['Endothelial function as determined by flow-mediated dilation (FMD) deteriorates during postprandial lipemia. The impairment can be neutralized by adding 50 g casein to the fatty meal. The objective of this study was to see which of the casein constituents is responsible for this neutralization effect.', 'A crossover design was used in 15 healthy volunteers, who were given 3 ml cream/kg body weight with and without 2.5 g L-arginine. Lipids and FMD were then determined hourly over a period of 6h. In substudies this design was repeated with 2.5 g phenylalanine and 5 g leucine in 11 subjects. The effect of 2.5 g L-arginine on FMD in the absence of cream was tested in seven subjects.', 'Without L-arginine the FMD deteriorated during 4h after the fat loading. Addition of L-arginine prevented this deterioration at 3 and 4h. Phenylalanine and leucine, in contrast, did not prevent the lipemic endothelial dysfunction. L-Arginine alone similarly had no acute effect on the FMD.'] Does addition of 2.5 g L-arginine in a fatty meal prevent the lipemia-induced endothelial dysfunction in healthy volunteers?