Scientists have demonstrated conclusively that tobacco causes cancer. Beyond that, they have established only that relationships exist between cancers and such influences as alcohol consumption, diet, exercise and environmental contaminants. Theories come and go, but here is some of the latest thinking on how to avoid cancer.
TOBACCO AND ALCOHOL:
Simply put, butt out. Smoking causes not only lung cancer but also tumours of the mouth, tongue, throat and lips. What’s more, McGill University epidemiologist Eduardo Franco says prolonged smoking may also lead to a buildup of cancercausing agents in the bladder, pancreas, cervix, rectum and genitalia. Alcohol is a different matter. While it is not a primary cause of cancer, Franco says, it can pro-
mote the development of the disease because it increases the capacity of cells to absorb and carry cancerous agents. “If a person smokes and drinks on a frequent basis,” says Franco, “the risk is overwhelmingly greater than if you’re doing one or the other.”
DIET: The Canadian Cancer Society recommends consumption of five to 10 helpings of fruit and vegetables daily, based on numerous
studies showing that plant fibre reduces the risk of developing colorectal tumours. But even with fibre, there is conflicting evidence. A study published last month in the British medical journal Gut concluded that the fibre found in cereals and processed
granola bars provides no protection. In another diet issue, Dr. Robert Bruce, a University of Toronto researcher, has led groundbreaking studies linking overeating to colon, prostate and breast cancer. Bruce says excessive food intake triggers complex chemical reactions that lead to the production of too much insulin, a hormone that, among other things, makes cells divide and i j proliferate. x
EXERCISE: Several studies over the past two decades have linked exercise with reduced risk of breast and colorectal cancer, but researchers continue to examine the issue. Christine Friedenreich, an epidemiologist with the Alberta Cancer Board, is about to publish results of a study of 2,500 women showing that those who had a lifelong regimen of at least moderate physical activity had a
40-per-cent reduction in risk of breast cancer. “There hasn’t been much research on the underlying biology,” she says. “There are just a bunch of hypotheses.”
There hasn’t been enough research to establish or rule out connections between cancer and the chemicals in our air, water and food, says Kristan Aronson, an epidemiologist
at Queen’s University in Kingston, Ont. Studies have shown that byproducts of the chlorination of water, such as trihalomethanes, may cause colon and bladder cancer. Another set of common chemicals, the organochlorines (including dioxins) found in pesticides, has been linked to tumours in soft tissue such as muscle and fat. But on May 5, Aronson released an analysis of 30 studies finding no
connection between these chemicals and breast cancer.
SCREENING: Early detection is one of the best methods of treating and stopping cancer. The Pap test has led to a 75per-cent reduction in the incidence of cervical cancer since the early 1960s, says Franco, while mammograms appear to have cut the mortality rate from breast cancer by 30 per cent over the same time period. Studies are also beginning to show that screening can detect colorectal cancer in people over 50. But medical professionals are divided on the usefulness of prostate screening, pardy because the current tests can’t determine whether an enlargement of the gland is due to a tumour or other cause.
The story you want is part of the Maclean’s Archives. To access it, log in here or sign up for your free 30-day trial.
Experience anything and everything Maclean's has ever published — over 3,500 issues and 150,000 articles, images and advertisements — since 1905. Browse on your own, or explore our curated collections and timely recommendations.WATCH THIS VIDEO for highlights of everything the Maclean's Archives has to offer.