Cancer Prevention

On cancer prevention and exercise

Scientific research: protective effect of physical activity & training

Exercise the wonder drug

As shown in various studies (incl. the long-term Nurses' Health Studies I and II which in an effort to assess risk factors for cardiovascular disease and cancer followed more than 100,000 nurses over many years), regular physical exercise can have numerous health benefits. These range from strengthening a person's immune system, mental health and well-being and promoting/maintaining healthy bone density, all the way to helping to prevent depression, Type 2 diabetes, dementia and heart and cardiovascular disease, and even reducing the risk of surgery.

Last but not least, exercise & training show a protective effect on cancer incidence and risk as well as mortality after diagnosis. In fact, strong evidence points to exercise exerting a beneficial effect on the risk of developing certain types of cancer, particularly of the colon, breast and endometrium, and there is evidence for a protective effect against other cancers as well.

Physical activity has even been observed to improve quality of life and outcome for cancer patients undergoing conventional treatment.

Another possible reason why exercise helps in health and healing

In addition to exercise's positive influence on glycemic control (decreased glucose concentrations, with even simple passive stretching of the muscles helping to lower blood glucose levels — see www.ncbi.nlm.nih.gov/PubMed/21843832 — and sugar being known to feed cancer), recent research has shown that skeletal muscle actually acts as an endocrine organ.

During movement or contraction, these muscles release substances known as myokines (hormone-like semiochemicals). Research to date has ascertained myokenes to affect metabolism, type 2 diabetes, the cardiovascular system and the brain, and generally to act as mediators of systemic and local anti-inflammatory effects.

See for instance Muscles, exercise and obesity: skeletal muscle as a secretory organ published in Nature Reviews. Endocrinology (2012) and The Role of Exercise-Induced Myokines in Muscle Homeostasis and the Defense against Chronic Diseases.

Exercise can be a double-edged sword

While moderate physical activity seems to boost immune function as compared to sedentary states, excessive high-intensity exercise may have the opposite effect of impairing the immune system (see Immune function in sport and exercise, published in the Journal of Applied Physiology in 2007).

Additionally, overdone or done improperly (such as not adapted to the individual's abilities, without allowing proper rest, etc.), exercise may contribute to cardiovascular and muscular injuries.

As in other areas of life, moderation seems to be the key and any exercise regimen should be tailored to the individual to respect each person's current or inherent limitations.

Exercise alone is not enough

A healthy lifestyle obviously includes other factors besides regular exercise, with a diet adapted to each person's individual requirements ranking among the foremost in importance to health.

Mental exercise as an alternative for the incapacitated?

It is well established that imagining physical movements consistently actually strengthens the muscles involved (see below-listed Studies: Benefits of Mental Training). One cannot rule out that mental training not only effects muscle growth but also stimulates other benefits linked to exercising, so "mental exercising" may be a temporary tide-me-over for individuals currently unable to engage in physical exercise.

STUDIES INTO THE CANCER-PREVENTIVE EFFECT OF EXERCISE

General

The role of physical activity in cancer prevention, treatment, recovery, and survivorship

www.ncbi.nlm.nih.gov/PubMed/23909073

Published in Oncology (Williston Park, NY), in 2013, this review of the scientific literature inter alia shows that cancer incidence decreases when physical activity increases:

Breast, colon, and prostate cancer survivors who exercise after being diagnosed exhibit lower cancer-specific mortality, cancer survivors' all-cause mortality decreases as their exercise levels increase (with amount and intensity of exercise required for survival benefits appaparently varying by tumor type), and exercise can reduce the side effects of chemotherapy, radiation, and surgery and can help in recovery and rehabilitation after conventional cancer treatment. Quote:

"Decreased breast cancer mortality is seen with the equivalent of 3 hours of walking per week, and decreased colon cancer mortality with 6 hours of walking per week." Following a prostate cancer diagnosis, however, it is more intense exercise which correlates with longer survival as compared to simple walking.

Habitual recreational physical activity is associated with significantly improved survival in cancer patients: evidence from the Roswell Park Data Bank and BioRepository.

www.ncbi.nlm.nih.gov/pubmed/30488344

Published in Cancer Causes & Control in 2019, this study done on some 5800 cancer patients showed inter alia that those who exercised three or four times a week before or after diagnosis reduced their risk of dying by nearly 40 %.

Evidence on the prevention of cancer

www.ncbi.nlm.nih.gov/PubMed/23843144

Published in the Revista Espanola de Sanidad Penitenciaria (2013), this Spanish-language study found considerable evidence that "not smoking, regular physical exercise and a diet rich in fruit and vegetables... can reduce the incidence of cancer". Free full text available.

