Diet and female sex hormone concentrations: an intervention study for the type of fat consumed. A possible mechanism by which dietary fat may influence the development of breast cancer is by influencing the concentration of female sex hormones. This study investigated the effect of alteration in the type of fat consumed on concentrations of female sex hormones in serum. Female volunteers were randomly assigned to continue on their usual meat-eating diet, change to a vegetarian diet, or change to a diet that was predominantly vegetarian but where fish was consumed at least three times per week. Change to the vegetarian or fish diet had little effect on diet total hormone concentrations; however, the amount of estradiol was significantly decreased in the vegetarian group. When nutrient consumption was correlated with hormone concentrations, prolactin was directly associate with fat consumption, sex-hormone-binding globulin was inversely associated with fat consumption (particularly cholesterol consumption), and the proportion of nonprotein-bound estradiol was directly associated with complex carbohydrate consumption. 