nearly everyone has been on a diet,” Dr. Vargas says. “The difference with this is persistence — they don’t just try it for a week and then decide it’s not for them. These boys are doing this for weeks to months, and they’re not flexible in changing their behaviors.”

What are the health dangers of muscle dysmorphia in boys?

Extreme behaviors can pose physical and mental health risks.

For example, unregulated protein powders and supplements boys turn to in hopes of quickly bulking up muscles may be adulterated with stimulants or even anabolic steroids. “With that comes an increased risk of stroke, heart palpitations, high blood pressure, and liver injury,” notes Dr. Vargas.

Some boys also attempt to gain muscle through a “bulk and cut” regimen, with periods of rapid weight gain followed by periods of extreme calorie limitation. This can affect long-term muscle and bone development and lead to irregular heartbeat and lower testosterone levels.

“Even in a best-case scenario, eating too much protein can lead to a lot of intestinal distress, such as diarrhea, or to kidney injury, since our kidneys are not meant to filter out excessive amounts of protein,” Dr. Vargas says.

The psychological fallout can also be dramatic. Depression and suicidal thoughts are more common in people who are malnourished, which may occur when boys drastically cut calories or neglect entire food groups. Additionally, as they try to achieve unrealistic ideals, they may constantly feel like they’re not good enough.

How can parents encourage a healthy body image in boys?

These tips can help:

• Gather for family meals. Schedules can be tricky. Yet considerable research shows physical and mental health benefits flow from sitting down together for meals, including a greater likelihood of children being an appropriate weight for their body type.
• Don’t comment on body shape or size. “It’s a lot easier said than done, but this means your own body, your child’s, or others in the community,” says Dr. Vargas.
• Frame nutrition and exercise as meaningful for health. When you talk with your son about what you eat or your exercise routine, don’t tie hoped-for results to body shape or size.
• Communicate openly. “If your son says he wants to exercise more or increase his protein intake, ask why — for his overall health, or a specific body ideal?”
• Don’t buy protein supplements. It’s harder for boys to obtain them when parents won’t allow them in the house. “One alternative is to talk with your son’s primary care doctor or a dietitian, who can be a great resource on how to get protein through regular foods,” Dr. Vargas says.

About the Author

Maureen Salamon, Executive Editor, Harvard Women's Health Watch

Maureen Salamon is executive editor of Harvard Women’s Health Watch. She began her career as a newspaper reporter and later covered health and medicine for a wide variety of websites, magazines, and hospitals. Her work has … See Full Bio View all posts by Maureen Salamon

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD