Eating processed meat, such as sausage, ham, and bacon, but not red meat, on a regular basis is associated with a significantly increased risk of breast cancer, a review study suggests.
The study, “Consumption of red and processed meat and breast cancer incidence: A systematic review and meta‐analysis of prospective studies,” was published in the International Journal of Cancer.
Processed meat refers to meat that has been smoked, cured, salted, or processed in another way to enhance flavor or extend its shelf life.
The World Health Organization has warned that consuming processed meat can increase the risk of cancer, particularly colorectal cancer, while it has referred to red meat as probably carcinogenic.
Several studies have linked the consumption of processed and red meat with multiple cancers, including breast cancer, but others have found no association between them.
Researchers have now reviewed all studies published before January 2018 that evaluated the association between eating processed and red meats and the occurrence of breast cancer.
They analyzed the results of 15 studies evaluating the association between processed meat and breast cancer incidence, which included data from 37,070 breast cancer cases in more than 1.2 million women.
Results showed that women eating the highest amount of processed meat (about 25-30 grams a day, on average) had a 9% higher risk of developing breast cancer than those who ate the lowest amount (a median of 0-2 grams per day).
According to the researchers, the high amounts of nitrates or nitrites — which can lead to the formation of potentially carcinogenic chemicals — saturated fat, cholesterol, and animal-derived iron have been suggested as the reason why processed meat may raise the risk of cancer, including breast cancer.
Analyzed results of the studies, however, showed no significant association between red (unprocessed) meat consumption and the risk of breast cancer.
Looking at other breast cancer risk factors, such as menopausal or hormone receptor status, or distinct activity levels of an enzyme thought to protect against the carcinogenic effects of meat, the team only found a significant link between higher consumption of processed meat and a higher risk of breast cancer after menopause, but not before menopause.
The researchers noted that the absence of a statistically significant link in premenopausal women may be due to a smaller sample size, and further studies should be conducted to clarify this.
“Previous works linked increased risk of some types of cancer to higher processed meat intake, and this recent meta-analysis suggests that processed meat consumption may also increase breast cancer risk,” Maryam Farvid, the study’s lead author and a researcher at Harvard T.H. Chan School of Public Health, said in a press release. “Therefore, cutting down processed meat seems beneficial for the prevention of breast cancer.”
The researchers admitted, however, that their study has some limitations due to some variability among studies, and that since most of the studies were conducted in North America and Europe, the findings may not be generalized to women in other regions of the world.