Cancer, Diet and Exercise

Thursday, 06/05/2010  |   Breast Cancer, Lung Cancer, Prostate Cancer  |  no comments

Diet is thought to be one of the most important contributing factors to cancer risk. The contribution of diet to cancer is linked to genetic factors but little has been shown as to cancer survival and diet (Bingham & Riboli 2004). One of the first thing patients ask about in a consultation after a diagnosis of cancer is ‘what diet should I follow’? I tell them that there is no diet that has been proven to alter tumours, to any great degree once they have been established. Yes, a good balanced diet will help along with other interventions but an extreme diet of only raw foods or a complete vegan diet won’t help and quite likely will cause harm. What I do tell them is good, hard regular exercise will help and there is ample evidence to this fact. Pinto and Hartman (2010) have done an amazing literature search on the subject in Psycho-Oncology and have shown exercise has both protective as well as curative benefits. Over 200 population based studies have linked physical activities to cancer risk. The most researched cancers are those of the:

Bowel
Breast
Endometrium
Prostate
Testes
Lung
In bowel cancer the plausible mechanisms of protection include the beneficial effects of exercise on levels of the following substances, which influence the growth and proliferation of cells in the colon:
Insulin
Prostaglandins
Bile acid
In Breast and Endometrial cancers, these strongly hormone-dependent cancers demonstrate that endogenous sex hormones are strongly implicated in their development. Physical activity may modulate the production, metabolism, and excretion of these hormones, so an association with these cancers is biologically possible. Physical activity may also reduce the risk of cancer through its normalising effect on body weight and composition. Evidence from population based studies suggests that occupational, leisure, and household activities are associated with about a 30% reduction in breast cancer rates (Friedenreich et al 1998; Shephard et al 1997; McTiernan et al 1998).

Also quality of life (QoL) is a critical issue. With almost 8 million Americans alive today who have been through the cancer experience, it is important to develop interventions to maintain quality of life (QOL) following cancer diagnosis. Physical exercise is an intervention that may address the broad range of QOL issues following cancer diagnosis including physical, functional, psychological, emotional, and social well-being. Studies have consistently demonstrated that physical exercise has a positive effect on QOL following cancer diagnosis, including physical and functional well-being (e.g. functional capacity, muscular strength, body composition, nausea, fatigue) and psychological and emotional well-being (e.g. personality functioning, mood states, self-esteem, and QOL). Besides overcoming the limitations of past research, recommendations for future research included: (a) extending the research beyond breast and early-stage cancers; (b) comparing and integrating physical exercise with other QOL interventions; (c) examining resistance exercises, the timing of the intervention, and contextual factors; (d) expanding the breadth of the QOL indicators examined; and (e) investigating the rates and determinants of recruitment and adherence to an exercise program following cancer diagnosis (Courneya & Friedenreich 1999). Preliminary research suggests that exercise may be an effective intervention for enhancing quality of life (QOL) in cancer survivors (Courneya 2003).
Fairey et al (2002) in their review found six empirical studies published between 1994 and 2000 that have examined physical exercise and immune system function in cancer survivors. Overall, four out of six studies reported statistically significant improvements in a number of cancer-related immune system components as a result of exercise.

In a completely different study it was found that diet without exercise does not help weight loss. 18 adult ovariectomised female monkeys were placed on a low-fat diet, and available calories were reduced by 30% compared with baseline consumption for 1 mo. Surprisingly, there was not significant weight loss; however, daily activity level (measured by accelerometry) decreased soon after diet initiation and reached statistical significance by the 4th wk of dieting (18 +/- 5.6% decrease, P = 0.02). During a 2nd mo of dieting, available calories were reduced by 60% compared with baseline consumption, leading to 6.4 +/- 1.7% weight loss and further suppression of activity. Metabolic rate decreased by 68 +/- 12 kcal/day, with decreased activity accounting for 41 +/- 9 kcal/day, and the metabolic activity of the weight lost accounting for 21 +/- 5 kcal/day. A second group of three monkeys was trained to run on a treadmill for 1 h/day, 5 days/wk, at 80% maximal capacity, leading to increased calorie expenditure of 69.6 +/- 10.7 kcal/day (equivalent to 49 kcal/day for 7 days). It was concluded that a diet-induced decrease in physical activity is the primary mechanism the body uses to defend against diet-induced weight loss, and undertaking a level of exercise that is recommended to counteract weight gain and promote weight loss is able to prevent the compensatory decrease in physical activity-associated energy expenditure that slows diet-induced weight loss (Sullivan & Cameron 2010).

References
Bingham, S. & Riboli, E. Diet and cancer — the European Prospective Investigation into Cancer and Nutrition. Nature Reviews Cancer 4, Pp. 206-15. 2004 doi:10.1038/nrc1298
Courneya, K.S. Exercise in Cancer Survivors: An Overview of Research. Med. Sci. Sports Exerc., Vol. 35, No. 11, pp. 1846-1852, 2003.
Courneya, K.S. & Friedenreich, C.M. Physical exercise and quality of life following cancer diagnosis: A literature review. Annals of Behavioral Medicine. Volume 21, Number 2 / June, 1999. Pp.171-9. DOI:10.1007/BF02908298
Fairey, A.S., Courneya, K.S., Field, C.J. & Mackey, J.R. Physical exercise and immune system function in cancer survivors
Cancer. 2002 Vol 94 Issue 2, Pp. 539-51. DOI:10.1002/cncr.10244
Friedenreich, C.M., Thune, I., Brinton, L.A. & Albanes, D. Epidemiologic issues related to the association between physical activity and breast cancer. Cancer 1998; 83: 600-610.
McTiernan, A., Ulrich, C., Slate, S. & Potter, J. Physical activity and cancer aetiology: associations and mechanisms. Cancer Causes Control 1998; 9: 487-509.
Shephard, R.J. & Futcher, R. Physical activity and cancer: How may protection be maximised? Crit Rev Oncog 1997; 8: 219-272.
Sullivan, E.L. & Cameron, J.L. A rapidly occurring compensatory decrease in physical activity counteracts diet-induced weight loss in female monkeys. Am J Physiol Regul Integr Comp Physiol. 2010 Apr;298(4):R1068-74.
Pinto, B.M. & Hartman, S.J. Exercise and Cancer Chapter 4 In Psycho-Oncology. Editors: Jimmie C. Holland, William S. Breitbart, Paul B. Jacobsen, Marguerite S. Lederberg, Matthew J. Loscalzo and Ruth McCorkle. Oxford University Press, USA; 2 edition (March 22, 2010)

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