Umami taste of monosodium glutamate enhances the thermic effect of food and affects the respiratory quotient in the rat.
Having previously shown that orogastric stimulation with carbohydrates or sweeteners triggers an increase in metabolic rate and in respiratory quotient, we investigated the possibility that the umami taste of monosodium glutamate (MSG) could act similarly on metabolic responses to protein ingestion. Monosodium glutamate solutions (0.01 and 0.15 M) or vehicle were infused via an intraoral tube during a standardized meal of chow taken in a metabolic device linked to a computer capable of instantaneously measuring RQ and background (resting) metabolic rate in the freely behaving rat. Monosodium glutamate added to the food resulted in a rapid enhancement of metabolic rate that lasted about 30 min, i.e., the period of the anticipatory fraction of thermogenesis. The RQ also switched towards figures indicative of protein utilization. Monosodium glutamate is ineffective when administered independently of meal taking. Taken together these data indicate that the umami taste of MSG exerts an enhancing and specific action on metabolism that obeys the rules of anticipatory reflexes in the sense that both the metabolic rate and substrate utilization adapt from the very first announcement of ingestion of an extra load of protein.
Viarouge
C
C
Laboratoire de Neurobiologie des Régulations, CNRS URA 637, Collège de France, Paris.
Caulliez
R
R
Nicolaidis
S
S
D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D002151:Calorimetry; D004032:Diet; D005502:Food; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012119:Respiration / Q000187:drug effects*; D012970:Sodium Glutamate / Q000494:pharmacology*; D013649:Taste / Q000187:drug effects*
D012970:Sodium Glutamate