味精安全问题

Umami/MSG:Safety Issues味精的安全问题味精的安全问题Outline 内容纲要内容纲要nBrief review of original issues leading to expression of concern in early 1970s 简要回顾上世纪70年代初引起关注的安全问题nBrief summary of safety views now 简单总结当前关于味精安全的观点Kwok RHMChinese-Restaurant Syndrome中国餐馆综合症中国餐馆综合症:796,1968 (letter)1968年年 新英格兰医学杂志新英格兰医学杂志（通讯）（通讯）nFirst report of adverse symptoms in humans associated with the ingestion of Chinese food that suggested a possible link to MSG().首例报道人体摄入中国食品后出现不适症状可能与所添加的味精有关（也可能是其他添加成分）nAn anecdotal case-report.n单例报告（缺乏足够科学依据）Schaumberg HH et al.Monosodium L-Glutamate:Its Pharmacology&Role in the Chinese Restaurant SyndromeScience 163:826-828,1969谷氨酸单钠的药理学及其在中国餐馆并发症中的角色谷氨酸单钠的药理学及其在中国餐馆并发症中的角色科学科学163期，期，826-828页，页，1969Skeletal stunting骨萎缩骨萎缩Marked obesity明显肥胖明显肥胖Sterility 不育不育Hypothalamic lesions下丘脑损伤下丘脑损伤MSG INJECTED注射味精后注射味精后Olney JW.Brain Lesions,Obesity and Other Disturbances in Mice Treated with Monosodium Glutamate.SCIENCE 164:719-721,1969.小白鼠注射味精后出现大脑损小白鼠注射味精后出现大脑损伤，肥胖以及其他系统紊乱伤，肥胖以及其他系统紊乱1969年科学杂志年科学杂志nConventional Toxicologic database for review by JECFA was very extensive,including acute,subchronic&chronic toxicity studies in rats,mice&dogs,together with studies on reproductive toxicity and teratologyn供食品添加剂联合专家委员会审查的常规毒性数据资料非常完整，包括大白鼠、小白鼠和狗的急性，亚慢性，慢性毒性研究以及遗传性毒性和畸形学研究。nGLU has very low acute toxicity(15,000+mg/kg po)in rats and micen谷氨酸对大、小白鼠具有极低的剧毒性（15000+mg/kg po）nNo specific adverse effects in chronic and sub-chronic studies up to 2 yr()n两年内，在慢性、亚慢性研究试验中未有明显副作用（大、小白鼠食物中味精占4%，小狗食物中添加10%）nReproductive and teratology studies negativen生殖和畸形研究无异常The Issues 问题问题Neurotoxicity神经毒性研究神经毒性研究Barriers to Neurotoxicity efficiently uses ingested GLU(MSG)as E-source(95+%).n胃肠道能有效地吸收95%以上的谷氨酸钠作为能源nGut is thus a barrier to GLU entry into blood.n肠道因此能阻止谷氨酸进入血液中 prevents GLU penetration into brain.n血脑屏障阻止谷氨酸渗透到大脑nOnly oral doses of MSG by gavage can raise plasma GLU enough to get GLU into brainn只有灌喂大剂量的味精，才会致血浆中的谷氨酸含量升高，而进入到大脑 n食物中添加的味精不会有这种效果Adult males(80 kg)quickly ingested MSG,12.7 g(150 mg/kg)in solution.成年男子（体重约80公斤）能很快吸收溶液中12.7g（约150毫克每公斤）的味精Time(minutes)060120180240Plasma GLU(nmol/ml)100200300400500Arrows=meal or snack 箭头代表摄取的食物或点心Meals:0745,1215,1800 h 饮食时间：0745，1215，1800Data are means sem(n=10)数据：均值标准差Black circle:no MSG黑圈表示不含味精White circle:MSG.白圈表示含有味精Time(minutes)060120180240Plasma PROLACTIN(ng/ml)510152025TRH PLACEBOMSGPROTEIN MEALStegink LD et al Am J Obstet Gynecol 122:70-78(1975)Monkey study.