A modest reduction in fat intake during puberty is associated with changes in the levels of certain sex hormones, according to a study of adolescent girls in the January 15 issue of the Journal of the National Cancer Institute. In adults, elevated levels of sex hormones are associated with an increase in breast cancer risk.
Joanne F. Dorgan, Ph.D., of the Fox Chase Cancer Center in Philadelphia, and her colleagues conducted a study ancillary to the Dietary Intervention Study in Children to examine whether diet influences sex hormone levels during adolescence. The study involved 286 girls ages 8 to 10 who were randomly assigned to a low-fat dietary intervention group or to a group receiving usual care (e.g., educational materials available to the public). The researchers measured blood sex hormone levels at the start of the study and 1, 3, 5, and 7 years later.
After 5 years, girls in the intervention group had 29.8% lower estradiol, 30.2% lower non-sex hormone binding globulin-bound estradiol, 20.7% lower estrone, and 28.7% lower estrone sulfate levels during the first half of their menstrual cycles and 27.2% higher testosterone levels during the second half of their menstrual cycles compared with girls in the usual care group. After 7 years, girls in the intervention group had half the progesterone levels during the second half of their menstrual cycles as did girls in the usual care group.
Girls in the intervention group reported consuming less total and saturated fat overall than girls in the usual care group. Girls in the intervention group also reported consuming more dietary fiber.
Although their study found that a low-fat diet resulted in reductions in estrogen hormone concentrations, the authors say that "whether these differences ultimately influence breast cancer risk is unknown." A parallel study was conducted in boys, and results will be reported separately.
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