Daily consumption of red meat might may significantly increase a woman’s risk of certain breast cancers, even before she reaches menopause, according to a new study.

Women who ate large amounts of red meat were more than twice as likely to suffer hormone-related breast cancer, researchers found. Chemicals added during meat processing or growth hormones given to cattle may be to blame, they speculate.

Eunyoung Cho of the Harvard Medical School in Boston, Massachusetts, US, and colleagues followed more than 90,000 women aged 26 to 46 from 1991 to 2003 as part of a large, ongoing nurses’ health study. Every four years, participants were asked about their diet and medical history, including whether or not they had experienced breast cancer and what type.

Over the course of the study, more than 1000 women developed breast cancer. Of those, 512 were cancers that were sensitive to the hormones oestrogen and progesterone. Another 167 were hormone-insensitive cancers, and the remaining 342 cancers were of mixed or unknown status.


Middle-aged women

Women in the study who ate more than 1.5 servings of red meat per day had nearly double the risk of developing hormone-sensitive breast cancer as those who ate three or fewer servings per week, the team found. A single serving equates to a quarter-pound hamburger, for example, or 100 grams of red meat.

The hormones or hormone-like compounds in red meat may promote the growth of hormone-sensitive breast cancer by attaching to specific hormone receptors on the tumours, Cho suggests.

She notes that hormone sensitive cancers are increasingly common in the US – particularly among middle-aged women – while the rate of hormone insensitive cancers has remained relatively stable. The chances that women between the ages of 40 and 49 years would develop oestrogen-sensitive breast cancer in 1992 was 65 in 100,000, but it increased to 75 in 100,000 by 1998. This might be because women are consuming more foods that contain added hormones or hormone-like compounds than they used to in previous decades, Cho says.

Small risk

While few studies have looked at the link between red meat intake and breast cancer in young women, earlier studies have found a possible link in older women. And red meat consumption has been suggested as a cause of other tumour types, such as bowel cancer.

Cho adds that since red meat also contains saturated fat, “it’s prudent for women to reduce their red meat intake for health purposes”.

But other experts say that women should not feel greatly alarmed by the new findings.

“The overall risk of pre-menopausal breast cancer is low when compared to getting the disease after the menopause. So even at the highest rates of meat consumption, this is overall still a relatively small increase,” says Henry Scowcroft at Cancer Research UK.

Journal reference: Archives of Internal Medicine (vol 166, p 2253-2259, 2006)