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(Compiled by Adrienne Samuels, Ph.D., July, 2010)
Evidence of monosodium glutamate-induced adverse reactions comes from epidemiological studies that demonstrate that monosodium glutamate causes adverse reactions in humans(1-4); from studies and case reports published by concerned physicians(1, 5-41); and from reports of consumers who find their symptoms abate after discontinuing use of products that contain monosodium glutamate, but reoccur when monosodium glutamate is ingested.
The epidemiological studies done in the United States in the 1970s suggest that 25% to 30% of the population was intolerant of monosodium glutamate at levels then found in food. Considering the expanded use of monosodium glutamate and other MSG-containing food additives since that time, we conservatively estimate that approximately 40% of the U.S. population presently react adversely to MSG.
The Truth in Labeling Campaign (TLC)(44) receives letters daily from consumers who find that their adverse reactions abate when they eliminate monosodium glutamate from their food, drugs, and dietary supplements. A number of these letters have been reproduced on the TLC web page. See Consumers Tell Us That….
Ironically, industry-sponsored studies themselves provide examples of adverse reactions following ingestion of monosodium glutamate in monosodium glutamate test material(45-61). In discussing the flaws in industry-sponsored studies elsewhere, we have pointed to the fact that although each study is designed to minimize the number of reactions to monosodium glutamate test material, a number of reactions do occur; but if noted at all, any report of such reactions is most often tucked away in a table, while discussion in the body of the article and in the discussion section focuses on the fact that there were as many reactions to placebos as there were to monosodium glutamate test material. (See “Evidence of monosodium glutamate-induced adverse reactions_double-blind studies”.) Finally, it must be noted that one of the reasons that placebo responses roughly approximate the number of reactions to monosodium glutamate in industry-sponsored studies is the fact that in all of the double-blind studies referenced here, the placebos were laced with aspartame (which contains neurotoxic aspartic acid, a structural analog of the glutamic acid found in monosodium glutamate).
Although reports of adverse reactions are growing, there seems to be no incentive to publish case studies or case reports in the medical literature. No one compensates physicians for writing up case studies, and the FDA has collected, but never solicited, reports of adverse reactions to monosodium glutamate or other MSG-containing ingredients. There are studies that warn of hazards of MSG-ingestion, but they are studies of pathophysiology related to glutamate, not studies of adverse reactions per se. The one exception may be the work of He et al. who found that weight gain and obesity are related to ingestion of monosodium glutamate(62).
The adverse reactions noted (and summarily dismissed) in industry-sponsored studies of the safety of monosodium glutamate themselves present compelling evidence of the toxic potential of monosodium glutamate.
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