猴子实验猴子实验Highest dose(400 mg/kg iv,open circles)produced plasma GLU 70-times normal.Battaglia FC.J Nutrition 130:974S-977S(2000)Lactating women ingested 100 mg/kg MSG in capsules with water,and milk samples were taken at the indicated times thereafter.From:Baker GL et al.,Factors influencing dicarboxylic amino acid content of human milk.In:,Filer LJ et al.,ed.New York,Raven Press,1979,pp.111-123.哺乳期女性加水摄入 100 mg/kg 的胶囊，对其后特定时间的母乳样品进行检验表明：这一剂量使得血液谷氨酸浓度在这一剂量使得血液谷氨酸浓度在30-45分钟内从分钟内从 From:Baker GL et al.,Factors influencing dicarboxylic amino acid content of human milk.In:,Filer LJ et al.,ed.New York,Raven Press,1979,pp.111-123.影响人体母乳二氨基酸浓度的因素谷氨酸：生物化学和生理学进展Brain Issues 大脑问题大脑问题 Brain Issues大脑问题大脑问题 nThe human brain is unaffected by the very high plasma(GLU)following high dose MSG intaken摄入大量的味精导致的血浆中高谷氨酸含量不会对人体大脑产生影响nNo dose of MSG has yet been given to humans high enough to induce CNS effects.n至今亦未发现食用味精会影响人体中枢神经系统CRS/AllergyStudying MSG Symptom Complex味精综合症研究味精综合症研究SYMPTOMS ATTRIBUTED TO MSG:味精所致症状味精所致症状nBurning,tightness,numbness in upper chest,neck and face.发烧，身体发紧，胸腔上部发闷，脖子、面部发麻nDizziness,headache 眩晕，头疼nChest pain,palpitation 胸口痛，心悸nWeakness 乏力nNausea,vomiting 反胃呕吐nBronchospasm(asthmatics)哮喘nHives(urticaria)麻疹nProtocol A:self-styled MSG-sensitive individuals.Fasted,challenge with placebo or MSG(5 g in liquid).n实验A：130例自认为MSG过敏者，禁食，以安慰剂或MSG(5克液体)进行盲试。nProtocol B:Subjects had positive response of 2 symptoms toeither or both treatments in A(i.e.,placebo responderstoo).Fast,challenge with 0,1.25,2.5 or 5 gMSG(in liquid).n实验B:对A中，出现阳性反应的实验对象，超过2种症状（例如：对安慰剂反应也一样）。禁食，以0，1.25，2.5或5克MSG(液体)进行盲试。Geha RS et al.,J Allergy Clin Immunol 106:973-80,2000nProtocol C:Subjects had positive response of 2 symptoms to 5g MSG but not placebo in A or B.Fast,placebo(suc-rose)or MSG(5 g),in capsules().Do twice.n实验实验C:对A和B中阳性反应的实验对象-对5克MSG出现超过2种症状（对安慰剂没有），禁食，以胶囊性的安慰剂（蔗糖）或MSG(5克)，进行盲试。重复实验。nProtocol D:Subjects had positive response to both MSG chal-lenges in C.Fast,breakfast&placebo(sucrose)or MSG(5 g),in capsules().Do three times.n实验实验D:对C中MSG治疗出现阳性反应的实验对象，禁食，早餐加胶囊性安慰剂（蔗糖）或MSG(5克)，进行盲试。重复3次实验Geha RS et al.,J Allergy Clin Immunol 106:973-80,2000Geha RS et al.,J Allergy Clin Immunol 106:973-80,2000Protocol A Results:实验实验A结果结果 2 symptoms with MSG&0/1 with placebo.n MSG组超过2种症状出现+安慰剂组1个:2 symptoms with MSG&placebo.n 超过2种症状出现，味精和安慰剂:2 symptoms with placebo&0/1 with MSG.n 安慰剂组超过2种症状出现+MSG组1个 0 or 1 symptoms with MSG&placebo.n 没有或1种症状出现：MSG+安慰剂Geha RS et al.,J Allergy Clin Immunol 106:973-80,2000Protocol B Results:实验实验B结果结果nn=86 from had 2 symptoms with a treatment(blinded:placebo MSG),and included in.69 completed.n对2种症状进行治疗（双盲：安慰剂或MSG）nOvernight