Vaccines are a very prominent example of this fear of chemicals (and just to get this out of the way, everything in the world is some chemical or combination of chemicals). Earlier this year, I wrote about one vaccine ingredient, formaldehyde, in an effort to clear up why and how it is used in vaccines, as well as showing that the amounts found in vaccines are safe. Just the Vax and Science-Based Medicine also have good write-ups on the preservative. Recently, someone asked me about another ingredient: monosodium glutamate (MSG).
What is Monosodium Glutamate?
Monosodium Glutamate (MSG), sometimes also called sodium glutamate, is the sodium salt of glutamic acid, a non-essential amino acid. It was first discovered in 1908 in Japan by Kikunae Ikeda. Ikeda isolated the specific compound responsible for the flavor found in dashi, a fish-based broth, that was uniquely different from other recognized flavors (salty, sweet, sour, bitter). As he experimented with the umami taste, Ikeda discovered that ionic glutamate was the substance responsible, and he tried various monovalent salts of glutamate to devise a way to use it as a seasoning in foods. These included barium, calcium, potassium, "ammonium, magnesium, zinc, cadmium, aluminum, copper, and iron" (Ikeda, 1909). However, these glutamate salts all had a metallic taste. The sodium salt of glutamate ended up being the most palatable and convenient to produce and use.
Concerns about MSG started to rise in the late 1960s and 1970s after a letter by Robert Ho Man Kwok published in the New England Journal of Medicine in 1968 described a symptoms he experienced after eating Chinese food. The publication of his letter was followed by letters from many other individuals, describing a wide range of non-specific symptoms. At the time, a number of culprits were suspected: cooking wine, salt and MSG. Only MSG was investigated. As the years passed, the range of symptoms expanded with more and more reports from people.
How Are We Exposed?
Glutamic acid is found in every food that contains protein and is responsible for the savory umami taste we associate with meats, fish, spinach, tomatoes, cheese, soy sauce and so forth. In its sodium form, glutamate is added to packaged foods, as well, to help enhance the flavor. It is also found in breast milk. Here's a brief list of some common foods and their glutamate content:
More information on the natural glutamate content of various foods can be found in the Food Standards Australia New Zealand 2003 Monosodium Glutamate Safety Assessment and on the Umami Information Center web site.
Another possible source of glutamate is in some influenza vaccines. More on this later.
Role in Metabolism
As mentioned above, glutamate is a nonessential amino acid, meaning that it is not something we need to get from our diet; our bodies can make it on its own, in addition to getting it from our diets. Our bodies use glutamate for cellular metabolism. It also serves as a neurotransmitter. In this regard, excess glutamate has been implicated in seizures, though more research is needed. Glutamate from the diet is largely oxidized into CO2 as a fuel for the gut, as well as metabolized into other nonessential amino acids. It is also believed to be very important for the function of the infant gut. Glutamate is a precursor of the α-amino acids proline and arginine, and the peptide glutathione, the latter of which is frequently cited by biomed advocates as beneficial for autism, however, much of the research in this area involves small sample sizes, increased risk of bias in the results, and has been conducted by dubious researchers, such as Mark and David Geier and Russell Blaylock.
How Much Is Too Much?
With the potential role glutamate plays in seizures and reports of Chinese Restaurant Syndrome, just how much glutamate intake is too much? Mouse studies have shown significant neuronal damage in infant mice at a blood levels of about 100-130 μmol/dl (~14.7mg glutamate for a 1-8g infant mouse, or 1.8g of glutamate per kilogram body weight). Mice, however, also happen to be a species that is highly sensitive to glutamate damage. In humans, blood levels of that amount have not been achieved, even at single doses of 150mg per kilogram body weight. Further, studies have shown that infants are just as good as adults at metabolizing glutamate. A daily intake of up to 6,000mg/kg is recognized as safe.
With regard to so-called Chinese Restaurant Syndrome (also referred to as MSG symptom complex), several large, double-blind, placebo-controlled trials failed to find a causal connection between MSG and the reported symptoms. There is some suggestion, though, that large doses of MSG taken without food cause more reactions than placebo, but the frequency of reports is low and of a transient nature, but these findings were inconsistent and unable to be reproduced.
What About Vaccines?
