Breast cancer is the most common type of cancer in women globally, and researchers at South Korea's National Cancer Center conducted a prospective cohort study to investigate how dietary factors — including dietary habits and the types of food consumed — influence breast cancer risk in Korean women.
They recruited women aged 30 and above from the National Cancer Center between August 2002 and May 2007, monitoring them until December 2014 with the aid of the Korea Central Cancer Registry, which identified breast cancer cases.
Subsequently, 72 breast cancer cases were identified from among 5,046 women who had not been previously diagnosed.
The researchers noted that compared with the healthy participants, those with breast cancer tended to be more highly educated (58.3% had attained college education or higher, compared to 39.5% of the non-cases), former or current smokers (22.2% of patients versus 7.8% of healthy subjects), and were likelier to have had a history of benign breast tumours (10% versus 4%).
In addition, the researchers wrote that the "consumption of grilled meat conferred a significantly higher risk of breast cancer in all women and in postmenopausal women".
Intake of high-cholesterol food and irregular meals were also linked to higher breast cancer risk for all women, including premenopausal women; the association between dietary cholesterol and breast cancer risk, however, was unclear due to inconsistent results.
Meat versus mammaries
The direct association between breast cancer risk and grilled meat consumption was hypothesised as the result of carcinogenic mutagens such as heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs), which are present in large amounts in meat cooked at high temperatures, particularly barbecued or grilled meat.
Creatinine, amino acids and sugars in meat muscles react at high temperatures to form HCAs, while meat cooked directly over an open flame results in PAHs being produced on or near the meat’s surface; grilled food consumption is said to be one of the most common culprits behind female exposure to PAHs.
In postmenopausal women, the association may be explained by differences in oestrogen metabolism pathways related to menopausal status. Ovaries are a woman's major oestrogen sites before menopause, but after menopause, adipose tissue is vital in synthesising oestrogen.
However, the researchers said "the mechanisms of the association between menopausal status and breast cancer and the interactions with diet remain unclear".
They concluded: "Further studies with longer follow-up periods that include information on portion size, hormone receptor status, levels of each carcinogen in grilled meat, and classification of food groups by the source are needed."
"Dietary Factors and Female Breast Cancer Risk: A Prospective Cohort Study"
Authors: Ji Hyun Kim, et al.