The study involved analyzing the effects of exercise on over 49,000 people, with their ages ranging between 40 and 70. They went through physician-referred treadmill exercise stress testing from 1991 and 2009. After the end of the stress testing, the researchers went on to observe the participants for a median of 7.7 years.
Over the course of the study, 388 participants developed lung cancer, of which 282 died from the disease. Meanwhile, 220 participants developed bowel tumors, of which 89 died.
The results showed that the participants who exercised the most had a 77 percent decreased risk of developing lung cancer and a 61 percent reduced risk of developing colorectal cancer.
Furthermore, the researchers found that for the participants that were diagnosed with lung and colorectal cancers, they had a 44 percent and 89 percent decreased risk of succumbing to the disease, respectively.
The researchers went on to note that their study may be the first of its kind to include such a large amount of participants, as well as the first to involve large numbers of women (46 percent) and have a diverse pool of patients – 64 percent were white, 29 percent were black, and one percent were Hispanic.
In understanding just why the risk of lung and colorectal cancers is reduced by exercise, the scientists noted that it may be due to the positive effects exercise has on the body, namely increased circulation and elimination of toxins from both of these areas. They said that being active significantly improves the health of the heart, lungs, and immune system.
Furthermore, with respect to the effects of exercise on the digestive system, physical activity has been shown to help move food through the digestive tract more efficiently. This helps keep food and other chemicals found in waste from staying too long within the body. Lastly, the researchers noted that being active helps lower inflammation, which stops cells from dividing often. Excessive and uncontrollable cell division raises the risk of tumors developing. (Related: Working out in the morning helps improve cognitive function throughout the day, say researchers.)
These findings add to the growing body of evidence showing the effects of natural remedies for preventing cancer. Exercising has been linked to lowering the risk of five other kinds of cancer, including endometrial, breast, and ovarian.
Several other studies have been conducted exploring the relationship between cardiorespiratory fitness and cancer risk. One such study, published in JAMA Oncology, found an inverse association between fitness and lung and colorectal cancer incidence in middle-aged men. Another study, conducted by the University of Eastern Finland, concluded that increasing the amount of exercise that middle-aged men went through helped protect them against lung cancer.
The above studies are just a couple of samples from the many publications illustrating the link between regular exercise and reduced cancer risk.
In 2019, lung and colorectal cancers are expected to be the cause of death for about 142,670 and 51,020 deaths in the U.S., respectively. This study is important in preventing those numbers from going up any further.
Dr. Catherine Handy Marshall, the lead researcher of the study, concluded that more research needs to be done to further investigate the link between fitness and cancer risk. “Future research is needed to determine whether this association is similar in the general population and to determine whether improving fitness can influence cancer and mortality rates.”