Yummy Umami: No, You Won't Die!
How will slurping up that steaming bowl of ramen influence your health? Listen to those advertisements, and you, like I, learn that cow's milk causes cancer, apples are full of cyanide, and ramen induces vomiting. Please! When are we going to separate fact from fiction? It's time to question the validity all those "truths" surrounding various foods. Monosodium glutamate (MSG) is a controversial chemical, rumored to cause obesity and nausea, although scientific evidence has been shaky. The blame initiated with propaganda touting all things "natural" as "healthy", and labeling MSG as "unnatural". True, MSG is extracted using fermentation and microorganisms, but it originally comes from animal or plant protein [Kusumoto]. Does this mean that it's dangerous, or even that artificial? Other foods widely perceived as "natural" are actually just as synthetic as MSG: genetically-modified seedless grapes, rennet-processed cheese, and fermented potato vodka. These are just as man-made as MSG, while MSG is just as natural as these. Why, then, does MSG get such a bad rap? It is mentally and physically gratifying; it stimulates the digestive tract, makes the digestion of food efficient, and simply tastes delightful. MSG, which may actually be beneficial, should not be vilified since it is just as "natural" as myriad other foods.
What are the hard facts about MSG? MSG is just like any other isolated food chemical. Sucrose crystals taste sweet, table salt crystals taste salty, and MSG crystals taste umami. Although just an emerging term, umami describes a "savory" flavor. It has joined the four other main flavors in food science, which include sweet, salty, sour, and bitter [Renton]. The delicious umami taste obtained from MSG foods is caused by L-glutamate, an amino acid [Lehrer 57]. L-glutamate is naturally present in animal flesh, parmesan cheese, and anything that evokes that tasty savory flavor [Lehrer 60]. To parallel this concept, sucrose is naturally found in sugarcanes and sugar beets. These plants are chemically processed to synthesize the crystals that we spoon into our coffee, among other foods, and we think that this is completely safe! Likewise, L-glutamate, traditionally extracted from plant or animal protein, is now mostly made using enzymes and fermentation and attached to a sodium molecule to create stable MSG crystals [Kusumoto]. Companies, restaurants and families sprinkle this into soups, sauces, etc. What makes the industrial refinement processes of sugar different from that of MSG? Is MSG alone in causing health problems such as obesity?
Those who avoid MSG claim that it makes us overweight and obese. In an INTERMAP study in 2008, the food intakes of 752 Chinese adults were analyzed. The amount of MSG consumed was calculated based through observing how frequently people cooked with MSG or soy sauce. If participants had consumed food from restaurants or grocery stores, those places were contacted for nutritional information. A body mass index (BMI) is a formula used to measure body fat. According to the World Health Organization, a BMI equal to or higher than 23.0 kg/m2 is defined as "overweight" for Asian populations [He]. The average intake of MSG was 0.33 g per day per participant, although some people were "nonusers of MSG" [He Table 1]. For nonusers, the average BMI was 22.3 kg/m2. Conversely, the top users of MSG (sectioned off to 27% of the study population), had an average BMI of 23.5 kg/m2. Dietary analysis showed that the people who had a higher intake of MSG also had a higher intake of fat, cholesterol and animal protein, and a lower intake of vegetable protein and carbohydrates, compared to those who were nonusers [He Table 1]. He postulated that MSG increased the participants' appetites, so they ate more food than they needed and therefore became fatter.
Further analysis, in contrast, shows that MSG does not cause weight gain. Correlation does not mean causation, and MSG may not be completely responsible for the higher average BMI. Instead of MSG causing the high intake of protein, what if the converse is true? L-glutamate is widely present in animal protein [Lehrer 60]. Also, perhaps the lifestyles of the rural participants mean that they aren't educated about the effects of eating too much fat, or rely solely on seasonal foods. Another drawback of He's study is that eating 0.33 g of MSG per day is not extremely significant. Just 10 g of the much-used soy sauce in Chinese cuisine contains 0.11 g of L-glutamate [Renton]! Our bodies even produce 40 g of glutamate, daily, making that extra 0.33 g of dietary L-glutamate trivial [Renton]. In a similar study in 2010, 1282 Chinese adults were enrolled, which is nearly double that in He's study [Shi 457]. The only significant changes were that participants chose fewer protein-rich foods (which are composed of more glutamate) and more complex carbohydrates [Shi 459]. This is understandable; the higher amount of L-glutamate probably caused the brain to adapt to a lower protein diet [Shi 457]. The intake of fruits and vegetables remained the same, as did the total number of calories consumed [Shi 459]. Shi showed no correlation between an intake of MSG and weight gain [Shi 457]. So, does MSG actually have an impact on our bodies?
If used the correct way, MSG's influence on flavor allows us choose more nutrient-dense foods! Generally, fat-free and salt-free foods taste bland, which is why people choose greasy or salty foods [Jinap]. Who would choose a dry, bland wedge of pita bread (fat free, made solely out of flour and leavening agents)or a raw broccoli floret when salty nachos smothered in cheese and sour cream beckon? However, an overconsumption of fat or sodium promotes weight gain. MSG itself is tasteless, but once introduced into fat-free foods, it enhances the flavors of the food. Eggs taste more "eggy", and tomatoes taste "better" [Renton]. Now, pita bread coated in barbeque, herb, garlic, or any other MSG seasoning is much more receptive and tasty. Broccoli with a sprinkling of parmesan cheese is much more palatable. For the same weight, MSG has less sodium than plain table salt (they both have ones sodium molecule attached, but the chloride is much lighter than the glutamate, C5H9NO4) [Lehrer 57]. We'd feel just as satisfied, and won't consume as much fat or sodium [Jinap]. In theory, if we add MSG to a varied diet, we can not only eat fewer empty calories and sodium, but also satisfy our taste buds! Opponents may argue that this liberal sprinkling of MSG will ultimately be detrimental, but that can be said of any nutrient. For example, those multivitamins may give you a boost, but chugging a whole canister of them will leave you poisoned. Any food that is over-consumed will kill – even broccoli!
