Effects of a high-protein diet with or without monosodium-glutamate in combination with inosine-monophosphate-5 on 24-h energy metabolism and appetite profile.

Abstract

Two amino acids that have received some attention as oral stimulators of appetite and metabolism are monosodium glutamate (MSG) and inosine-monophosphate-5 (IMP′5). The aim of the study was to determine if addition of MSG in combination with IMP′5 to a high protein diet has an effect on energy expenditure, substrate oxidation, satiety and relevant metabolites. Twelve subjects (6 male/6 female; age: 26±9 years, BMI: 22.6±2.2 kg/m2) were fed a high-protein diet during three 36-h respiration chamber experiments. In a randomized cross-over design they received a lunch without MSG+IMP′5, a lunch with MSG+IMP′5 added to the food, and a lunch with MSG+IMP′5 in capsules. The concentrations MSG and IMP′5 added were 0.6% [w/w] and 0.25% [w/w], respectively. Energy expenditure and its components and the appetite profile were measured. Desire to eat (24-h AUC) was significantly higher in the high-protein diet without MSG+IMP′5 compared to the high-protein diet with MSG+IMP′5 added to the food (1079±344 versus 833±372, p<0.05). No significant differences were seen in hunger, satiety, fullness or prospective consumption between the three conditions. With respect to energy expenditure and its components no significant differences were found between the three conditions. We conclude that addition of MSG+IMP′5 to a high-protein diet, either added to the food or in capsules, had a significant effect on desire to eat and no effect on energy metabolism.