Cancer Prevention and Exercise

Chris Tse and Brent Kastelic

Cancer is a complex set of diseases.  To date there are over 200 different known cancers that can develop in all of our organs (1). The causes are more diverse than the types of cancers; it is an interplay between genetics and environment (sociological, environmental, nutrition, activity, etc…)  The genetic relationship plays a small role in all cancers, about %5-10, are linked back to mutated genes (2) so what we do to ourselves and what we are exposed to every day are significant to the potential development of these diseases.  Cancer is a result of a defect in normal cells that causes them to grow rapidly, and divide without the normal control mechanisms.  Cells normally regulate themselves: if a cell is old, or isn’t acting normally it kills itself; but in cancerous cells this programmed death is switched off.  In science we talk a lot about disease treatment; let’s face it, it is sexier to talk about a novel techniques or drug than it is to talk about lifestyle changes.  But think about the following relationship: over the past 100 years our society has become progressively less active, increasingly mentally stressed, adopted many poor eating habits, living in more polluted cities, and almost at the exact same time chronic diseases like cancer are on the rise; coincidence? I think not.  Following the old medical treatment model without creating a healthier lifestyle is likened to trying to plant a flower in a pool of toxic sludge.

Over the past 10 years there has been a progressive shift in momentum in research: integrating exercise and nutrition as part of the prevention, treatment, and recurrence plan for cancer.  Prevention studies have always been an area of opportunity that is missed partially because of the length of time of each study.  What we sometimes fail to realize in the non-science world is that, in research, studies are run by grants and funds that have deadlines as short as one year or as long as 5-10.  So researchers need to constantly apply and re-apply for grants.  That’s why the Alberta Cancer Foundation and events like Bust a Move are so integral to funding local research! (Oh and if you could help us raise some money by clicking the link here: http://bit.ly/1kQ6OMC that would be great!) So you can see the difficulty in running prolonged studies that are 10 – 20 years long.  In prevention studies the focus has been more on biomarkers, potential chemical indicators in our bodies, that have been found to be associated with the disease.

The more prevalent biomarkers used in cancer research and exercise are (3, 4, 5):

  • Inflammatory chemokines (chemical signals in the body)
  • Immunity
  • Hormones (estrogen, progesterone, and testosterone)
  • Insuline-like growth factors (chemicals and proteins associated in growth of most cells)
  • Free radicals (what anti-oxidants fight against)

Obesity is also an indicator too: over %25 of cancer cases worldwide are caused by obesity and sedentary lifestyles so the relationship is significant (6).

What we do know about exercise is that increasing exercise levels to 150 minutes of moderate to intense exercise a week can lead to the following changes in those biomarkers:

  1. Inflammatory Chemokines: chemicals that cause inflammation have been found to be associated with numerous chronic health conditions including cancer.  Exercise is thought to assist in reducing the amount of these chemokines circulating in the body; this can be accomplished by the workout itself and with the change in body composition (7).  Fat cells are constantly releasing chemicals that cause inflammation so reducing body fat can assist in reducing the possibility of getting cancer.
  2. Immunity: If a person exercises regularly it has been found to boost immune function.  Certain cancerous cells can be recognized by our immune cells and then subsequently killed.  It has been found however that too much exercise can suppress the immune system which reverses this effect (5).
  3. Hormones: exercise is associated with a decrease level of circulating estrogen and progesterone.  These two hormones encourage cell replication and, in higher amounts, have been found to be risk factors for cancer (8).  Exercise has also been found to increase sex hormone binding globulin levels which bind estrogen, progesterone, and androgens (male hormones) which could be it’s primary way of reducing the amount of hormones in blood (9).
  4. Insuline-Like Growth Factors: these factors are involved in cell reproduction.  People who have diabetes and some cancers have been found to have higher insuline levels which is a result of a decreased presence of insuline-like growth factors. Exercise increases the production of these factors reducing the amount of insuline circulating in the blood (3).
  5. Free Radicals: these chemicals have been found to damage lipids, proteins, and DNA causing cell death.  Muscle contraction during exercise have been found to increase the production of free radicals which allows the body to naturally produce more anti-oxidants to regulate cell growth.  The biggest issue with exercise is that too much exercise will actually cause non specific damage to the body because of an overproduction of free radicals in comparison to the availability of anti-oxidants (10).

Ultimately the conversation about exercise and cancer prevention should not be about the type of exercise but the intensity and the frequency.  If we treat exercise like any other drug we need to design a dose and type specific for each person: too much and exercise can cause excessive damage, too little and it will not achieve the desired preventative effect. It’s the three little bears all over again!  The relationship between obesity and cancer is quite relevant to many of the same biomarkers:  auto-immune diseases, frequent illness, diabetes mellitus, arthritis, mental health concerns can all be tied into poor nutrition and low exercise and are found to be important in the development of both diseases.  So maintenance of a healthy lifestyle, and weight reduction are crucial to the reduction of a web of heath conditions.

Click here for my previous blog on Exercise and Cancer. 

 

Literature Cited:

(1) http://www.cancerresearchuk.org/cancer-help/about-cancer/cancer-questions/how-many-different-types-of-cancer-are-there, accessed February 16, 2014.

(2) http://www.cancer.org/cancer/cancercauses/geneticsandcancer/heredity-and-cancer, accessed February 16, 2014.

(3) Westerlind, K. Physical Activity and Cancer Prevention – Mechanisms. Medicine and Science in Sports & Exercise: 2003; 03: 1834 – 1840.

(4) McTiernan, A. Intervention Studies in Exercise and Cancer Prevention. Medicine & Science in Sports & Exercise: 2003; 03: 1841 – 1845.

(5) Campbell, K., McTiernan, A. Exercise and Biomarkers for Cancer Prevention Studies. The Journal of Nutrition: 2007; 07: 161 – 169.

(6) Vainio H., Bianchini F., eds. Weight control and physical activity. Lyon: IARC Press; 2002

(7) Marcell T., McAuley, K.,  Traustadottir, T., Reaven P. Exercise training is not associated with improved levels of C-Reactive protein or adiponectin. Metabolism. 2003;54:533-541.

(8) Liang J., Shang, Y., Estrogen and Cancer. Annual Review of Physiology: 2013;75:225-240

(9) Friedenreich, C., et. al.,  Alberta Physical Activity and Breast Cancer Prevention Trial: Sex Hormone Changes in a Year-Long Exercise Intervention Among Postmenopausal Women. Journal of Clinical Oncology: 2010; 28:9:1458-1466

(10) Vina, J., & Gomez-Cabrera, M. FORUM ISSUE: “Free Radicals and Physical Exercise”: Free Radical Research, January 2014;48(1):1–2

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About Chris Tse

I’m a scientist turned owner of Blitz Conditioning, a Fitness Columnist at CBC Radio on Thursdays at 8:20 am, and owner of Tse Social Strategy. Follow me on Twitter or Read my full bio.

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