"The risk of early menarche for girls who consumed more than 25 grams of dietary fibre a day [in the form of cereals, whole grains, vegetables and fruit] was approximately half that of girls who had less than 18 grams of fibre a day," says Malcolm Koo, a professor in public health sciences at U of T.
For his doctoral thesis, Koo studied the role of dietary fibre and its link to the onset of menstruation. The study, which took place from 1992 to 1996, involved 637 pre-menstrual girls in Ontario between the ages of six and 14. Information on dietary intake, physical activity, maternal history and date of menarche was collected. In the study, the age of menstrual onset ranged from 8.5 to 15.6 years with a median age of 13.6.
Estrogen, a hormone that develops and maintains female characteristics, is known to bind with fibre in the body, Koo says. Girls with higher fibre diets may be expelling more estrogen which correlates with later onset of menarche. As part of his research, Koo also found that girls who consume higher amounts of monounsaturated fats in their diet (such as olive and canola oil) also experience later onset of menarche.
Early menarche (for girls 12 and under) correlates to a 10 to 15 per cent higher risk of breast cancer later in life. Evidence suggests that women who have been menstruating longer have increased breast tissue exposure to estrogen, which is linked to an increased risk of developing breast cancer. The study was recently published in Public Health Nutrition and funded by the National Cancer Institute of Canada.