Physical activity can curb many a cancer

The above heading is original to the article below but is deceptive. See why at the foot of the article

Health promotion campaigns have helped the Australian public become increasingly aware of the benefits of physical activity and exercise for improving or maintaining health. Most messages are focused on the importance of exercise for the prevention and management of conditions such as heart disease or diabetes. Surprisingly, little is mentioned of the significant impact of exercise on the nation's leading cause of death - cancer. Furthermore, cancer sufferers themselves may not be aware of the mounting evidence that physical activity significantly improves survival rate.

The lifetime risk of cancer for Australians is one in three for males and one in four for females. With 88,000 new cases diagnosed each year, it accounts for 30 per cent of all male and 25 per cent of all female deaths. Prostate cancer is the most common cancer in men, followed by lung and colon. For women, breast cancer is the most common, followed by lung and colorectal.

There is growing evidence that a number of lifestyle factors contribute to the much higher incidence of cancer in developed nations such as Australia - particularly physical inactivity, low consumption of fibre and folate, and a high consumption of saturated fats and red meat. While physical activity reduces the risk of developing various cancers, obesity has been linked to an increased risk of cancer, as well as poorer survival rates (Cancer 2006;107(3):632).

However, growing evidence supports physical activity not only for prevention of cancer, but for significantly improving survival rates. A study published last year in the Journal of the American Medical Association involving 2987 women diagnosed with breast cancer rocked the scientific community when it revealed that walking 3-5 hours per week reduced the risk of dying from the cancer by 40 per cent (2005;293(20):2479).

The growing body of research was added to this year with two separate studies on colorectal cancer in the Journal of Clinical Oncology (2006;24:3527 and 2006;24:3535). Both investigated the association between physical activity undertaken after diagnosis and its relationship with survival, and found that there was a 50-60 per cent reduction in both the recurrence of the cancer and overall mortality compared to those who were sedentary.

These results have significant implications for cancer therapy, as bowel cancer is the most frequently occurring internal cancer with more than 13,000 people diagnosed each year. An aggressive cancer, only 56 per cent of people with the condition survive five years after diagnosis.

Although the physiological effects of exercise on cancer survival are not yet understood, there are various proposed mechanisms including improved hormone regulation, decreases in blood insulin levels, enhanced anti-tumour immune function and a decrease in free-radicals. Regardless of the mechanism, what is certain is that it does have a positive impact, and there are calls for greater promotion of physical activity and exercise for both prevention and treatment.

A study published in the Health Promotion Journal of Australia last year revealed that two in three people were motivated to increase their physical activity if they believed it could reduce their risk of bowel cancer. Based on these findings, it would be reasonable to assume that cancer sufferers informed of the research linking exercise to improved survival rates would be motivated to a greater extent to increase their physical activity. However, the study's author, doctor Geoffrey Jalleh, claimed that cancer organisations did not actively promote the protective effects of physical activity on common cancers including bowel and breast. "As a result, the general public's awareness of the links between physical inactivity and increased risk for cancer is minimal."

What is clear is that if physical activity can have a similar effect as trastuzumab - an agent for the treatment of breast cancer, and sold under the brand name Herceptin - then exercise needs to undergo an investigative process similar to the development of a medication. Further research is needed to determine the optimal dose of exercise for each type of cancer, the ideal type of activity (strength training versus cardiovascular exercise), and potential side effects.

Preliminary data shows that exercise reduces the side effects associated with cancer treatment, and is quite safe as a treatment modality (Support Cancer Care 2006;14:732). However, in a recent review, a major barrier identified to promoting physical activity in cancer patients is the confidence level of the treating oncologist to provide their patient with appropriate exercise advice. Considering that this review was conducted in the US, this problem may be overcome in Australia through a partnership-based approach between the oncologist and exercise physiologist, providing the basis for better health outcomes and greater research.

As leading cancer and exercise researcher Demark-Wahnefried recently stated in the Journal of Oncology: "There is no doubt that the pharmaceutical industry would back an agent with potential to reduce cancer recurrence by at least 50 per cent, but who will back a trial that evaluates the potential benefits of sneakers and sweatpants?"

Source

The author above is Chris Tzar, an exercise physiologist and director of the Lifestyle Clinic, Faculty of Medicine, University of NSW, so an excess of enthusiasm for his chosen field can perhaps be forgiven. He gives the impression above that exercise can prevent all sorts of cancers. That is not true. All the studies he notes above refer to people who ALREADY HAVE cancer, a population that is by definition different from the population as a whole.

There is however other evidence on whether exercise prevents cancer and it shows good evidence for benefit in the case of colon cancer only. Even rectal cancer occurrence is unrelated to exercise. There is also some evidence that exercise is a preventive for breast cancer in women -- but so is being fat a preventive for breast cancer in women. So a woman who has a family history of breast cancer would be at least as well advised to eat plenty of Big Macs and KFC as to exercise. I think I can say with absolute certainty, however, that you would never hear that advice from Mr Tzar, correct though it is. That would be completely against the prevailing religion. He is good at hinting at bias in others (see his last sentence above) but I doubt that he sees his own biases as any problem.

Clearly however, men with a family history of colon cancer should exercise as long as they do not have counterindications for it as well

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