December 7, 2011 — One third of all cancers are caused by 4 common lifestyle factors — tobacco, diet, alcohol, and obesity.
This finding comes from a detailed review of lifestyle and environmental factors. Researchers calculated the fraction of cancers that can be attributed to each of these factors. The huge study was published as a supplement to the December issue of the British Journal of Cancer.
“This is the most comprehensive review of cancer and lifestyle undertaken to date,” said lead author Max Parkin, MD, professor of epidemiology at Queen Mary University, London, United Kingdom. He was speaking at a press conference held by Cancer Research UK, which sponsored the review.
The review was based on the most recent data available; researchers based their 2010 estimates on British incidence figures from 1993 to 2007. The team then calculated the proportion of cancers that could be attributed to 1 of 14 factors: smoking tobacco, drinking alcohol, lack of fruit and vegetables, lack of fiber, eating red and processed meat, too much salt, being overweight or obese, lack of physical exercise, ionizing radiation, ultraviolet radiation, occupational exposure (e.g., asbestos), infections (e.g., human papillomavirus [HPV]), and — specifically for women — postmenopausal hormone replacement therapy and lack of breast-feeding.
“Many people believe that cancer is down to fate or is ‘in the genes,’ and that it is the luck of the draw whether they get it,” Dr. Parkin said. However, he added, “looking at the evidence, it’s clear that about 40% of all cancers are caused by things we mostly have the power to change.”
The figure is 45% in men and 40% in women; that difference was mostly accounted for by breast cancer in women, Dr. Parkin noted.
In the United Kingdom, this means that around 134,000 cancers annually could be prevented — just over 100,000 of these cases were attributed to tobacco, unhealthy diets, alcohol, and excess weight. Smoking was by far the most important factor, accounting on its own for 60,000 cancers in the United Kingdom each year, or 1 in 5 of all cancers diagnosed, Dr. Parkin emphasized.
Several findings in the review were rather surprising, he said.
“We didn’t expect to find that eating fruit and vegetables would prove to be so important in protecting men against cancer,” he said. “And for women, we didn’t expect being overweight to have a greater effect than alcohol.”