Just half a glass of wine or a small beer a day increases the risk of breast cancer, a new report has claimed.
The study, by the World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR) found convincing evidence a healthy diet, exercise, limiting alcohol and watching your weight can all reduce the risk of breast cancer.
Experts found strong evidence that taking vigorous exercise (such as running or biking) cut the risk of pre-menopausal breast cancer by 17 per cent compared to women who were least active, and led to a 10 per cent drop for post-menopausal breast cancer.
Meanwhile, breastfeeding had a strong relationship with decreasing the risk of both types of the disease.
There was also "limited but suggestive" evidence eating non-starch leafy vegetables such as cabbage, kale, rocket and spinach decreased the risk oestrogen-receptor (ER) negative breast cancer, a less common type of tumour but one that was harder to treat. Consuming foods high in carotenoids, such as carrots, tomatoes, apricots, spinach and sweet potatoes, was also linked to a lower risk of breast cancer, as were dairy foods and others high in calcium.
But there was strong evidence that just a small amount of wine or beer a day (about 10g of alcohol) increased the risk of pre-menopausal breast cancer by 5 per cent and pushed up the risk by 9 per cent in the case of post-menopausal.
In the UK, beers, wines and spirits are measured as units, with one unit being 8g of pure alcohol. A one-unit-sized alcoholic drink is approximately equivalent to 250ml of 4 per cent strength beer, 76ml of 13 per cent wine, or 25ml of spirits.
The study also found being overweight or obese increased the chance of post-menopusal breast cancer, but cut the risk of pre-menopausal breast cancer if people were overweight in their younger years.
Dr Anne McTiernan, a lead author of the report and cancer prevention expert at the Fred Hutchinson Cancer Research Centre in Seattle, said: "With this comprehensive and up-to-date report the evidence is clear: Having a physically active lifestyle, maintaining a healthy weight throughout life and limiting alcohol are all steps women can take to lower their risk."
She explained that the links between food and breast cancer were intriguing but needed further research.
"The findings indicate women may get some benefit from including more non-starchy vegetables with high variety, including foods that contain carotenoids," she said. "That can also help avoid the common one to two pounds women gain every year, which is key for lowering cancer risk."