More than four out of 10 cases of breast cancer in the UK could be prevented if women adopted healthier lifestyles, according to a leading medical charity.
The estimate, by the World Cancer Research Fund (WCRF), is based on its latest review of global research linking the disease to excessive alcohol intake, lack of exercise and being overweight.
Breastfeeding babies also emerges from the study as an important means of reducing the chance of developing breast cancer – a condition that kills about 12,000 women in the UK each year.
The compilation of more than 950 research papers from around the world provides the strongest evidence so far that women's lifestyle choices influence the risk of contracting the disease.
The report, published today, updates a major cancer prevention study released in 2007 that examined different types of cancer.
That review drew on 873 breast cancer studies. Scientists at Imperial College London have now added a further 81 studies published in the last few years.
Professor Martin Wiseman, medical and scientific adviser for the WCRF, said the expanded report "represents the clearest picture we have ever had" of how lifestyle affects a woman's risk of breast cancer.
"This means we are now more sure than ever before that by limiting the amount of alcohol they drink, maintaining a healthy weight and being physically active, women can make a significant difference to their risk," he said. "We estimate over 40% of breast cancer cases in the UK could be prevented just by making these relatively straightforward changes. About 45,000 women are diagnosed with breast cancer every year in the UK, so it is clear these changes could make a big difference."
A WCRF spokesman added: "There's very convincing evidence of the role breastfeeding plays in reducing the risk of breast cancer.
"The main messages from our last study have not changed but the evidence is stronger. We estimate that 42% of all breast cancers in the UK could be prevented through reducing alcohol consumption, exercise and [weight control]."
Patterns of the disease differ around the world. Paradoxically, China – where the population already consumes a better diet and takes more exercise – has less ability to reduce the incidence of breast cancer.
The charity recommends that both men and women aim to be as lean as possible without becoming underweight. A healthy body mass index (BMI) is between 18 and 25. The WCRF advises people to remain close to the lower end of the scale.
The charity also recommends at least 30 minutes of exercise a day and, if alcohol is drunk at all, it be limited to two drinks a day for a man and one for a woman.
The latest study on breast cancer is part of a continuous update project run by the WCRF. Bowel cancer and prostate cancer will now be studied, with updates on these due to become available in 2010.
Marilyn Gentry, chief executive of the WCRF, said: "We believe it is important that people have access to advice that is based on the latest scientific research.
"These are still quite early stages in the project but once it is fully up and running it will mean that people all over the world will always have access to up-to-date advice about how they can make lifestyle changes that can reduce their risk of cancer."
Arlene Wilkie, director of research and policy at Breast Cancer Campaign, said: "This review provides further evidence that maintaining a healthy weight throughout life along with regular physical exercise will reduce the risk of many health problems, including breast cancer, heart disease, high blood pressure, diabetes, arthritis and other types of cancer.
"Although age is the biggest single risk factor – 80% of breast cancers are diagnosed in women over the age of 50 – being overweight after the menopause increases your risk even further."
