The offspring of rats that took folic acid supplements before conception, during pregnancy and while breast-feeding have breast cancer rates twice as high as other rats, says a new study.
They also had more tumours and developed them at a faster rate, according to the study led by Dr. Young-in Kim, a gastroenterologist at St. Michael's Hospital in Toronto.
Kim stressed more research needs to be done to determine whether the findings also apply to humans. While there are similarities in breast cancer in rats and humans, there are differences in how rats and human metabolize folic acid.
A diet rich in natural folate, found in grains and dark, leafy vegetables, may help prevent cancer. But Kim's study adds to a growing body of evidence that high folate intake through supplements may promote some cancers-and prevent others.
In Kim's animal study, half the rats were given folic acid supplements-equivalent to what pregnant women in North America take in addition to the mandatory fortification in some foods - three weeks before mating and throughout the pregnancy and lactation. After weaning, half the female pups received the same amount of folic acid supplement as the pregnant rats.
Both the rats whose mothers took folic acid supplements and those who ate a folic acid supplemented diet had a twofold increase in rates of mammary tumours than the control groups. They also had more tumors and faster-growing tumors.
The study has been published in the journal Cancer Research.