Composition of phospholipid fatty acids in red blood cell membranes of patients in intensive care units: effects of different intakes of soybean oil, medium-chain triglycerides, and black-currant seed oil.

Fatty acid composition of phospholipids in red blood cell membranes was studied in 32 severely head-injured or cerebral stroke patients receiving enteral nutrition for 3 weeks. During this study the effects of three diets differing only by their lipid composition were investigated. The daily energy intake of each patient amounted to 2950 kilocalories, of which the lipid fraction represented 45.7%. Diet A contained only soybean oil, diet B consisted of a 50% soybean oil and 50% medium-chain triglycerides mixture, and diet C was an emulsion of 50% soybean oil, 42.5% medium-chain triglycerides, and 7.5% black-currant seed oil. Our results showed no biochemical signs of fatty acid deficiency in red blood cell membranes for the patients at the beginning of the study, after a comparison with a control group of 20 healthy adults. Inhibition of delta 6-desaturase activity on linoleic acid (C18:2 omega 6) after diet A was suggested by an increase of linoleic acid without a corresponding increase of dihomo-gamma-linolenic acid (C20:3 omega 6). Replacing 50% of soybean oil by with medium-chain triglycerides (diet B) prevented this enzyme inhibition. Supply of black-currant seed oil rich in gamma-linolenic (C18:3 omega 6) and stearidonic (C18:4 omega 3) acids (diet C) induced significant increases of dihomo-gamma-linolenic and eicosapentaenoic (C20:5 omega 3) acids, without influencing arachidonic acid (C20:4 omega 6) levels. This balance was evaluated through the ratio (C20:3 omega 6 + C20:5 omega 3)/C20:4 omega 6.