Women who drink coffee could be protecting themselves against an aggressive form of breast cancer, research suggests.
Coffee drinkers are far less likely to develop oestrogen-receptor negative breast cancer, particularly if they drink five cups or more a day.
These types of tumours do not react to a wide range of drugs, meaning chemotherapy is often the only option.
In the study, experts from the Karolinska Institute in Stockholm found coffee drinkers had a lower incidence of breast cancer than women who rarely drank coffee. They analysed data from almost 6,000 women who were past the menopause.
Those women who drank five or more cups a day had a 57 per cent reduced risk of breast cancer compared with those who drank less than one cup a day.
Writing in the journal Breast Cancer Research, the researchers concluded: “A high daily intake of coffee was found to be associated with a statistically significant decrease in oestrogen-receptor negative breast cancer among post-menopausal women.”
The authors also found a small reduced risk for all types of breast cancer, although this link was not significant when factors such as age and weight were taken into account.
Previous studies have suggested coffee cuts the risk of other cancers, including of the prostate and liver.
However, experts are divided on the benefits of drinking coffee because some studies have shown it could act as a promoter of cancer.
Some studies suggest coffee may cause cells to proliferate or prevent them from being repaired.
Today’s experts said they suspected coffee may contain compounds that affect different types of breast cancer.
It is possible that coffee fuels oestrogen-receptor positive breast cancers but reduces the risk of oestrogen-receptor negative breast cancer, they said.
This would match the finding that drinking coffee could reduce the risk of breast cancer overall, although the experts said further studies were needed.
Caitlin Palframan, senior policy and information officer at Breakthrough Breast Cancer, said: “It’s interesting that this research suggests coffee could reduce the risk of (oestrogen) negative breast cancer.
“Not all studies agree on the effects of consuming coffee and therefore we wouldn’t encourage women to increase the amount of coffee they drink to protect against breast cancer.
“We do know that women can reduce their chances of developing breast cancer by maintaining a healthy weight, cutting back on alcohol and getting regular physical activity. “We’d recommend women have a healthy, balanced diet - which could include coffee – for overall good health.” Figures suggest that around one in four women diagnosed with breast cancer will have oestrogen-receptor negative breast cancer.