Annual Report to the Nation on the status of cancer, 1975-2008, featuring cancers associated with excess weight and lack of sufficient physical activity

www.ncbi.nlm.nih.gov/PubMed/22460733

Published in Cancer, 2012, this report discusses the contribution of overweight/ obesity as well as insufficient physical activity to increased cancer incidence and burden (in the US), lowered quality of life in cancer survivors, and the possible impact of overweight on prognosis for several types of cancers.

Physical activity and cancer prevention: a review of current evidence and biological mechanisms

www.ncbi.nlm.nih.gov/PubMed/22442921

Published in the Journal of Preventive Medicine and Hygiene (2011), this study concluded that "[i]ncreased leisure-time physical activity is associated with cancer prevention in several organs". Few studies however "indicated a protective role for occupational physical activity in cancer prevention when compared with leisure-time physical activity."

Importance and evidence of regular physical activity for prevention and treatment of diseases

www.ncbi.nlm.nih.gov/PubMed/24150703

Published in the Deutsche Medizinische Wochenschrift (2013), this study focuses on the many prospective cohort studies demonstrating positive effects of regular physical activity on morbidity and mortality, which make exercise a significant part of the prevention and therapy of various diseases incl. cancer. Quote: "...physical exercise acts as a highly efficient drug, and should be used in many diseases."

Effects of physical activity on cancer risk and disease progression after cancer diagnosis

www.ncbi.nlm.nih.gov/PubMed/22286245

Published in the German Bundesgesundheitsblatt, Gesundheitsforschung, Gesundheitsschutz in 2012, this study states that "[n]umerous epidemiologic studies have demonstrated that regular physical activity convincingly reduces risk for colon cancer" and probably and/or possibly for some other cancers, with relative risks reduced from 10 to 30 percent depending on cancer type.

Overall, c. 9 to 19 percent of the most common malignancies are attributable to insufficient exercise, making physical activity a cancer-preventative lifestyle choice of great potential. According to present knowledge, a minimum of 30 to 60 minutes of moderate to vigorous activity a day is recommended.

Even in conventional cancer treatment, physical activity is now considered "feasible, safe, and even recommended in almost all stages of disease". Symptoms such as fatigue, insomnia and depression related to both disease and treatment can be reduced by physical activity as shown in randomized-controlled trials.

Lack of exercise is a major cause of chronic diseases

www.ncbi.nlm.nih.gov/PubMed/23798298

Published in Comprehensive Physiology (2012), this study examined physical activity/exercise as primary prevention against 35 chronic conditions including colon, breast and endometrial cancer, and concluded that "conclusive evidence exists that physical inactivity is one important cause of most chronic diseases... physical activity primarily prevents, or delays, chronic diseases..."

Intensity of leisure-time physical activity and cancer mortality in men

www.ncbi.nlm.nih.gov/PubMed/19656766

This prospective study published in the British Journal of Sports Medicine (2011) "indicates that the mean intensity of leisure-time physical activity is inversely associated with the risk of premature death from cancer in men".

It pays to exercise

www.ncbi.nlm.nih.gov/PubMed/24191810

Published in Nursing Standard (2013), this study inter alia found that physical activity during the course and after conventional cancer treatment can reduce the risk of a relapse as well as death from cancer.

Physical activity and its relation to cancer risk: updating the evidence.

www.ncbi.nlm.nih.gov/PubMed/23991944

Published in the Asian Pacific Journal of Cancer Prevention (2013).

With scientific evidence for the prevention of cancer by physical activity accumulating, this paper summarizes conclusions from epidemiologic studies and presents suggested biological mechanisms incl. decrease in weight, inflammation and sex and metabolic hormones, modified insulin resistance, and improved immune function.

State of the epidemiological evidence on physical activity and cancer prevention

www.ncbi.nlm.nih.gov/PubMed/20843488

Published in the European Journal of Cancer (2010), this study concluded that the evidence for exercise exerting a beneficial effect on colon, breast and endometrial cancer risk was convincing or probable but weaker for lung, prostate and ovarian cancers while being null or insufficient for all other types of malignancy.

Evidence that between 9 and 19 percent of all European cancer cases could be attributed to insufficient physical activity is strong and consistent. For cancer prevention, public health authorities generally recommend 30 to 60 minutes of moderate or vigorous-exercise done at least five days a week.

Studying the connection between exercise and cancer risk reduction

www.ncbi.nlm.nih.gov/PubMed/23682132

Published in the Journal of the National Cancer Institute (2013)

Quoting from the above article: "Leslie Bernstein, Ph.D., submitted a paper that found when younger women exercised for 4 hours per week they lowered their breast cancer risk by 50%... the study was published in 1994. Since then, dozens of studies have associated exercise with reduced risk of breast cancer and many other cancers...

