Nature 258, 171 - 173 (13 November 1975); doi:10.1038/258171a0

Inability of the cat to desaturate essential fatty acids

J. P. W. RIVERS, A. J. SINCLAIR & M. A. CRAWFORD

Nuffield Institute of Comparative Medicine, Zoological Society of London, Regent's Park, London NW1 4RY, UK

MOST vertebrate species require some dietary source of essential fatty acids (EFAs)^1,2. A wide range of naturally occurring polyunsaturated fatty acids have been shown to exhibit EFA activity, but they can be classified into two homologous series characterised by the position of the terminal double bonds relative to the methyl (omega) carbon atom. The 6 series of EFAs all have double bonds in the 6 and 9 positions, the 3 series in the 3, 6 and 9 positions. The metabolic interrelationships of the members of each series are shown in Fig. 1. The naturally occurring 18-carbon parent compounds for each series are linoleic acid (18:2 6) and linolenic acid (18:3 3) and EFA requirements are usually stated in terms of either or both ot these parent EFAs (p-EFAs)^1,3.

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