In vivo conversion of linoleic acid to arachidonic acid in human adults

Human adults are shown to be capable of conversion of linoleic acid (LA, 18 .2 n-6) to arachidonic acid (AA, 20:4 n-6) in vivo. It is confirmed that th ey can also convert alpha-linolenic acid (LNA, 18:3 n-3) to eicosapentaenoi c acid (EPA, 20:5 n-3) and to docosahexaenoic acid (DHA, 22:6 n-3) in vivo. The time course and the maximal response for these processes during the fi rst week after a single dose of the 18-carbon precursor is described. A sta ble-isotope method in which the protons of the C17 and C18 carbons are subs tituted with deuterium atoms is used in order to provide for a safe method for the study of human metabolism. High sensitivity and selectivity of dete ction is assured with negative ion, gas chromatography/mass spectrometry an alysis. It is clear that human adults on an ad lib diet carry out EFA metab olism in vivo.