The association is strongest in breast and colon cancer, and evidence is mounting that exercise is associated with lower risk of endometrial, ovarian, prostate, and pancreatic cancer."

Studies: Exercise and Breast Cancer

Significantly greater reduction in breast cancer mortality from post-diagnosis running than walking

www.ncbi.nlm.nih.gov/PubMed/24470442

Published in the International Journal of Cancer in 2014, this study's "results suggest that post-diagnosis running is associated with significantly lower breast cancer mortality than post-diagnosis walking".

Breast cancer mortality vs. exercise and breast size in runners and walkers

www.ncbi.nlm.nih.gov/PubMed/24349006

Published in PLoS One in 2013, this study found that "Breast cancer mortality decreased in association with both meeting the exercise recommendations and smaller breast volume."

This article has been made available for free at www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0080616 .

Obesity, diet and physical inactivity and risk of breast cancer in Thai women

www.ncbi.nlm.nih.gov/PubMed/24377643

Published in the Asian Pacific Journal of Cancer Prevention (2013), results of this case control study following 1,130 cases and 1,142 controls "indicate that obesity and high consumption of animal fat are associated with breast cancer risk ... while recreational physical activity has protective effects."

The entire research article is made available for free at www.apocpcontrol.org/paper_file/issue_abs/Volume14_No11/7023-7027%209.29%20Suleeporn%20Sangrajrang.pdf .

Past recreational physical activity and risk of breast cancer

www.ncbi.nlm.nih.gov/PubMed/15782064

Published in the Clinical Journal of Sport Medicine, 2005, this study analysed 74,171 female subjects between the ages of 50 and 79 (of 93,676 enrolled in the Women's Health Initiative Observational Study [WHIOS], October 1993 to December 1998). It was found that "[m]ore physical activity was associated with a lower risk of breast cancer ... an hour every day of moderate or strenuous activity provided most benefit."

Physical activity and breast cancer risk among Asian-American women in Los Angeles: a case-control study.

www.ncbi.nlm.nih.gov/PubMed/12733156

Published in Cancer (2003), this study found further support for the finding that physical activity plays a protective role in breast cancer.

Studies: Exercise and Colorectal Cancer

Physical activity and colorectal cancer risk: an evaluation based on a systematic review of epidemiologic evidence among the Japanese population.

www.ncbi.nlm.nih.gov/PubMed/22068300

Published in the Japanese Journal of Clinical Oncology (2012), this study concluded that exercise "probably decreases the risk of colorectal cancer among the Japanese population... the evidence for the colon is probable, whereas that for the rectum is insufficient."

Free full text available at http://jjco.oxfordjournals.org/content/42/1/2.long

Physical activity and risk of colon adenoma: a meta-analysis

www.ncbi.nlm.nih.gov/PubMed/21304525

Published in the British Journal of Cancer (2011), this study "confirms previous reports of a significant inverse association of physical activity and colon adenoma, and suggests that physical activity can have an important role in colon cancer prevention".

This meta-analysis can be read in its entirety at www.nature.com/bjc/journal/v104/n5/full/6606045a.html .

Obesity and colorectal cancer

www.ncbi.nlm.nih.gov/PubMed/22289950

Published in The Korean Journal of Gastroenterology (2012), this study states that "obesity acts as an independent significant risk factor for malignant tumors of various organs including colorectal cancer... The relative risk of colorectal cancer of obese patients is about 1.5 times higher than the normal-weight individuals".
Free full text available in Korean

Physical activity reduces risk for colon polyps in a multiethnic colorectal cancer screening population.

www.ncbi.nlm.nih.gov/PubMed/22715975

Published in BMC Research Notes (2012), this examination of 982 patients concluded that exercising just one hour per week reduced the incidence of polyps and adenomas as compared to no or less exercise. Groups at risk for colorectal cancer (such as Blacks) benefit from physical activity, as do overweight and obese individuals. Exercise should be promoted for cancer prevention in multiethnic populations (free full text available).

Studies: Exercise and Prostate Cancer

Possible prevention and treatment of prostate cancer by exercise

www.ncbi.nlm.nih.gov/PubMed/22792655

Published in the West Virginia Medical Journal (2012).

After referring to the established link between exercise and colon and breast cancer prevention and the so far insufficient link to.prostate cancer prevention, this study focuses on the potential of exercise to a) reduce the many potentially bothersome and health-threatening side effects and complications of orthodox prostate cancer treatment and to b) improve survival outcomes and quality of life in prostate cancer patients.

