Does monosodium glutamate interact with macronutrient composition to influence subsequent appetite?

The influence of flavour enhancers such as monosodium glutamate (MSG) on satiation and satiety is unclear, and the present study aimed to explore this by examining the effects consumption of soups varying in MSG (1% MSG added or no MSG) and macronutrient content (added carbohydrate, protein or control) had on appetite. 24 non-obese, low-restraint male participants consumed a fixed portion of soup and rated their appetite before, immediately after intake and at 15 minute intervals for 120 min post-ingestion across six sessions. Added MSG significantly increased flavour pleasantness and tended to result in a smaller decrease in hunger immediately after soup ingestion. MSG also reduced rather than enhanced feelings of fullness immediately after ingestion of the high protein soup. As expected, hunger increased, and fullness decreased, over the subsequent 120 min, but the increase in hunger was significantly lower in the MSG than no-MSG conditions with the protein soup between 30 and 60 min post-ingestion. Overall these data suggest that MSG may have a bi-phasic effect on appetite, with reduced satiation mediated by effects on palatability, but potential for enhanced post-ingestive satiety particularly in the context of protein ingestion.