Whey and casein are two proteins that are isolated from milk. They are available freeze dried as powders. Whey protein is popular amongst athletes for its skeletal muscle building effects. This relates to the high concentration of branched chain amino acids that are present in the protein. Whey is more rapidly absorbed that casein protein when taken in isolation, causing a rapid rise in blood levels of amino acid, and this may produce a significant anabolic effect when compared to casein. Whey protein also produces significant immune stimulatory response compared to casein, and this relates to the presence of a number of proteins contained within the whey fraction that may stimulate the immune function of mammals. However, casein protein also has certain advantages, one being that because of its slower absorption, it may provide better appetite regulatory properties that whey. Both proteins therefore have interesting physiological effects that make them of interest to nutritionists.
Comparisons of whey and casein protein have therefore been made in humans. Recently, researchers assessed the ability of whey and casein protein to reduce the postprandial lipaemia in healthy human subjects1. Over the course of 12 weeks, subjects consumed either 60 grams of whey protein or 60 grams of casein, along with 63 grams of milk fat. Consumption of the whey protein significantly reduced the plasma concentrations of the apoB48 lipoprotein component (present in chylomicrons), indicating that postprandial lipid absorption had been reduced or that lipids were rapidly cleared from circulation. However, the casein protein significantly increase glucagon-like peptide 1 in comparison to whey, supporting an appetite regulatory role for casein. The authors claimed that this suggests that whey would have protective effects against cardiovascular disease, but chylomicrons are formed in the small intestine, and associate with dietary lipid absorption, and are not likely associated with cardiovascular disease.
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