Obesity and prostate cancer: weighing the evidence.

www.ncbi.nlm.nih.gov/PubMed/23219374

Published in European Urology (2013), this study found increasing evidence connecting obesity to higher incidence of aggressive prostate cancer, increased risk of complications from conventional treatment (prostatectomy, radiotherapy, androgen-deprivation therapy) and higher PCa-specific mortality. Animal experimentation shows weight loss slows prostate cancer. (Free full text available)

Physical activity for primary prevention of prostate cancer. Possible mechanisms

www.ncbi.nlm.nih.gov/PubMed/22278169

Published in Der Urologe Ausg. A (2012)

This review of the scientific literature describes potential preventative mechanisms (such as exercise lowering the testosterone levels and modulating calcium, parathormone and vitamin D3 concentrations) and concludes that "[h]igh intensive physical activity may contribute to the prevention of prostate carcinoma".

Potential for prostate cancer prevention through physical activity

www.ncbi.nlm.nih.gov/PubMed/22198724

Published in the World Journal of Urology (2012), this review of 22 epidemiological studies concluded that there is a growing body of research evidence suggesting that exercise has protective effects against prostate cancer.

Epidemiological evidence for preventing prostate cancer by physical activity

www.ncbi.nlm.nih.gov/PubMed/23065019

This analytical review, published in the Wiener Medizinische Wochenschrift (2012), concluded that physical activity in leisure and in work shows no protective benefits but intense physical activity provided effective preventative benefits as corroborated by substantial evidence.

Studies: Exercise and Lung Cancer

Physical activity and lung cancer prevention

www.ncbi.nlm.nih.gov/PubMed/21113762

Published in Recent Results in Cancer Research (2011), this paper reports that exercise (total and recreational physical activity) reduces lung cancer risk by 20-30% in women and 20-50% in men, as supported by the majority of studies.

Nutrition habits, physical activity, and lung cancer: an authoritative review

www.ncbi.nlm.nih.gov/PubMed/23375445

Published in Clinical Lung Cancer (2013), this study inter alia reports results from a meta-analysis conducted from 1996 to 2003 which demonstrated that leisure physical activity prevented lung cancer, as well as results from eleven cohort and case-control studies showing an inverse relationship between lung cancer and fruit and vegetable consumption.

Studies: Exercise and Brain Cancer

Reduced Risk of Brain Cancer Mortality from Walking and Running

www.ncbi.nlm.nih.gov/PubMed/24091993

Published in Medicine and Science in Sports and Exercise (2013), this prospective study examined the possible association of exercising with lowered brain cancer mortality in a total of 150,000 runners or walkers and found that the risk of dying from brain cancer decreased in relation to running or walking energy expenditure.

Studies: Exercise and Kidney Cancer

Reduced risk of incident kidney cancer from walking and running

www.ncbi.nlm.nih.gov/PubMed/23863620

This study published in Medicine and Science in Sports and Exercise in 2014 examined the possible association of incident kidney cancer risk with exercise energy expenditure and concluded that "[r]unning and walking may reduce incident kidney cancer risk".

Physical activity and urologic cancers

www.ncbi.nlm.nih.gov/PubMed/23021556

Published in Urologic Oncology (2012), the study inter alia found that "a growing body of research suggests that physical activity results in a modest risk reduction for kidney cancer".

Studies on the Benefits of Mental Training

Strength gains by motor imagery with different ratios of physical to mental practice

https://pubmed.ncbi.nlm.nih.gov/21897826/

Published in Frontiers in Psychology (2011), this study arrived at the conclusion "that high-intensity strength training sessions can be partly replaced by [mental/imagined] training sessions without any considerable reduction of strength gains".

Benefits of motor imagery training on muscle strength

www.ncbi.nlm.nih.gov/PubMed/20508474

Published in Journal of Strength and Conditioning Research (2010), this study concluded that "athletes may perform imagined muscles contractions ... to contribute to the enhancement of concentric strength".

Strength increases from the motor program-comparison of training with maximal voluntary and imagined muscle contractions.

www.ncbi.nlm.nih.gov/PubMed/1597701

Published in the Journal of Neurophysiology (1992), this study inter alia concluded that "[s]trength increases can be achieved without repeated muscle activation": test subjects that had visualized themselves lifting a weight with one of their fingers over a four week period (at five "mental training" sessions per week) saw that finger actually becoming stronger.

From mental power to muscle power--gaining strength by using the mind

www.ncbi.nlm.nih.gov/PubMed/14998709

Published in Neuropsychologia (2004), this is a similar test as above comparing one group trained to perform "mental contractions" of little finger abduction with one that actually did the same training physically as well as one "do-nothing" group serving as control.

The training spanned twelve weeks (with 15 minute sessions five times a week). At the end, the mental training group was found to have increased their finger abduction strength by 35% and the physical training group by 53%.

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