The study, published in Breast Cancer Research, suggests that drinking over five cups of coffee per day may significantly reduce the risks of developing a sub type of breast cancer known as anti-oestrogen-resistant oestrogen-receptor (ER-negative) breast cancer.
The team of Swedish researchers, based at the Karolinska Institutet, compared lifestyle factors including coffee consumption between women with breast cancer and age-matched women without, finding that coffee drinkers had a lower incidence of breast cancer than women who rarely drank coffee.
“We found no evidence that coffee consumption increases the overall risk of postmenopausal breast cancer. However, a high daily intake of coffee was found to be associated with a significant decrease in ER-negative breast cancer among postmenopausal women,” wrote the researchers, led by Jingmei Li.
The authors reported that five cups of coffee per day were 57 per cent less likely to develop ER-negative breast cancer than a low consumption reference group.
Coffee and cancer
Breast cancer is a complex disease which can be sub-divided into hormone-responsive (estrogen receptor (ER) positive) and non-hormone-responsive subtypes (ER-negative) sub types.
However, Li and her colleagues noted that some evidence has suggested that there is a link between coffee consumption and breast cancer risk, according to different oestrogen receptor subtypes.
Coffee is one of the most popular beverages in the world, with production amounting to 7.4 billion kg in 2009/2010, according to the International Coffee Organization.
The Swedish team noted that coffee “is interesting in the light of breast cancer aetiology because of its complex make-up of chemicals, several of which have been shown in experimental studies to have cancer risk altering potential through meaningful biological mechanisms.”
However, they added that the scientific community “stands divided over toxicity of the beverage.”
Previous experimental and clinical studies have suggested that coffee – a complex mixture of caffeine and polyphenols – may play a dual role as both a carcinogen and a chemo-preventive agent.
The new researcher assessed the association between coffee consumption and postmenopausal breast cancer risk in a large population-based study of nearly 6,000 people.
The authors reported that coffee consumption was associated with a modest decrease in overall breast cancer risk.
When separated by breast cancer sub types, Li and her co-workers found a significant reduction in the risk of ER-negative breast cancer for ‘heavy coffee drinkers’ who consume more than five sups per day.
The researchers noted that the risk of breast cancer risk reduction associated with high coffee consumption was significantly higher for ER-negative compared to ER-positive cancer.
Li and her colleagues added that future studies should now be conducted to confirm the effects of coffee consumption with respect to breast cancer subtypes.
Source: Breast Cancer Research
“Coffee consumption modifies risk of estrogen-receptor negative breast cancer”
Authors: J. Li, P. Seibold, J. Chang-Claude, D. Flesch-Janys, et al