The Cancer it is one of the leading causes of illness and death in developed countries. In 2018, more than 18 million people around the world were affected by a tumor, a figure that will climb to 29.5 million in 2040. In Spain, more than 277,000 people were diagnosed with cancer in 2019. These data justify the interest in finding effective preventive strategies.
One of the best allies is the physical activity, and this has been shown by different studies. The patient information portal Cancer.net (from the American Society of Medical Oncology) states that physical activity is associated with a lower risk to develop, among others, a tumor of colon and breast. The question is what and how much Exercise must be done to get that benefit. Also, do all cancers they respond in the same way to physical activity?
These unknowns are those that an international team of researchers from some of the most prestigious institutions, such as the national institutes of the Cancer and Aging from the United States; the Institute Karolinska (Sweden) or the University of Melbourne (Australia). To do this, they examined the results of more than 750,000 people, followed by more than 10 years, included in 5 American, 3 European and 1 Australian cohorts corresponding to different studies
The main thing is to know what and how much physical activity to do to reduce the risk of cancer
Knowing the answers is very important for, the authors justify, establishing a recommendations of physical activity during leisure time (that is, it does not correspond to sports training) aimed at reducing the risk of developing cancer.
The researchers, who have published their work in the ‘Journal of Clinical Oncology’, focused on 15 types of cancer and found that in seven of them, reducing the risk associated with exercise it was particularly important (decreases from 6% to 27%). The best results were obtained for tumors of colon (decrease between 8% and 14%); mama (6% al 10%), endometrium (10%-18%), kidney (11%-17%), myeloma (14%-19%), liver (18% -27%) and linfoma no Hodgkin (11%-18%).
Minimum dose of activity
The mean cut-off exercise ‘dose’ was 2.5 hours per week of moderate intensity physical activity (for example, walking briskly), which is the minimum recommended by the experts (the average value of the people studied was slightly higher). From that cut figure, the scientists found that higher levels of activity were associated with a lower risk of breast, colon, endometrial, esophagus, and head and neck cancer. In contrast, more activity did not translate into a lower risk of kidney, gastric and liver cancer.
More intensity activity resulted in a lower risk of cancer of the colon in men (in women the relationship was not as strong) and Hodgkin lymphoma in women,
This work shows that the dose-response relationship is patent only in some types of cancer while in others, such as kidney or liver, exercising more than the recommended minimum does not achieve greater protection.
The variation in response to physical activity of the different tumors is also relevant, which, according to the scientists, may reflect important differences in the biological mechanisms underlying causes for various types of cancer. For example, “the main mechanisms proposed to explain the associations with the breast cancer are the circulating factors –sex steroid hormones, insulin, inflammatory biomarkers– which may have less impact on tumorigenesis in response to exercise “.
Miguel Ángel Seguí, of the working group of exercise and cancer of the Spanish Society of Medical Oncology (SEOM), confirms the variety of mechanisms that underlie the relationship between cancer and physical activity, but attaches special relevance to impact of obesity and, precisely, “it is the tumors most linked to obesity -endometrium, breast, colon, etc.- that register a more relevant reduction in risk”.
At liver, exercise has a direct effect on glucose, glycogen, and lipid metabolism and may lower the risk or reverse liver disease non-alcoholic fatty, an emerging risk factor for liver cancer.
Without fear of ‘overdose’
Alexander Lucia, researcher of the European University, agrees with Seguí that the benefit of physical activity on cancer is due to different reasons and admits that “there is a world to discover in this field.” After this clarification he describes: “Exercise makes the immune system against cancer. The cells that best respond to exercise are the ‘natural killer’ (a type of lymphocytes), which under the effects of physical activity target and infiltrate tumors. “At the same time, during exercise,” the muscles release the blood mioquinas, substances that have a certain antitumor effect“.
But the benefits of physical activity they do not manifest immediately, but rather after a few hours, when those myokines have been released and it has also been released adrenalin, which has an antitumor effect on breast cancer.
Regarding the risk of cancer and physical activity, this researcher defends the the more the better, and in the event that this is not the case -as the article in the ‘Journal of Clinical Oncology’ suggests-, “exercise does not carry no harm. A drug, in excess, can be harmful but a excessive physical activity, the worst thing you can have is that it is not more beneficial. ”
“What is bad for the body is the chronic stress associated with not doing any exercise, and repetition of acute episodes of stress with exercise is the most healthy because it leads the body to adapt, “insists Lucia.
Especially important is the anti-inflammatory effect of exercise, derived from myokines. “Many types of tumors – and other chronic diseases – are due to a state of chronic systemic inflammation, and along these lines, exercise is one of the main anti-inflammatory drugs that exist “.
Alejandro Lucía, who is professor of Exercise Physiology, says that “live without exercising it is living against our biology. ”
The expert reiterates that at least you have to do 2.5 hours a week of moderate activity, but “going up little by little is very positive.”
Walk at a good pace, put aside the elevator or escalator These are simple tips to move more and ward off cancer risk. Lucia has no doubt that “physical activity is a lifestyle.”
A meta-analysis carried out by Alejandro Lucía’s team, and published in the magazine ‘Mayo Clinic Proceedings’, found that elite athletes have 40% less risk death from cancer. “This supports the dose-response effect of physical activity against cancer.”
Seguí highlights that “this is the last work of many that confirm the positive relationship between physical activity and cancer”, and although share with the study authors the idea that from a level of physical activity you don’t get a ‘plus’ of benefit in less risk of developing cancer, it does emphasize that the important thing for this purpose is “the cumulative activity dose throughout life”.
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