As many as 23% of colorectal cancers could be prevented if people followed five simple healthy lifestyle recommendations, Danish researchers say.
The recommendations - which would improve overall health as well - include exercise, a good diet, moderate drinking, no smoking and maintaining a healthy weight, the researchers say.
"Even a modest difference in your lifestyle habits may have a substantial impact on your colorectal cancer risk," said lead researcher Dr Anne Tjonneland of the Institute of Cancer Epidemiology of the Danish Cancer Society in Copenhagen.
Specifically, the recommendations are:
At least 30 minutes of exercise a day.
No more than seven drinks a week for women and 14 for men.
Eating a healthful diet, defined as one high in fibre, with more than six servings (three cups) a day of fruits and vegetables, and low in red meat and processed meat (no more than just over a pound a week), with less than 30% of total kilojoules derived from fat.
A waist size no more than 34.6 inches for women and 40.1 inches for men.
The report is published in the BMJ.
For the study, Tjonneland and colleagues examined data on 55,487 men and women aged 50 to 64, who had not been diagnosed with cancer.
All those in the study completed a lifestyle questionnaire, which asked about social factors, health status, reproductive factors and lifestyle habits. They also completed a food frequency questionnaire that detailed what they ate over 12 months.
During 10 years of follow-up, 678 people developed colorectal cancer.
If all the participants (except for the healthiest men and women) had adopted just one additional lifestyle recommendation, 13% of the colorectal cancer cases could have been avoided, the researchers found.
"For each additional lifestyle recommendation the participants followed, a reduction of 13% [in colorectal cancer] was shown," Tjonneland said.
And if all those in the study had followed all five lifestyle recommendations, then there would have been 23% fewer colorectal cancer cases, Tjonneland's group found.
"The hope is that this is an understandable message leading to an impact in the prevention of colorectal cancer," she said.
Marji McCullough, strategic director of nutritional epidemiology at the American Cancer Society, said that "the study shows the importance of following cancer prevention guidelines for lifestyle."
"The majority of these cancers and deaths can be prevented by applying existing knowledge about cancer prevention, such as lifestyle and by increasing the use of established screening tests," McCullough said. "Colorectal cancer is a highly preventable cancer."
'Not asking people to be triathletes'
Dr Floriano Marchetti, an assistant professor of clinical surgery in the division of colon and rectal surgery at the University of Miami's Sylvester Comprehensive Cancer Center, added that "this study confirms on a large scale what the impression of many other small studies have only hinted at."
"If you look at these lifestyle recommendations, they are not really horrible," he said. "This is not like people are asked to be on a strictly vegetarian diet or become triathletes."
And the benefit is linear, Marchetti pointed out. "You modify something and you already have a return with minimal investment. If you modify more, you have a better return," he said.
In another study in the same issue, Australian researchers found that people without a high school diploma who received information about colon cancer screening through a decision aid featuring an interactive booklet and DVD, ended up more informed than those who received only standard screening information. However, the former group was less likely to get screened.
Although the decision aid did not encourage more people to undergo screening, at least it gave them the data they needed to make an informed choice, the researchers said.
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