From Featuring Dr Chris Steele MBE

Excess weight fuels breast cancer

More than alcohol and smoking

Being overweight is the biggest risk factor for breast cancer in older women, according to new research.

Extra weight has the biggest influence on the levels of female sex hormones in post menopausal women, followed by cigarettes and alcohol.

A study by researchers at Oxford University examined data from 13 separate studies to find the factors which affect the levels of female sex hormones in post menopausal women, a group known to be at higher risk of breast cancer.

Female sex hormones such as oestrogen can fuel the growth of some types of breast tumours.

A woman's body mass index (BMI), a measure of whether you are of healthy weight in relation to your height, was found to be the biggest influence on sex hormone levels, especially oestrogen.

Alcohol was also found to have an impact on hormone levels. Women who drank 20g of alcohol or more per day (around two and a half units) had higher levels of all hormones. A large 250ml glass of wine (12 per cent) contains 3 units of alcohol.

The higher oestrogen levels may contribute to the increased risk of breast cancer in regular drinkers.

Women who smoked 15 cigarettes a day also had moderately higher levels of all hormones than non-smokers.

However, the biggest increases seen were for oestrogens. This may explain why post menopausal, obese women are at higher risk for breast cancer, the researchers said.

Dr Gillian Reeves, who took part in the study, said: “Our study shows that changes in hormone levels might explain the association of established risk factors such as obesity with breast cancer risk."

Dr Julie Sharp, at Cancer Research UK, which funded the study, said: "This is an important study as it helps to show how alcohol and weight can influence hormone levels. Understanding their role in breast cancer is vital and this analysis sheds light on how they could affect breast cancer risk.

“We know that the risk of the disease can be affected by family history and getting older, but there are also things women can do to help reduce the risk of the disease. Maintaining a healthy body weight and reducing alcohol consumption are key to reducing breast cancer risk.”

The study is published in the British Journal of Cancer.

This article was published on Wed 20 July 2011