Polyunsaturated fatty acid supply with human milk. Physiological aspects and in vivo studies of metabolism.

The origin of polyunsaturated fatty acids (PUFA) in human milk has not been studied in detail. Diet, liberation from maternal stores and endogenous synthesis from precursors may contribute to PUFA present in human milk. Other factors influencing lipid content and fatty acid composition such as gestational age, stage of lactation, nutritional status and genetical background are known. In a series of in vivo studies using stable isotope methodologies we investigated the metabolism of PUFA during lactation. With this techniques the transfer of single dietary fatty acids into human milk, the oxidation and the deposition in tissues were estimated. Our studies demonstrate that the major part of PUFA in human milk seems not to be derived directly from the maternal diet but from body stores. Nevertheless diet is important, because long term intakes affect composition of body stores.