Dietary linolenic acid in man--an overview

Small amounts of linolenic acid are ubiquitous in human food but only a few foodstuffs contain sizable amounts, namely some plant oils, butter and fish; in marine fish, linolenic acid is accomplished by eicosapaentaenoic acid, highly exceeding linolenic acid in quantity. Of the linolenic acid ingested, some is incorporated into phospholipids and cholesteryl esters, very little is elongated and eventually converted to prostaglandins; probably most linolenic acid is used as fuel. Polyunsaturated fatty acids of the (n-3)-series should no longer be considered to be similar with respect to their metabolic fate and their effects. In particular, results from experiments with "eskimo diets" may not be applied to considerations of linolenic acid. There may be a small dietary requirement for linolenic acid, possibly only for growing children; yet it is prudent to recommend diets which are not devoid of linolenic acid, especially in formula diets or parenteral nutrition. Some experiments suggest that high doses of linolenic acid exert untoward effects by inhibiting prostaglandin synthesis of the 1- and 2-series. The ratio between linoleic and linolenic acid in relevant experiments was such that only excessive use of linseed oil could produce them under conventional dietary conditions. Still it must be considered prudent to keep the linolenic acid content of foods well below that of linoleic acid.