No link found between iron and breast cancer

NEW YORK (Reuters Health) - While some prior research has hinted at a link between meat consumption and breast cancer, a large new study suggests that the iron in meat is probably not to blame.

“Breast cancer rates are highest in countries with a high standard of living and a high consumption of meat,” lead researcher Dr. Geoffrey Kabat of Albert Einstein College of Medicine, New York City, told Reuters Health in an e-mail.

Meat’s saturated fat has been the focus of many of the studies that have tentatively tied meat to the cancer. “But little attention has been devoted to intake of iron in the diet and particularly heme iron, the major form of iron present in meat,” said Kabat, noting that iron can cause oxidative damage to DNA, potentially leading to an increased risk of cancer.

Kabat and his colleagues studied 116,674 postmenopausal women who participated in the National Institutes of Health-AARP Diet and Health Study, looking for any evidence of a link between amounts of iron in the women’s diets and their risk of developing breast cancer, the leading cancer among women worldwide.

Each participant filled out a detailed survey that included not only all foods consumed, but also specific types of meats, how they were prepared and levels of doneness -- all of which may affect the meat’s iron content.

During the course of the six-and-a-half-year study, 3,396 of the women were diagnosed with breast cancer, report the researchers in the American Journal of Clinical Nutrition.

After accounting for various other factors that could be associated with breast cancer -- including age, obesity, family history, smoking, use of hormone therapy and physical activity -- the team found no link between breast cancer and any form of dietary iron.

The researchers distinguished between all dietary iron, including that from vegetable and grain sources; iron from all meats, including chicken and bacon as well as red meat; and iron from red meat only, and still found no apparent connections to breast cancers.

The authors did note a few limitations in their study. For example, they had incomplete information on the women’s intake of iron via supplements and no data on their iron consumption earlier in life, such as during adolescence when breast tissue is developing.

Despite much research into the role of meats and other elements of women’s diets, the results have not consistently shown any links, the authors note.

“Decades of research have not identified any strong effects of diet as assessed in adulthood on the risk of breast cancer,” said Kabat.

“From what we know,” he added, “eating a varied diet, maintaining a healthy body weight, and engaging in physical activity are the most important things one can do, in terms of lifestyle, to reduce one’s risk of breast cancer.”

SOURCE: American Journal of Clinical Nutrition, online October 20, 2010.