The effect of a low-fat diet on luteal-phase prolactin and oestradiol concentrations and erythrocyte phospholipids in normal premenopausal women.

1. Fifteen normal premenopausal women followed a low-fat diet for a period of 2 months. 2. Daily fat intake was reduced from 81 g on their customary diet to 36 g on the low-fat diet. A significant reduction in total energy intake and an increase in the dietary polyunsaturated fat: saturated fat ratio was also observed. There was a significant decline in body-weight, percentage body fat and total serum cholesterol, but no significant change in high-density-lipoprotein-cholesterol. 3. Luteal-phase prolactin concentrations were not altered, but there was a significant decline in oestradiol concentrations on the low-fat diet. The proportion of erythrocyte inositol-phospholipid was increased on the low-fat diet and there was a significant increase in the 20:4 omega 6 (arachidonate) content of inositol-phospholipids. No significant changes in the content or fatty acid compositions of other phospholipid fractions were observed. 4. Further investigation of the effect of level and type of dietary fat on the content and fatty acid composition of membrane inositol-phospholipids are required. Long-term studies investigating the response of both prolactin and oestradiol to dietary fat reduction are also warranted.