Effects of Whey Protein and Casein on the Plasma and Liver Lipids in Rats

The effects of whey protein and casein (both as a 25% diet) on plasma and liver lipids were compared in male Wistar rats. The plasma cholesterol level was significantly decreased in rats fed with a whey protein diet, compared with casein supplemented with or without cholesterol. These changes in plasma cholesterol were observed continuously for 70 days throughout the experiment. The concentrations of total lipids, cholesterol and phospholipid in liver were significantly decreased in rats fed with a whey protein diet compared to casein supplemented with cholesterol. There was a significantly higher influx of lipoprotein cholesterol into the plasma compartment after a casein diet than after a whey protein diet containing high cholesterol. These data suggest that dietary protein may induce different plasma lipids levels by modulating the rate of lipid influx into the plasma compartment in rats fed with a cholesterol-supplemented diet.