Evidence suggests that dairy product consumption has beneficial long-term implications for the management of weight. Several mechanisms have been described that may explain the inverse relationship between dairy consumption and body weight, including the presence of both calcium and conjugated linoleic acid in milk. However, research has highlighted the role played by the protein content of milk is suppressing appetite and modulating blood glucose. Milk contains both casein and whey, but the effect of whey protein appears to be greater in causing satiety and reducing glycaemic response. Whey protein is able to stimulate the release of insulin, but when consumed with carbohydrates is also known to suppress glycaemic response. It may be then that whey protein reduces blood sugar levels when consumed with carbohydrates because of its insulinotropic effect from its high concentration of branched chain amino acids.
Research1 has investigated the effect of premeal whey protein on the subsequent energy intake and satiety levels of healthy individuals. In a randomised cross-over designed study, subjects were fed 10 to 40 grams of whey protein concentrate in 300 mL of water followed 30 min later by an ad libitum pizza meal. The results showed that >20 grams of whey protein suppressed food intake and >10 grams of whey protein reduced postmeal blood glucose levels and area under the curve (AUC). In a second experiment, subjects were fed 5 to 40 grams of whey protein concentrate and 10 grams of whey protein hydrolysate in 300 mL of water followed 30 min later by a preset pizza meal containing 12 kcal/kg body weight. In the subsequent preset pizza meal, whey protein reduced postmeal blood glucose and insulin AUC in a dose dependent manner, but the addition of the whey protein hydrolysate had no additional effect.
In this study, whey protein consumed before a meal reduced food intake, post meal blood glucose and postmeal insulin response. However, whey protein hydrolysate did not reduce postmeal blood glucose response suggesting that the effect may requite intact whey protein. Both whey proteins had an insulinotropic effect, but only the concentrate could reduce postmeal blood glucose levels. This suggests that insulin was not the main cause of the altered glycaemia. The decreased blood glucose levels may result from the delayed gastric emptying caused by the protein present in the whey protein concentrate. This would explain the lack of effect of the pre-digested hydrolysate despite the increase in insulin levels. Hydrolysate would not expect to decrease gastric emptying to the same degree as an intact whey protein concentrate because its protein structure is already pre-digested with ≈40 % as free amino acids and short peptides.
RdB
