Lipid emulsions contain not only triglyceride (TG)-rich particles but also phospholipid (PL)-rich particles that are believed to trap free cholesterol and apoprotein E, when they are infused in excess. The present study was designed to evaluate the effects of such abnormal PL-rich particles on lipid metabolism during a 5-day infusion in man. Eighteen patients undergoing esophagectomy were evenly randomized to receive intravenously during 5 days 1.75 g.kg-1.d-1 long-chain TG from either a 10% lipid emulsion with a PL/TG weight ratio of 0.12 (group A), a 10% emulsion with a PL/TG weight ratio of 0.06 (group B), or a 20% emulsion with a PL/TG weight ratio of 0.06 (group C). Plasma PL, free cholesterol, and apoprotein E increased progressively in group A (4.1 +/- 0.3 mmol/L, 2.4 +/- 0.3 mmol/L, and 0.089 +/- 0.012 g/L on day 5, respectively) but not in groups B (2.7 +/- 0.3 mmol/L, 1.3 +/- 0.2 mmol/L, and 0.048 +/- 0.007 g/L) and C (2.4 +/- 0.2 mmol/L, 1.2 +/- 0.1 mmol/L, and 0.050 +/- 0.006 g/L). Free fatty acids and TGs remained constant and similar in each group postoperatively. After fat infusion had been stopped at the end of the fifth day, the elimination of plasma TGs over the next 4 hours was comparable in the three groups. We conclude that excess egg PLs induce alterations of plasma lipids even within a few days.