Effect of three intravenously administered fat emulsions containing different concentrations of fatty acids on the plasma fatty acid composition of premature infants

The effects of an intravenously administered lipid emulsion supplemented with γ-linolenic acid on the fatty acid profile of premature infants were compared with those of two conventional lipid emulsions. Fifty-nine premature neonates receiving total parenteral nutrition were randomly assigned to receive either fat emulsion containing γ-linolenic acid and long-chain triglycerides (LCT), an LCT emulsion, or a 50% (wt/wt) mixture of medium-chain triglycerides and LCT emulsion. Forty-nine infants completed the study. During the 6-day study there was a significant tenfold increase in the plasma levels of γ-linoleic acid in the supplemented group versus the other two groups. A significant threefold to fivefold increase in the ω6 long-chain polyunsaturated fatty acids was observed in all groups. These changes seemed to be attributable mostly to linoleic acid from the lipid emulsion, despite the 50% lower dose in the medium- and long-chain triglycerides group. The increase in the ω3 long-chain polyunsaturated fatty acids also was mainly caused by a similar increase in the level of α-linolenic acid. No differences were recorded in the linoleic/α-linolenic acid ratio among the groups. Plasma levels of some of the semiessential fatty acids were significantly higher in the medium- and long-chain triglycerides group than in the LCT group. This may be related to slower elimination of LCT, to the difference between emulsions, or to less substrate inhibition on Δ-6-desaturase, which seems to be less of a rate-limiting enzyme than previously considered. Further intravenous feeding trials are needed to identify the optimal balance of fatty acids for nutrition of these premature infants. (J PEDIATR 1994;125:596-602).