The incidence of breast cancer has been rising steadily, most quickly in rich countries. In 1997, around the world, close to 400,000 women died of the disease.
By Dennis Bueckert | The Canadian Press
Ottawa - Consumption of hormone-treated beef may be causing girls to reach puberty earlier than they used to and making them more susceptible to breast cancer, say researchers attending a world conference on breast cancer.
It is "very likely" that hormone residues in North American beef is a factor in the early onset of puberty among girls in recent decades, said Carlos Sonnenschein of the Tufts University School of Medicine at Boston.
"There is no other reason to explain it," Sonnenschein said in an interview Friday.
Pediatricians say the onset of menstruation has steadily decreased in recent decades. The average age for a first period is now 12, up from age 14 in 1900.
Early onset of puberty with its raging hormones translates into higher risk of breast cancer, said Sonnenschein.
"The length and amount of exposure to estrogens (a class of hormones) is one of the most significant risk factors in breast carcinogenesis.
"Unless you are exposed to estrogens you don't get breast cancer. The longer the exposure is, the higher the incidence. Therefore if you decrease the age of menarche (first menstruation) ... you are at higher risk."
Hormones are used by cattle farmers in Canada and the United States to increase the weight of cattle prior to slaughter. They are currently the focus of a major trade dispute between North American and the European Union.
Annie Sasco, of the International Agency for Research on Cancer at Lyons, France, said more study is needed but it makes sense that hormone-treated beef could affect the onset of puberty.
"Any exposure to a high level of hormones is associated with earlier onset of puberty. It needs to be studied more but it makes sense."
She said the risk of breast cancer associated with hormone residues in meat is not proven, and is probably small.
"We all have estrogens and we need estrogens," she told the mainly female audience. "They are needed for life, for being what we are. We cannot say, 'Ban estrogens.'
"We all have to try, through our diet and physical exercise, to keep our levels down. But there is a need to keep things in perspective ... without getting into a complete panic."
Even if the risk is small, she said it would be prudent to stop the use of hormones in the cattle industry there's no offsetting health benefit for consumers.
The European Union has banned the use of hormones for fear they pose a health risk, and has banned imports of hormone-treated Canadian and U.S. meat.
The two North American countries have taken the dispute to the World Trade Organization and have won the right to retaliate by placing tariffs on European goods. Canada announced retaliatory tariffs on a range of goods this week.
The federal government maintains the hormones are safe, despite strong misgivings on the part of its own scientists at the Health Protection Branch.
Four scientists with concerns have been placed under orders not to discuss the issue in public.
The incidence of breast cancer has been rising steadily, most quickly in rich countries. In 1997, around the world, close to 400,000 women died of the disease.
The number of new cases reported annually approached 900,000 in 1997, up from 572,000 in 1980.
