Burgers may increase a woman’s risk of breast cancer, new Harvard research suggests.
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). The US does not recommend a specific limit.
The amount of processed meat in the American diet has dropped in recent years, but millions still easily exceed the proposed 70g limit.
This new research by Harvard offers another reason for women to keep cutting it out: it could impact their cancer risk.
The increased risk is modest at nine percent, but the researchers say any increase is significant.
Processed meat is meat that has been salted, cured, fermented, smoked or blended to make sausages, hot dogs, salami, bacon, ham and corned beef.
Scientists pooled data from 28 previous studies and found those who ate more than this were more prone to breast cancer.
Processed meats have previously been linked to fueling bowel, prostate and pancreatic tumors.
Lead author Dr Maryam Farvid, of the Harvard T.H. Chan School of Public Health, said: ‘Previous works linked increased risk of some types of cancer to higher processed meat intake.
‘This recent meta-analysis suggests that processed meat consumption may also increase breast cancer risk.
‘Therefore, cutting down processed meat seems beneficial for the prevention of breast cancer.’
The study published in the International Journal of Cancer analysed all published studies on the topic.
It included 13 studies on red meat that included a total of 1,133,110 women, 33,493 of whom developed breast cancer, and 15 on processed meat involving 1,254,452 women, 37,070 of whom were diagnosed with the disease.
Diet was generally assessed by food frequency questionnaire.
Research Scientist Dr Farvid and colleagues said processed meat consumption was associated with a nine percent higher breast cancer risk.
No significant association was observed between red, or unprocessed, meat intake and risk of the disease.
Food additives nitrate and nitrite that give processed meats their pink color may be to blame – along with the saturated fat, cholesterol and a type of iron that comes from animal proteins.
Dr Farvid said: ‘Although high amounts of nitrate and nitrite might link processed meat to increased risk of breast cancer, the high content of saturated fat, cholesterol and heme iron found in red meat may also underlie the association with breast cancer.
‘This systematic review and meta-analysis including prospective cohort studies of red meat and processed meat consumption provides evidence that higher consumption of processed meat is associated with higher risk of breast cancer.
‘However, red meat was not a significant cause of breast cancer.’
She said globally, breast cancer is the most common cancer among women and the second leading cause of cancer death.
But prior studies on red and processed meat consumption with breast cancer risk have generated inconsistent results.
Dr Farvid said: ‘Given the international variations in breast cancer rates and trends, the importance of identifying modifiable lifestyle risk factors is widely acknowledged as a means to reduce breast cancer.
‘Red meat is hypothesised to be an important dietary risk factor for several cancer sites, and provides a source of animal fat, heme iron and chemical carcinogens that may accumulate during cooking and/or processing.’
The International Agency for Research on Cancer (IARC) concluded that consumption of red meat was a probable human carcinogen, whereas processed meat was classified as ‘carcinogenic to humans.’
This classification was largely based on the evidence for colorectal, pancreas and prostate cancers for red meat and colorectal, or bowel, cancer for processed meat.
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