MSG also contributes to digestive health. Food digestion starts in the mouth, and the wonderful taste of umami, from MSG or other sources, stimulates the salivary glands to release saliva. The saliva wets and prepares the food for chewing [Jinap]. This is important for the elderly, or those who have weak teeth or jaws, especially in eating tough protein items such as fibrous animal flesh. In addition, the saliva present after swallowing the food allows for better oral hygiene, since the proteins in saliva improve immunity and reduce the bacteria in the mouth [qtd in Yamamoto 845S]. Our stomach and intestinal linings use L-glutamate as a source of energy to digest food more easily, and it also induces the pancreas to release more digestion enzymes [Yamamoto 844S, Jinap]. This means that in a dish of stir-fried vegetables with MSG, minerals are more easily absorbed into the intestinal lining and bloodstream [Jinap]. Mucus is a secretion from the tissue linings and it prevents stomach acid and salts in the partially-digested food from reacting with the cell lining and forming painful ulcers [Jinap]. The addition of MSG to foods is especially helpful to the elderly, especially when they eat very little or are insensitive to delicate smells and tastes [Yamamoto 846S]. In addition, this is a cost-efficient way of persuading hospitalized or depressed people who have no appetite to eat more food [Yamamoto 846S].
Aside from research studies, why not look at our basic physiology? L-glutamate, a component of MSG, is evolutionarily desired by the body. Umami is traditionally encountered in high-protein foods that the body needs in order to carry out daily functions. We metabolize these foods for energy and the synthesis of protein molecules such as enzymes, transport proteins, muscle fibers, hair etc. [Chaudhari 199, Yamamoto 846S]. Umami has various sources; parmesan cheese (free L-glutamate) is one, as is MSG powder (L-glutamate bound to sodium) [Renton]. There are a variety of taste receptors that elicit the umami sensation, which demonstrates that the body has evolved to want L-glutamate. One of these receptors is the receptor combination of T1R1 and T1R3 in humans [Nelson 201]. Other combinations elicit other tastes; a suitable analogy is based on the activation of T1R1 and T1R2, which is interpreted as sweetness [Nelson 201]. Sweetness, the universal signal of carbohydrates and energy, also comes in many forms, such as the "natural" fructose in cherries and the processed sucrose (glucose + fructose) in toffee. Both are universally regarded as safe. Free L-glutamate amino acids in parmesan cheese do not negatively affect our bodies, so MSG, which is digested by the body into sodium ions and free L-glutamate, should not induce illness.
Is it justified to victimize MSG because it is processed? Many foods that we eat are equally "artificial", from simple sugar crystals to the vitamin-enriched bleached flour used to make perfectly square slices of bread. The manipulation of "nature" is not necessarily unhealthy; cheeses made with chemicals are safe! In fact, is the milk used even "natural", when we consider the hormone injections and antibiotics used for continuous, uniform lactation? If not, we already consume "unnatural" food with zeal and confidence. Why, then, are we singling out MSG? From targeting MSG's synthesis to hatching up "controversies" concerning other "artificial" foods, propaganda can blatantly skew scientific fact. This not only extrapolates to widely favored genetically modified foods such as corn, but also to the modification of nature in the first place. Why do we prize pig gene manipulation, but react to any stem cell DNA investigation with chagrin? Lobbyists or unsatisfied customers with monetary goals in mind can use emotional appeal and the media to sway a public crusade against almost anything, even if it's advantageous! Perhaps we should stop repeating the myths that are constantly drilled into our brains, and actually visit the science standing forlornly behind all the hype.
Works Cited
G. Nelson et al., "An Amino-Acid Taste Receptor," Nature 416 (2002): 199-202. Nature Publishing Group. Macmillan Publishers Limited. Web. 4 Nov. 2010.
He, Ka, and Liancheng Zhao. "Association of Monosodium Glutamate Intake With Overweight in Chinese Adults: The INTERMAP Study." Obesity 16.8 (2008): 1875-880. Obesity, A Research Journal. Nature Publishing Group, 22 May 2008. Web. 13 Nov. 2010.
Lehrer, Jonah. Proust Was a Neuroscientist. Boston: Houghton Mifflin, 2008. Print.
Yamamoto, Shigeru et al., "Can Dietary Supplementation of Monosodium Glutamate Improve the Health of the Elderly?" The American Journal of Clinical Nutrition 844S-849S 90.3 (2009): 844-49. The American Journal of Clinical Nutrition. American Society for Clinical Nutrition, 2009. Web. 7 Nov. 2010.
Renton, Alex. "If MSG Is so Bad for You, Why Doesn't Everyone in Asia Have a Headache?"The Observer. The Guardian, 10 July 2005. Web. 8 Dec. 2010.
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Awesome science review. Well written and informative. Thanks!
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