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“Discovery” of MSG …

“Discovery” of MSG …. An attentive taster will find out something common in the complicated taste of asparagus, tomatoes, cheese and meat, which is quite peculiar and cannot be classed under any of the well defined four taste qualities, sweet, sour, salty and bitter.

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“Discovery” of MSG …

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  1. “Discovery” of MSG … An attentive taster will find out something common in the complicated taste of asparagus, tomatoes, cheese and meat, which is quite peculiar and cannot be classed under any of the well defined four taste qualities, sweet, sour, salty and bitter. (Prof. K. Ikeda’s presentation at the 8th Int’l Congress Appl. Chem., Chicago, 1912) Dr. Kikunae Ikeda (1908)

  2. Basic taste categories Z Chicken Umami Sour Beef Salty Y Bitter Sweet X Yamaguchi, S. (1987)

  3. Preference for umami is related to levels of dietary proteins NaCl NaCl Umami (MSG) Umami (MSG) Umami (MSG) Umami (MSG) Umami preference is a marker of protein nutrition! NaCl NaCl Torii et al., In Umami: a basic taste, pp513-563 (1987)

  4. Tomato’s full, rounded 'meaty' flavor comes from its heavy load of glutamates, and this flavor is reinforced by its unique crimson color. Green (mg/100g) Pink Red 180 Full ripe 160 140 120 100 80 60 40 20 0 Asp Ser Glu Gly Ala Val Met Ile Leu Tyr Phe Lys His Arg

  5. Free glutamate in breast milk (mg/100g) Total Glu intake = 0.393 g/kg/day! 20 18 16 14 12 10 8 6 4 2 0 Tau Asp Thr Ser Gln Glu Gly Ala Val Cys Met Ile Leu Tyr Phe Orn Lys His Arg

  6. “No MSG” labels … • “While technically MSG is only one of several forms of free glutamate used in foods, consumers frequently perceive the term MSG to mean all free glutamate. • For this reason, FDA considers foods whose labels say "No MSG" or "No Added MSG" to be misleading if the food contains ingredients that are sources of free glutamates, such as hydrolyzed protein.” http://vm.cfsan.fda.gov/~lrd/msg.html

  7. Glutamic acid metabolized during digestive absorption Mouth Glutamic acid from Food Small intestines mucous membrane epithelial cell Hepatic portal vein Liver Glutamic acid Glutamic acid Blood 100% > 90% Alanine, Glutamine Thermogenesis Energy Protein biosyntheses

  8. Gastric Afferents of Vagus 45 45 Liquid diet 35 35 MSG (+) Afferent Nerve Response (spikes/sec) 25 25 MSG (-) 15 15 5 5 5 10 17 0 Time (min) An liquid diet without Glu, does not elicit chemoreception

  9. mGluR1 Sensors for Glutamate exist on Tongue & Alimentary tract Tongue (Taste buds) Stomach mGluR1 & T1R1 mGluR1 mGluR1 T1R1 Small Intestine mGluR4 & T1R1 mGluR4 mGluR4 T1R1 Intake of protein is recognized by umami receptors in the tongue and visceral receptors in the GI tract. Large Intestine mGluR4 mGluR4 & mGluR4 & T1R1 T1R1

  10. Saline Val Leu Ile Lys Trp Thr Phe Met Glu Gly Arg Ala Pro Cys Asp His Gln Asn Ser Tyr 0 10 20 30 (D, Spikes/sec) Increase of Gastric Afferent Activity Glutamate-Sensing by the Gastric Vagus Amino Acid solution (150mmol/L, 2mL) ** AAs

  11. Clinical Trial: Implications Glutamate facilitated the gastric emptying of a protein-rich meal without influence on that of water or carbohydrate meal. Free glutamate is an important substance for efficient protein digestion and absorption. Gastroenterology (2006) 130(4), S2, A246,

  12. Summary Activated forebrain regions and signaling pathways After infusion of taste substances in the stomach, several forebrain regions (cortex, basal ganglia, limbic system, and hypothalamus) were activated. MSG-induced brain activation, but not glucose-induced one, was substantially reduced after vagotomy. The results clearly provide direct evidences of brain activation by post-oral stimuli with taste substances via either neural (vagal) or humoral signaling pathway.

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