fast,challenge with 0,1.25,2.5 or 5 g MSG.n禁食过夜，按0，1.25，2.5或5克MSG看结果Geha RS et al.,J Allergy Clin Immunol 106:973-80,2000nn=19/69 reported 2 symptoms to 5 g MSG but placebo.n19/69例报道，5克MSG下有超过2种症状出现，没有安慰剂 the symptoms occurred in as in.n14/19例中同样症状出现，类似于A实验n因此，14/130表现出对5克MSG的可重复性反应Protocol C Results:实验实验C结果结果Geha RS et al.,J Allergy Clin Immunol 106:973-80,2000 3 placebo-MSG challenges must give positive response to MSG,no response to placebo.Give MSG.n1995年美国实验生物学联合会味精组：3种安慰剂-味精治疗必须引起同样的对味精的阳性反应，对安慰剂没有反应，味精应该以胶囊的形式给予。nn=19 had 2 symptoms in&with MSG&no symptoms with placebo.agreed to be studied.nN=19时，实验A和B的味精组都有超过2种症状出现，安慰剂组没有症状出现，n=12时，实验一致。Protocol C Results:实验实验C结果结果Geha RS et al.,J Allergy Clin Immunol 106:973-80,2000nTwo separate tests of MSG(5 g)vs placebo.n分开测试味精（5克）和安慰剂味精组超过2种症状出现，安慰剂组没有症状出现，但症状不同。Geha RS et al.,J Allergy Clin Immunol 106:973-80,2000CONCLUSION:Using criteria established by the 1995 FASEB panel,none of the individuals who claimed a sensitivity to MSG actually showed this sensitivity when tested under blinded conditions.结论：根据1995年美国实验生物学联合会（FASEB）制定的标准，对那些声称味精过敏的个体进行双盲试验表明他们未表现出敏感性。CRS Symptoms in Humans人体的人体的MSG症状症状:Early studies claiming that MSG induces asthma in asthma patients have been confirmed in recent studies involving greater numbers of patients.n哮喘：早期研究声称味精会导致哮喘病人病情发作，但近期众多数量病人的研究中未得到证实Stevenson DD.Monosodium glutamate and asthma.J Nutr 130:1067S-1073S,2000味精和哮喘 2000年 营养学杂志.MSG Symptoms in Humans人体的人体的MSG症状症状:65 subjects with idiopathic urticaria;single-and double-blind studies using 2.5 g MSG challenges vs placebo(capsules).n荨麻疹：使用2.5g味精和安慰剂（胶囊）治疗65例特发性荨麻疹，单盲和双盲研究n“.MSG is a distinctly uncommon cause or exacerbant of chronic urticaria,if it induces urticaria at all.We were certainly unable to demonstrate MSG-induced urticaria in any of our chronic urticaria patients,even those who believed MSG provoked their urticaria in the past.”n即使味精会引发荨麻疹，那也很少会引起或加剧慢性荨麻疹。我们无法确证慢性麻疹病人中多少是由味精所致的，尽管有些人认为是因为过去食用味精所致病。Simon RA.Additive-induced urticaria:Experience with monosodium glutamate(MSG).J Nutr 130:1063S-1066S,2000.Bazzano G,DElia JA,Olson RE Science 169:1208-1209,1970.Adult human subjects ingested a chemically-de-fined diet supplying all of the essential amino acids in optimum amounts,plus glutamic acid as the sole source of non-essential nitrogen,for 14-42 days.No subjects developed the Chinese restaurant syndrome.No changes in weight,irrita-bility,appetite or mentation were noted.给予成人研究对象适量的化学性饮食包含所有必须氨基酸，并以谷氨酸作为非必须氮源，14-42天后，没有发现中国餐馆综合症，体重、情绪、胃口以及智力都没有变化。