Men who get regular cardio exercise and have high fitness levels are less likely to develop colorectal cancer, a disease that increasingly has affected people at younger ages over the last few decades. That's according to new research from a large Swedish study that also found men with high levels of cardio are less likely to die of lung or prostate cancers.
Colorectal cancer is the second leading cause of cancer-related death in the U.S. It usually begins with growths on the inner lining of the colon or rectum. Common symptoms include changes in bowel habits that persist for more than several days, rectal bleeding, blood in the stool, abdominal cramping and fatigue.
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Some of the most common risk factors for colorectal cancer — obesity, Chron's disease, ulcerative colitis and diabetes — have been on the rise among millennials. This age group now has more than twice the risk of developing colorectal cancer compared to people born in 1950, and people under 55 are more likely to be diagnosed with late-stage disease than those who are older.
The trend of younger people developing colorectal cancer has led to revised screening guidelines in the U.S. Americans now are urged to get their first colonoscopies at 45 instead of 50. Though prevention efforts primarily have focused on a combination of physical activity and dietary choices, new research suggests that cardio fitness specifically plays a role in lowering risks.
Cardiorespiratory fitness refers to how well the circulatory and respiratory systems are able to supply oxygen to the body during physical activity. Exercises like running, cycling and swimming all improve cardio fitness by maintaining healthy weight, controlling blood pressure and boosting stamina and endurance.
The Swedish study looked at data on more than 178,000 men who had completed health assessments between 1982 and 2019. The men rode exercise bikes to test their cardio health as doctors measured their blood oxygen levels. These men were followed years later on Swedish health registries to determine who had developed various cancers and which health factors were linked to lower risks.
The more fit the men were based on their cardio tests, the less likely they were to develop or die from colorectal, prostate and lung cancer.
Men with moderate cardio fitness were 28% less likely to develop colorectal cancer than those with low cardio fitness. The group with the highest level of cardio fitness was 37% less likely to develop colorectal cancer than the the low fitness group.
When adjusted for smoking, the risk of death from lung cancer was 59% lower in men with high cardio fitness compared to those with low fitness. And among men who developed prostate cancer, those with moderate and high cardio fitness were 43% and 71% less likely to die from the disease, respectively, than those with low fitness.
"Current cancer prevention guidelines focus on physical activity, but these findings show that cardiorespiratory fitness is also very important for both reducing cancer risk and risk of death from common cancers in men," Elin Ekblom-Bak, one of the lead authors of the study, told U.S. News & World Report.
The research stands out because the men tracked in the study were given advanced tests of cardio fitness alongside other important measures such as height and weight. The study offered researchers various data points and consistent follow-up that often are lacking in investigations of this size. Detailed information about race was not included in the study; in the U.S., Black men and women are 20% more likely to get colorectal cancer and about 40% more likely to die from it than most other groups.
Although the study looked only at men, past research has shown that higher cardiorespiratory fitness also is linked to lower cancer rates and deaths among women.
Cardio fitness lowers inflammation and promotes better blood sugar levels. This reduces stress on the cellular systems that become more prone to cancer development as people age, which may help explain why fitter people are less at risk for many cancer types. The study expands on common recommendations of cardio exercise to maintain heart health.
The researchers noted that maintaining cardio fitness requires at least moderate intensity during exercise — enough exertion to feel quickened breathing.
"The increase in fitness is both related to the intensity and the amount of physical activity performed, but also to individual genetic factors," Ekblom-Bak said.