A new specific ageusia: some humans cannot taste L-glutamate.
A new specific ageusia was found in human subjects for monosodium L-glutamate (MSG). Four tests were successively applied to discriminate non-tasters and hypotasters from tasters. (i) NaCl and MSG thresholds, and (ii) suprathreshold sensitivity were evaluated using the up-and-down procedure. Only 73% of 109 subjects common to both tests demonstrated a sensitivity for MSG significantly higher than their sensitivity to NaCl, and hence a specific sensitivity to L-glutamate. The remaining 27% who showed no significant difference in sensitivity to MSG and NaCl solutions were considered as putative hypotasters. (iii) Perception profiles (time-intensity) for MSG and NaCl were tested in 58 subjects and appeared significantly different in 47 tasters (81%). This technique helped in identifying among putative hypotasters of tests 1 and 2 a few tasters who perceived equal intensity for isoconcentration of NaCl and MSG but who could discriminate isomolar solutions on other cues. Thus, 19% of subjects, for whom no significant differences were found between MSG and NaCl time-intensity profiles, remained in the hypotaster group. (iv) A discrimination task including 24 triangular presentations per subject of NaCl and MSG 29 mM applied to the eight most severe hypotasters showed that two subjects at least (two of 58; 3.5%) could not discriminate between both stimuli. Moreover, these subjects probably perceived identical sensations for MSG and NaCl solutions. The six other hypotasters (10.3%) could discriminate both stimuli at the limit of significance. None of these eight subjects were able to identify the typical umami taste in 29 mM MSG.
Lugaz
O
O
Laboratoire de Neurobiologie Sensorielle, 1 avenue des Olympiades, F-91744 Massy cedex, France.
Pillias
A-M
AM
Faurion
A
A
D000293:Adolescent; D000328:Adult; D004305:Dose-Response Relationship, Drug; D005260:Female; D018698:Glutamic Acid / Q000494:pharmacology*; D006801:Humans; D008297:Male; D012965:Sodium Chloride / Q000494:pharmacology; D012970:Sodium Glutamate / Q000494:pharmacology; D013649:Taste / Q000502:physiology*; D013650:Taste Buds / Q000502:physiology*; D013997:Time Factors
D018698:Glutamic Acid; D012965:Sodium Chloride; D012970:Sodium Glutamate