Effect of a low-fat diet on hormone levels in women with cystic breast disease. I. Serum steroids and gonadotropins.

For examination of the effect of a low-fat diet on serum estrogen, progesterone, and gonadotropin levels, 16 patients with cystic breast disease and cyclic mastalgia were studied before dietary intervention and at 2 and 3 months thereafter. Four-day food diaries indicated that total fat intake was reduced from a prediet average of 69 g (35% of total kilocalories/day) to an average of 32 g (21% of total kilocalories) after 3 months. Highly significant reductions (P less than .001) occurred in dietary cholesterol and less changes occurred in protein and total kilocalorie consumption (P less than .05); fiber intakes were not affected. After 3 months on this low-fat diet, there were significant reductions in luteal-phase serum total estrogens (P less than .001), estrone (P less than .005), and estradiol (P less than .01); progesterone, luteinizing hormone, and follicle-stimulating hormone levels were unchanged. Two of the 16 patients were excluded from the hormone statistical analyses because the serum progesterone levels were not consistent with sampling in the luteal phase of the menstrual cycle. It is concluded that a reduction of dietary fat intake to 20% of the total kilocalories will result in significant decreases in circulating estrogens in benign breast disease patients and that this effect is achievable without increasing dietary fiber consumption. Absence of changes in serum progesterone and gonadotropins during the dietary intervention is consistent with altered enterohepatic circulation of estrogens rather than with effects on the pituitary-ovarian axis.