You’ve heard of left- versus right-side brain. But what about left- and right-side colon? When it comes to cancer, there’s a big difference between these 2 sides.

Depending on your race, one side ages faster than the other side of your colon. What’s more, the rectum ages faster among white Americans. This comes from groundbreaking UVA Health colorectal cancer research. It helps shed light on an alarming trend — rising colorectal cancer rates among people in their 30s, 40s, and early 50s.

Here are 2 big reasons you need to know about this research. It helps us understand why:

1. Black Americans are at greater risk of dying from colorectal cancer. (This cancer killed beloved Black Panther star Chadwick Boseman at only 43.) 
2. More younger people, both Black and white, are developing cancer in the colon and the rectum.

Alarming Colon Cancer Rates in Young

Colorectal cancer (CRC) includes cancers in the colon and rectum — both are part of our digestive system.

Alarming increases in colon cancer rates in younger people is why we recommend that colorectal cancer screening begin at age 45. And doctors now recommend getting a colonoscopy even younger if you have symptoms such as blood in the stool.

Cynthia Yoshida, MD

Experts are concerned about what they call early-onset colorectal cancer. Since 1995, CRC in people under age 55 has nearly doubled. That means 1 in 5 new cases of colorectal cancer occurs in those under age 55.

And new colon cancer cases are rising 2% each year in this younger group. This comes from the American Cancer Society (ACS).

“The rate of increase in CRC in young people is alarming,” says colon health expert Cynthia Yoshida, MD. "At UVA Health, we’ve recently seen more cases of CRC in patients age 30s-40s, particularly left-sided colon cancer and rectal cancer.”

Targeted Colorectal Cancer Research

That’s also why UVA Health experts are doing targeted colorectal cancer research. They want to better understand the causes behind rising colon cancer rates among young people — and find ways to prevent it.

They do this with research through the Cancer Prevention and Population Health program at UVA Cancer Center. UVA has Virginia's only comprehensive cancer center designated by the National Cancer Institute.

Cancer researcher and family physician Li Li, MD, PhD, leads this program.

He also conducts his own colon cancer research. He and his research team have uncovered some fascinating things about how the colon and rectum age differently between Black and white Americans.

Here’s what you need to know.

More Dangerous Right-Side Colon Cancers in Black People

Americans with African ancestry tend to have more right-sided colon cancers.

“Right-sided colon cancer is more aggressive and has worse outcomes,” Li says.

Li’s research shows that for Blacks, the right-side colon was about 1.5 years older than the left side in the same person.

This is important to know, especially since the Black community has the highest colon cancer rates in the U.S. African Americans are about 20% more likely to get colorectal cancer and about 40% more likely to die from it than most other groups, says the American Cancer Society.

The reasons for the differences are complex. But they largely reflect differences in risk factors and in healthcare access. Both are related to socioeconomic status, says the ACS.

Rectum & Left-Side Colon Ages Faster in White People

For Americans with European ancestors, the UVA Health researchers found that the left side of the colon was about 1.9 years older than the right.

Not surprisingly then, white Americans more often develop the disease on the colon’s left side.

In another study, the researchers found that the rectums of European Americans age faster — by about 2.88 years — than that of African Americans. 

“This is consistent with the picture of more rectal cancers in European Americans and in younger adults,” Li says.

He adds, “We’ve come to realize that left- and right-sided colorectal cancers are two very different diseases, even though they are both colon cancers.”

Close Look at Colon & Rectum Biological Age

How did the researchers uncover aging and racial differences in the rectum and colon?

The researchers took tissue samples from inside the rectum and from inside both sides of the colon. These samples came from more than 100 people who didn’t have colorectal cancer.

The researchers then looked at DNA changes that come with age.

“We hope that knowing the differences in the biological aging of the rectum, along with the side-specific biological aging of the colon, will help guide the development of personalized prevention and intervention strategies,” Li says.