Adolescent girls who eat more plant-based compounds that mimic the female hormone estrogen may reduce their chances of developing breast cancer later in life.
These compounds, known as phytoestrogens, are found in foods such as tofu, fresh fruit and vegetables, flax and wholegrain bread.
Dr. Michelle Cotterchio of the University of Toronto and her colleagues asked more than 3,000 recently diagnosed breast cancer patients about their diets as teenagers, and compared their responses with those from a similar number of healthy women.
The researchers then divided the women into four groups depending on whether they had very low, low, medium or high intake of phytoestrogens as teenagers. These categories took into account the phytoestrogen content of different foods, and whether women had consumed these foods daily, weekly, monthly or not at all.
The higher a woman’s phytoestrogen intake during adolescence, the lower the likelihood that she had breast cancer.
Compared with women who ate little or no phytoestrogen-containing foods as teenagers, those who had a low intake had a nine per cent reduced breast cancer risk, those who ate moderate amounts had a 14 per cent reduced risk, and those in the high-intake category had a 29 per cent reduced risk.
The study focused on the two main classes of phytoestrogens: isoflavones, which are found in soybeans and soy products such as tofu, and lignans, which are found in whole grains, fruit, vegetables, teas and coffees.
Cotterchio says her findings, if confirmed, have important implications for breast cancer prevention because diet is a potentially modifiable risk factor. “But right now, any dietary recommendations would be premature.”
She and her colleagues are also looking at the association between phytoestrogen intake in adulthood and breast cancer risk. “Adolescent exposure may be more relevant because that’s when breast tissue is rapidly developing.”