Essential fatty acids and prostaglandins.

The World Health Organization's recommendation for dietary intake of essential fatty acids is 3% of energy (en%) of linoleate. Evidence from rat studies suggests that more than 3 en% is desirable for the regulation of eicosanoid metabolism. With such a low level of available linoleate, humans tend to synthesize more prostanoids than they do with 6% or more energy from linoleate. High rates of prostanoid synthesis probably are deleterious, so that the lower rate commensurate with 6-12 en% of linoleate probably is desirable. The amount of linoleate needed for normal function is influenced by the dietary content of other fatty acids, particularly saturated fats and those of the n-3 family. Vitamin E is necessary for normal metabolism of polyunsaturated fatty acids. In a diet providing sufficient available total energy with 30% as fat, the lower range of linoleate (6-8 en%) probably is sufficient if the saturated fatty acid content is 10% or less. With a greater proportion of saturated fatty acids, more linoleate is needed to maintain a polyunsaturated to saturated fatty acid ratio of 0.7 to 1.0. Some n-3 fatty acids probably are required, and more than a minimal amount may be beneficial. Current recommendations are for 0.5-1.0 en% in a diet containing 5-6 en% of linoleate.