African Americans have higher colon cancer risk factors than any other race. Here's what you should know about colorectal cancer.
Colorectal cancer, which includes cancers of the rectum and colon, is the third most common cancer in the United States. It’s also one of the deadliest. Colon cancer is the second leading cause of cancer-related deaths among both men and women. In 2013, there were more than 136,000 cases of colon cancer diagnosed in the United States alone, as well as over 50,000 deaths due to the disease.
While there are many colon cancer risk factors, your race may play a role as well. In the United States, African Americans are more likely than any other racial group to develop colorectal cancer, or cancer of the gastrointestinal system that includes both the rectum and the colon.
Colon cancer risk factors for African Americans
The Centers for Disease Control and Prevention report that in 2013, 27.4 people out of every 100,000 developed colon cancer. However, among African Americans, that rose to 33.5 out of every 100,000. For Caucasian Americans, that number was only 27.4 out of 100,000, and for Asians and Pacific Islanders it was even lower at 19.3.
The American Cancer Society (ACS) warns that African Americans have the highest death rate and shortest survival rate for most cancers out of any racial group in the United States, including colon cancer survival rate. Much of this difference in mortality is caused by access to care, including the quality of screening and treatment.
However, multiple research teams have also looked for other causes of the connection between African Americans and colon cancer risk factors.
A study comparing colon and rectal cancers in Native American and African Americans found that not only was Native Americans’ risk of developing colorectal cancer much lower, the two groups had significantly different diets. This caused changes in their gastrointestinal bacteria, leading researchers to theorize that colon cancer risk was affected by the interaction between dietary and bacterial factors.
Diet is strongly linked to culture and socioeconomic class, both of which are also linked to race. This may account for why forms of colorectal cancer in African Americans are more common than for other races.
Reducing colon cancer risk factors
The links between forms of colorectal cancers and diet are good news. Because these cancers appear to be influenced by lifestyle as well as genetics, there is also evidence that lifestyle changes can reduce the risk of developing colon cancer.
Research comparing the risk of colorectal cancers in African Americans to that of rural South Africans examined the effect of switching the two groups’ diets. When the South African participants ate a typical low-fiber, high-fat, high animal protein Western diet, their risk for colon cancer rose. Their gut bacteria also changed to more closely resemble that of African Americans in the study.
The African American participants, by contrast, consumed more fiber and less fat, as well as limiting animal protein. Within two weeks, researchers found that gut bacteria linked to higher risk of colon cancer decreased for African Americans on the new diet, and that participants showed lower levels of the gut inflammation that can cause cellular mutations.
Both studies demonstrate the importance of diet, intestinal bacteria, and gut health in understanding the links between African Americans and colon cancer risk factors.
Rex Gaskins, PhD, a professor at the University of Illinois, has co-led research on why African Americans are more likely to develop forms of colorectal cancer. Gaskins noted that scientists are "beginning to connect the dots between these dietary factors and one's risk of developing colon cancer risk.... The microbes that inhabit the colon are part of the equation and should not be overlooked."
Symptoms of colon cancer
In its early stages, colon cancer often does not cause symptoms. The first sign that colon cancer is developing is usually the growth of tumors or precancerous polyps in the large intestine. Because the symptoms of colon cancer are not always obvious, the ACS recommends regular screening to look for signs of cancer before it develops, especially for high risk groups like African Americans.
Once the cancer progresses, symptoms can become very noticeable. These are primarily related to the gastrointestinal system and can include rectal bleeding, blood in stool, a change in bowel habits that lasts more than a few days, and persistent abdominal pain. Colon cancer can also cause fatigue or unexplained weight loss.
Many of these changes can indicate other gastrointestinal conditions, so it is important to speak with a healthcare professional if you experience anything that might be a symptom of colon cancer. Your doctor will be able to recommend any necessary testing or treatment, including screening for cancer.
April 17, 2018
Christopher Nystuen, MD, MBA