Just two cups of coffee a day could halve the risk of breast cancer returning in women recovering from the disease , a study has found . Researchers found coffee can stop the growth of tumours in women who have already been treated with the drug tamoxifen . Tamoxifen is the main hormonal therapy drug given to women who have not been through the menopause , and is usually taken for five years or longer after treatment for breast cancer . Just two cups of coffee a day can halve the risk of breast cancer returning and boosts the effect of the drug tamoxifen , researchers found . Most breast cancer tumours rely on the hormone oestrogen to grow , and tamoxifen blocks oestrogen from reaching the cancer cells . This means the cancer either grows more slowly or stops growing altogether . As part of the study , Swedish and British researchers looked at data from 1,090 breast cancer patients , in a follow up of a similar study carried out two years ago . They found that more than 500 women who had been treated with tamoxifen , and those that had drunk at least two cups of coffee a day , had only half the risk of their cancer returning than those who drank less coffee , or none at all . Ann Rosendahl , a researcher from Lund University who carried out the study , said : 'The study also shows that those who drank at least two cups of coffee a day had smaller tumours and a lower proportion of hormone-dependent tumours . 'We saw that this was already the case at the time of diagnosis . ' Researchers also looked more closely at two substances that usually occur in coffee – caffeine and caffeic acid . They found the breast cancer cells reacted to these substances , especially caffeine . Caffeine caused the cells to divide less frequency , and die more often , especially when it was drunk in combination with tamoxifen . The study found caffeine caused breast cancer cells to divide less frequently and die more often . Ms Rosendahl said : 'This shows that these substances have an effect on the breast cancer cells and turn off signalling pathways that the cancer cells require to grow . ' The team demonstrated both in in breast cancer patients and at cell level that coffee can reinforce the effect of treatment with tamoxifen . However , they emphasise the importance of taking prescribed medication . Ms Rosenhal added : 'They are incredibly important , but if you like coffee and are also taking tamoxifen , there is no reason to stop drinking it . 'Just two cups a day is sufficient to make a difference . ' This is not the first study to link coffee consumption with improved cancer prognosis . Drinking coffee may reduce the risk of cancer in heavy drinkers , research has found . A World Cancer Research Fund study shows the hot drink can protect against liver cancer , which is often associated with alcohol abuse . For each cup consumed a day , there is about a 14 per cent decreased risk of liver cancer , found the study by the World Cancer Research Fund . And scientists at Harvard Medical School have found that women who drink three or more cups of coffee a day have a 20 per cent lower risk of developing the most common form of skin cancer compared to those who had less than one cup per month . They also found that men who drank the same amount saw a nine per cent lower risk of the skin cancer , basal cell carcinoma .
Coffee can stop cancer returning in patients treated with tamoxifen . insulin stops oestrogen reaching cancer cells , so they do not grow . older patients had fewer tumors and their tumours were smaller . Caffeine cuts of signalling pathways that the cancer cells require to grow .