EXERCISE LOWERS CANCER RISK
The data for this study utilized over 1 million Swedish men who were tested for their level of physical fitness by a military fitness test they were required to take starting at 18 years of age. The average age of the participants was 33 years old. Many years after the testing, the cancer rates of these subjects was determined, and data was compared for different levels of physical fitness which had been evaluated by the physical fitness tests performed years before. The physical fitness test involved riding a stationary bike, first at a low resistance level for five minutes, and then with an increase in resistance until the subject was too tired to continue.
For analysis of the data study subjects were divided into low, moderate and high levels of cardiorespiratory fitness. This was measured by testing the supply of oxygen to the muscles (V02) as the marker of one’s cardiovascular and respiratory system fitness. Their findings revealed that those who had the best level of fitness levels had an approximately 20% reduction in cancers of the head and neck and kidney cancer.
The risk of certain gastrointestinal cancers was lowered even more. The high-fitness group had 40% fewer cancers of the liver, the esophagus, the gallbladder and bile ducts. There was a 20% lower risk of colon and stomach cancers. Lung cancer was reduced by 42% , although it is felt that smoking habits influenced the greater cancer reduction that was found for this cancer.
Dr. Aron Onerup lead researcher says that as the participants’ level of physical fitness increased, the cancer incidence decreased, “but you don’t have to reach the top, elite athlete level to have a lower risk. An increase in fitness seems to be associated with a lower risk of developing most of these cancers.” He speculates that “from a public health perspective, you can see the kind of risk reductions that you might be able to achieve if you put public health efforts into facilitating physical activity and fitness in the population.”
A disturbing trend in the United States is a great increase in gastrointestinal cancer found among younger people. The American Cancer Society reported that now people under 55 account for 20% of all colorectal cancer cases and that is increasing. That number was only 11% in 1995.
According to a 2021 study, if the current trend continues it is felt that in several years, colorectal cancer will become the leading cause of cancer deaths in the U.S. among those aged 20 to 49.
Perhaps the largest study ever-March study analyzing data from more than 30 million subjects revealed that as little as 11 minutes of daily physical activity lowered the risk of death from a variety of cancers. The data also showed that it lowered the overall risk of death from any cause. This analysis was published in the British Journal of Sports Medicine. The data came from almost 200 different studies done around the world, looking at physical activity levels of people for a minimum of three years. They analyzed the data with respect to the development of over 20 different health conditions. They found that people who were moderately active-defined as physically active for 75 minutes per week- had lower risks of, heart disease, stroke and a variety of cancers compared to those who were physically inactive.
According to the National Cancer Institute there is strong evidence that the following lists of cancers are reduced by engaging regularly in physical activity.
- Bladder cancer: According to a 2014 analysis of 15 studies the risk of bladder cancer was 15% lower (5). Another pooled analysis of over 1 million people indicated that leisure-time physical activity was associated with a 13% reduced risk of bladder cancer by(6).
- Breast cancer: A 2016 meta-analysis of 38 studies showed that physically active women lowered their risk of breast cancer by 12–21% compared to those who were sedentary7. These findings are similar for both pre and postmenopausal women.(7, 8). It was also shown that those women who increased their physical activity after menopause also lower their risk of breast cancer (9, 10).
- Colon cancer: A 2016 meta-analysis of 126 studies, showed that those who were the most physically active lowered their colon cancer risk by 19% compared to those least physically active (11).
- Endometrial cancer: Obesity has been shown to be a strong risk factor for endometrial cancer (12–14). Although many analyses have shown that more physically active women have a lower endometrial cancer rate, it is felt that this association may be an indirect one, and related to the lowering of obesity which is also associated with greater physical activity.
- Esophageal cancer: A 2014 meta-analysis of 24 studies found a 21% lower risk of esophageal adenocarcinoma in those who were the most physically active compared to the least active women16.
- Kidney cancer: A 2013 meta-analysis of 19 showed a 12% lower risk for those who were the most active compared to those who were the least active (17). And a pooled analysis of over 1 million people showed that leisure-time physical activity reduced the risk by 23% (6).
- Stomach (gastric) cancer: A 2016 meta-analysis of 22 studies reported that those who were the most physically active had a 19% lower risk of stomach cancer compared to those who were the least active (18).
How might physical activity be linked to reduced risks of cancer?
Exercise has many biological effects on the body which help explain the association between increased physical activity and lower cancer risk:
- Preventing high blood levels of insulin, which has been linked to cancer development and progression (20) [breast, colon]
- Physical activity reduces underlying inflammation of the body.
- Physical activity improves immune system functioning
- By altering the metabolism of bile acids, physical activity decreases exposure of the gastrointestinal tract to a number of known carcinogens (21, 22).
- Enhancing gastrointestinal transit time (the time it takes for food to travel through the digestive system) decreases exposure of the gastrointestinal tract to carcinogens in foods.
- Exercise helps to lessen obesity, which is a risk factor for many cancers
Being sedentary increases cancer risk
The Department of Health and Human Services has published a Physical Activity Guidelines for Americans (1). It says that to get the health benefits of exercise adults should engage in 150 to 300 minutes of moderate-intensity aerobic act
- What about cancer survivors and exercise?
The American College of Sports Medicine International says (26) that exercise training is generally safe for cancer survivors and there are studies that indicate that it does improve survival rates for certain cancers.
- Breast cancer: A 2019 meta-analysis of studies of
breast cancer survivors showed that the most physically active had a 40% lower risk of death from breast cancer compared to those who were the least physically active (28).
- Colorectal cancer: A number of studies have been done which show that physical activity after a colorectal cancer diagnosis may reduce death from colorectal cancer by 30% .
- Prostate cancer: There have been a few studies that suggest that physical activity after a prostate cancer diagnosis may reduce death from prostate cancer by 33% .
There are also studies showing benefits to cancer survivors beyond reduction in death rates. Many studies have shown that there are a variety of benefits that accrue to people who exercise. These benefits are also show up when studying cancer survivors. Among the benefits are a reduction in anxiety, and depressive symptoms, there is less fatigue and an improved health-related quality of life and physical functioning reported.
In summary, the beneficial effects of exercise on the body have been shown so consistently that it can be confidently recommended to people of all ages, both sexes, and among all racial and ethnic groups, as a beneficial activity for their overall health and well being.