All of this has to do with food and dietary sources of glutamate, whether through the naturally occurring free ionized glutamate or through MSG. So what does this have to do with vaccines? Why would it be added to any vaccine?
In addition to its flavor-enhancing properties, MSG also happens to act as a stabilizer. They help to prevent chemicals from interacting or separating out, as well as preventing oxidation or damage from light. It is this ability to keep things from breaking down that MSG is added to vaccines, protecting them from being altered when "exposed to heat, light, acidity, or humidity".
Now that we know why it is added to vaccines, which ones actually contain MSG, and how much? Not many actually use it. Glutamate is added as a nutrient to the growth medium for MMR-II and is not in the final product in significant amounts; monosodium glutamate is added to FluMist (0.188 mg/0.2 mL dose); monosodium L-glutamate is added to ProQuad (.4mg), Zostavax (.62mg) and Varivax (.5mg); and potassium glutamate is added to RabAvert (1mg).
How do these discreet doses compare, then, to other sources and to what we know about safe daily intake and metabolism?
- 1/2 cup of peas contains 48 times the glutamate in Varivax and 127 times the amount in FluMist
- One cup of breast milk contains 352 times the amount found in Varivax and 936 times the amount in FluMist
- The safe, daily intake of glutamate is 12,000 times the MSG in Varivax and 32,000 times what is in FluMist
The flavor-enhancer monosodium glutamate has a long history of stories of bad reactions after eating it in foods, particularly from American-Chinese restaurants. However, the reports of adverse reactions are anecdotal and not supported by rigorous, scientific evidence. Indeed, when examined in placebo-controlled, blinded studies, MSG disappears as a causative agent for these symptoms.
In vaccines, MSG is used primarily as a stabilizer to prevent the vaccine from breaking down when exposed to light or to changes in temperature or acidity. In this role, each dose contains very little of the substance, being hundreds of times less than the exposure from a single serving of glutamate-containing foods and thousands of times less than the average, safe daily intake.
The bottom line is that there is little reason to fear dietary intake of MSG, and even less reason to be concerned about MSG in vaccines.
1kg = 1,000g = 1,000,000mg = 1,000,000,000μg
Here are some real-world examples of those weights (technically masses):
1kg = a 1L bottle of soda
1g = a paper clip
1mg = a very, very small snowflake
1μg = take your paper clip, cut it into a million pieces and take one of those
- Beyreuther K, Biesalski HK, Fernstrom JD, Grimm P, Hammes WP, Heinemann U, Kempski O, Stehle P, Steinhart H, & Walker R. (2007) Consensus meeting: monosodium glutamate - an update. European Journal of Clinical Nutrition, 61, 304-313. PubMed PMID: 16957679. Accessed online October 28, 2012 at http://www.ncbi.nlm.nih.gov/pubmed/16957679
- Burrin DG & Stoll B. (2009). Metabolic fate and function of dietary glutamate in the gut. The American Journal of Clinical Nutrition, 90, 850S-856S. PubMed PMID: 19587091. Accessed online October 28, 2012 at http://ajcn.nutrition.org/content/90/3/850S.full
- During MJ & Spencer DD. (1993). Extracellular hippocampal glutamate and spontaneous seizure in the conscious human brain. Lancet, 341, 1607-10. PubMed PMID: 8099987. Accessed online October 28, 2012 at http://www.ncbi.nlm.nih.gov/pubmed/8099987
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- Institute for Vaccine Safety. (2012) Excipients. Accessed online on October 28, 2012 at http://www.vaccinesafety.edu/components-Excipients.htm
- U.S. Centers for Disease Control and Prevention. (2011) Ingredients of Vaccines - Fact Sheet. Accessed online on October 28, 2012 at http://www.cdc.gov/vaccines/vac-gen/additives.htm#Facts
- U.S. Centers for Disease Control and Prevention. (2012) Vaccine Excipient & Media Summary. Accessed online on October 28, 2012 at http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/appendices/b/excipient-table-2.pdf
- Walker R. (1999) The significance of excursions above the ADI. Case study: monosodium glutamate. Regulatory Toxicology and Pharmacology, 30, S119-21. PubMed PMID: 10597625. Accessed online October 28, 2012 at http://www.ncbi.nlm.nih.gov/pubmed/10597625