Effect of high-fat intake on lactogenic hormone bioactivity in premenopausal women

To determine if dietary fat affects the bioactivity of circulating prolactin and growth hormone (lactogenic hormones), a controlled feeding study was conducted in six premenopausal women over two complete menstrual cycles. After an initial 7-10 d dietary adjustment, subjects were randomly assigned to either low-fat (25% of calories) or high-fat (46%) diets. The diets were similar in proportions of energy, protein, P:S ratio, and cholesterol. All subjects completed both diets in a crossover experimental design. Fasting blood samples were collected on alternate days throughout the study. Plasma hormone bioactivity was assayed by the Nb2 lymphoma cell method. Luteal-phase lactogenic hormone bioactivity appeared to be higher (averaging 28%; p less than 0.07) in response to high- rather than low-fat diets. No differences were seen in levels of radioimmunoreactive prolactin or growth hormone. Substantial changes in short-term fat intake may alter the level of lactogenic hormone bioactivity in young women.