The decade-long study, which included more than 71,000 women aged 40 to 69, showed that women who ate processed meat at least once a week were 57% more likely to develop breast cancer than those who avoided it, with the effect being strongest among women under 50.
Researchers believe the culprit lies in sodium nitrite, a common preservative in processed meats. It can convert inside the body into carcinogenic compounds that affect DNA and increase the likelihood of mutations in breast tissue. This substance is used to kill bacteria, improve flavor, and keep meat pink for longer.
The researchers confirmed that unprocessed meats, such as fresh chicken and beef, did not show a clear link to an increased risk of breast cancer.
For its part, the Anti-Nitrite Alliance UK campaign group said: "This is further evidence linking processed meat to cancer. Families should not be exposed to substances that may form carcinogenic compounds without their knowledge. The government must take action to remove nitrites from the food chain, especially since there are safer alternatives."
These findings confirm warnings from the World Health Organization's International Agency for Research on Cancer, which classifies processed meat as a Group 1 carcinogen, the same category that includes tobacco, asbestos, hepatitis B, and arsenic.
Experts have indicated that genetic factors play a role in breast cancer, but other factors such as diet, alcohol consumption, smoking, and obesity are becoming increasingly important.
The study was published in the journal Clinical Nutrition.
