Wednesday, December 13, 2006

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?"


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

Low fat warning

Dieters who use low-fat foods to try to cut their weight can consume up to 45% more calories than they intend, researchers have found, writes Jonathan Leake. They warn that such foods can make people put on weight, because the fats are replaced with sugars or other nutrients that contain nearly as many calories as the original version. Additionally, it is the fats in a food that create a feeling of fullness, so their absence can encourage people to keep on eating even more than they normally would.

"People don't realise that low-fat foods are not always low-calorie foods," said Brian Wansink, professor of marketing and nutritional science at Cornell University in New York, who carried out the research. "Fat is often replaced with sugar. Low-fat snacks are an average of 11% lower in calories, but people wrongly believe they are 40% lower." He found that when offered low-fat snacks rather than regular ones obese people ate up to 45% more calories.



Shoppers are continuing to pile their trolleys and baskets with unhealthy food, despite the Government's focus on tackling Britain's obesity crisis. A survey of food-buying patterns of 12 million consumers has found that, in the past four years, 44 per cent of people have made no change to their eating habits. Only 8 per cent of shoppers have moved towards a healthier diet, while almost as many are deliberately shunning a good diet and eating more junk food. Even shoppers who normally try to eat healthily fall off the wagon if there is an upheaval in their lives such as the arrival of a new baby, divorce, a wedding, moving house, losing a job or being promoted at work.

The findings, from dunnhumby, the retail consultants, who have scrutinised the sales data of 10,000 everyday ingredients clocked up on Tesco loyalty cards as well as interviewed 2,000 customers, suggest that it will take more than a generation before Britain becomes a nation of healthy eaters. The findings will come as a blow to the efforts of Caroline Flint, the Public Health Minister, and the Food Standards Agency, who are attempting to encourage people to eat a more nutritious diet.

The study also appears to suggest that consumers need the help of the agency's traffic-light system of red, amber and green alerts on packs to help them to choose a healthier mix of food. The traffic lights are being strongly opposed by food manufacturers and Tesco, who claim that the system is simplistic and demonises food.

A surprising feature of the study is that there is little difference in the cost of a healthy shopping basket and an unhealthy one. A typical healthy basket costs an average 71.78 pounds compared with 71.18 pounds for an unhealthy one. Healthy shoppers were identified for buying organic and ecofriendly products and food with labels such as fresh, lite or low fat, or food from the healthy-living ranges. [The mugs who believe anything, in other words]

Unhealthy baskets typically contained value or extra lines, indicating that people were looking for the cheapest food that they could find. It suggests that many shoppers still think that healthy eating is expensive. But shoppers also enjoy a treat, and sales of chocolate and alcoholic drinks have shown no decline. They also like to "scrimp and splurge". Researchers identified people who chose cheaper products to pay for a treat, either a cream cake, gourmet food for a pet or a DVD.

Martin Hayward, director of consumer strategy for dunnhumby, said: "Most of us are neither totally healthy nor totally unhealthy eaters." He said that worry about the cost of food prevented many people from eating healthily and yet the analysis had shown that there was little difference in the price of a healthy versus unhealthy basket. Mr Hayward said: "We believe the distance between healthy and unhealthy eating is because people don't know how to cook and have a `can't cook, won't cook' approach, making them heavily reliant on processed foods and ready meals."

The findings are intended to explore new ways to help consumers to eat a healthy diet, he said. The analysis also bolsters policy statements from Tony Blair and David Cameron, the Conservative leader, who have promised to bring cookery classes back into schools.



Just some problems with the "Obesity" war:

1). It tries to impose behavior change on everybody -- when most of those targeted are not obese and hence have no reason to change their behaviour. It is a form of punishing the innocent and the guilty alike. (It is also typical of Leftist thinking: Scorning the individual and capable of dealing with large groups only).

2). The longevity research all leads to the conclusion that it is people of MIDDLING weight who live longest -- not slim people. So the "epidemic" of obesity is in fact largely an "epidemic" of living longer.

3). It is total calorie intake that makes you fat -- not where you get your calories. Policies that attack only the source of the calories (e.g. "junk food") without addressing total calorie intake are hence pissing into the wind. People involuntarily deprived of their preferred calorie intake from one source are highly likely to seek and find their calories elsewhere.

4). So-called junk food is perfectly nutritious. A big Mac meal comprises meat, bread, salad and potatoes -- which is a mainstream Western diet. If that is bad then we are all in big trouble.

5). Food warriors demonize salt and fat. But we need a daily salt intake to counter salt-loss through perspiration and the research shows that people on salt-restricted diets die SOONER. And Eskimos eat huge amounts of fat with no apparent ill-effects. And the average home-cooked roast dinner has LOTS of fat. Will we ban roast dinners?

6). The foods restricted are often no more calorific than those permitted -- such as milk and fruit-juice drinks.

7). Tendency to weight is mostly genetic and is therefore not readily susceptible to voluntary behaviour change.

8). And when are we going to ban cheese? Cheese is a concentrated calorie bomb and has lots of that wicked animal fat in it too. Wouldn't we all be better off without it? And what about butter? It is just about pure fat. Surely it should be treated as contraband in kids' lunchboxes! [/sarcasm].

9). For a summary of the weak science behind the "trans-fat" hysteria, see here. Trans fats have only a temporary effect on blood chemistry and no lasting harm from them has ever been shown.


1 comment:

Chuck said...

I love your blog. It's very infomative about eating more fruits, and vegetables