Eating red meat significantly increases a post-menopausal woman's chance of breast cancer, research suggests.
A University of Leeds team monitored 35,000 women over seven years.
Older women who ate one 2oz portion a day (57 grams) had a 56% increased risk compared with those who ate none, the British Journal of Cancer reports.
And those who ate the most processed meat, such as bacon, sausages, ham or pies, had a 64% greater risk of breast cancer than those who refrained.
However, experts warned it was extremely difficult to pin down the effect of specific parts of the diet on cancer risk, and said previous research had produced inconclusive results.
Lead researcher Professor Janet Cade said younger, pre-menopausal women who ate large amounts of red and processed meat also had a raised risk of breast cancer - but the effect was not statistically significant.
Saturated fats
Professor Cade said: "Meat is high in saturated fat, and saturated fat influences the amount of cholesterol the body makes. Cholesterol is precursor to oestrogen, which has been linked to an increased risk of breast cancer.
"Cooking meat at high temperatures might also form carcinogenic compounds.
"My advice to women who are consuming relatively high amounts of red and processed meat on a daily basis is to consider reducing their intake."
Earlier findings from the same study showed that pre-menopausal women who have the greatest intake of fibre have cut their risk of breast cancer in half.
Diet a factor
Dr Alexis Willett, of the charity Breakthrough Breast Cancer, said: "This is an interesting study but because we eat a variety of foods it is difficult to separate out the specific effect of red meat on breast cancer risk.
"Differences in other factors such as age, weight and level of exercise were also found between red meat eaters and non-red meat eaters in this study and may also play a part in the risk of developing breast cancer.
"Previous research studying red meat and breast cancer risk have been inconclusive.
"However, experts estimate that approximately 30% of all cancers in Western countries are linked to diet."
Henry Scowcroft, of Cancer Research UK, said women should maintain a healthy body weight, take regular exercise, and avoid regular portions of fatty foods like red and processed meat.
A US study published in November found eating large amounts of red meat might double young women's breast cancer risk.
The Archives of Internal Medicine study looked at over 90,000 pre-menopausal women.
Having one-and-a-half servings of red meat per day almost doubled the risk of hormone receptor-positive breast cancer compared to three or fewer per week.
However, UK cancer experts said animals in the UK were not given growth hormones which are used for US animals.
