Processed meat has long been linked to other cancers of the pancreas, prostate and bowels, but this study is the first to show a link with tumors that start in the breast.
Women who consumed the most processed meat were nine percent more likely to develop the disease, according to a meta-analysis of data from 28 previous studies.
They found no elevated risk for those who ate unprocessed red meat such as beef, lamb, pork, veal, goat and mutton.
The World Cancer Research Fund recommends cutting out red meat altogether, but the NHS says that those who cannot should try to stick to a limit of 70g a day (the equivalent of half a burger or one sausage).
This new research by Harvard offers another reason for women to keep cutting it out: it could impact their cancer risk.