MONOSODIUM GLUTAMATE INTOLERANCE
Monosodium glutamate, a flavor enhancer common in Chinese cooking, is used increasingly to flavor Western foods. In addition, some foods, such as tomato, mushrooms, and cheese, contain natural glutamates that resemble Monosodium glutamate. A glutamate is a derivative of the amino acid called glutamic acid that is an essential part of proteins.
Persons sensitive to Monosodium glutamate report a variety of symptoms known as the “Chinese Restaurant Syndrome” or “Kwok’s Syndrome.” Symptoms may include facial flushing, pain in the face and the back of the neck, headache, tingling and burning sensations, blurred vision, nausea and vomiting, increased heartbeat, chills, and shaking. Several incidents of severe asthma have been attributed to the ingestion of Monosodium glutamate; depression, irritability, and other mood changes have also been reported.
Experts are widely divided on the subject of Monosodium glutamate sensitivity. A recent review stated that results of a number of research studies “led to the conclusion that ‘Chinese Restaurant Syndrome’ is an anecdote applied to a variety of postprandial [occurring after a meal] illnesses: rigorous and realistic scientific evidence linking the syndrome to Monosodium glutamate could not be found.” On the other hand, some clinicians have estimated that the prevalence of Chinese Restaurant Syndrome may be as high as 1.8% of the adult population.
This chapter will provide you with information on what you may experience if you are sensitive to glutamates. It discusses how glutamates may cause your symptoms, and how to reduce your intake of glutamates without causing any nutritional deficiencies in your diet.
How Monosodium glutamate
Causes Symptoms
Monosodium glutamate is the sodium salt of glutamic acid, an amino acid. Glutamate is the active ingredient in the compound.
One theory to explain sensitivity to Monosodium glutamate links its action to abnormally high levels of acetylcholine, a neurotransmitter that acts on the brain and central nervous system. Because glutamate acts as a building block in the synthesis of acetylcholine, as well as other physiological chemicals, the symptoms of Monosodium glutamate sensitivity may be caused by excessive levels of neurotransmitters that develop in a short period of time. Toxic levels of acetylcholine may explain the symptoms of the Chinese Restaurant Syndrome.
The usual source of glutamate is food proteins, where it is combined with other amino acids. Before glutamate is free to be absorbed by the body, the pep-tide bonds in these proteins must be broken by enzymes in the process of digestion. Because this process is gradual, it controls the level of free glutamate in the body. According to the theory of “neurotransmitter toxicity” when Monosodium glutamate is eaten, glutamate enters the bloodstream rapidly because no peptide linkages need to be broken. Clinical studies have shown that an Monosodium glutamate dose of 0.1 gram per kilogram of body weight can induce plasma glutamate levels to rise to 15 times the normal concentration in about one hour. However, a relationship between plasma glutamate levels and symptoms has not been demonstrated in well-conducted research trials.
Some practitioners have noticed a deficiency of vitamin B6 (pyridoxine) in a number of Monosodium glutamate-sensitive persons. This deficiency could reduce the breakdown of glutamate in the liver, thus prolonging high plasma glutamate levels and causing symptoms to worsen.
Symptoms Possibly Caused by Monosodium glutamate
The following symptoms are reported to be caused by Monosodium glutamate:
| Flushing |
| Tightness around face, jaw, and chest; numbness of face |
| Tingling, burning of face and chest |
| Rapid heartbeat |
| Nausea, diarrhea, stomach cramps |
| Headache, especially at back of head and neck |
| Weakness, dizziness, balance problems, staggering |
| Confusion, slurred speech |
| Blurring of vision, difficulty focusing, seeing shining lights |
| Chills and shaking, excessive perspiration |
| Difficulty in breathing |
| Symptoms of asthma (in persons with asthma) |
| Water retention, thirst |
| Insomnia, sleepiness |
| Stiffness, heaviness of arms and legs |
| Mood changes, such as irritability |
| Depression, paranoia |
Symptoms of Chinese Restaurant Syndrome are reported to usually occur within 30 minutes of eating a meal high in Monosodium glutamate. Symptoms of asthma, however, have been reported to occur 1 to 2 hours after Monosodium glutamate ingestion and even as long as 12 hours later.
Management of Monosodium Glutamate Sensitivity
A “safe level” of Monosodium glutamate in foods cannot be set because a number of different factors contribute to plasma levels of glutamate, only one of which is the Monosodium glutamate added to food. Glutamate is a natural component of the body, where it plays an essential role in metabolism. Enzymes called transaminases in the liver allow glutamate to interact in a variety of reactions, and free glutamate is also found in muscle, brain, kidneys, and other organs. A person who weighs 70 kilograms has the equivalent of about 12 grams of Monosodium glutamate in his or her body. Whether or not any particular plasma level can be considered “safe” is not known.
Milk contains natural free glutamate. The daily intake of a 3 kilogram infant obtained from 480 grams of mother’s milk is 3.75 grams (1.25 g/kg body weight).
The Joint FAO/WHO Expert Committee on Food Additives has evaluated Monosodium glutamate and has judged that no restriction is necessary for the use of Monosodium glutamate in food. This means that Monosodium glutamate can be added to any prepared food to the level that the manufacturer considers optimum for enhancing the flavor of its product.
Because Monosodium glutamate is a food additive that appears on the Generally Recognized as Safe (GRAS) list, a food manufacturer is not required by law to include Monosodium glutamate in a list of ingredients on product labels. Listing Monosodium glutamate as an ingredient is voluntary on the part of the manufacturer.
Monosodium glutamate-sensitive persons should restrict their intake of Monosodium glutamate as much as possible. Because alcohol seems to increase the rate of absorption of many foods as well as Monosodium glutamate, drinking alcoholic beverages while eating Monosodium glutamate-containing foods probably increases both the severity and rate of onset of symptoms. In addition, eating foods containing Monosodium glutamate on an empty stomach seems to increase the adverse effects of Monosodium glutamate.
Sources of Monosodium glutamate
The following flavorings contain Monosodium glutamate and may appear on food labels:
| ♦ Accent | ♦ Hydrolyzed vegetable protein (HVP) |
| ♦ Ajinomoto | ♦ Hydrolyzed plant protein (HPP) |
| ♦ Zest | ♦ Natural flavoring (may be HVP) |
| ♦ Vetsin | ♦ Flavoring |
| ♦ Gourmet powder | ♦ Kombu extract |
| ♦ Subu | ♦ Mei-jing |
| ♦ Chinese seasoning | ♦ Wei-jing |
| ♦ Glutavene | ♦ RL-50 |
| ♦ Glutacyl |
Many prepared foods contain Monosodium glutamate or one of the above flavorings. Foods containing these additives include
Canned meats
Prepared dinners and side dishes
Canned soups
Dry soup mixes
Gravy and seasoning mixes
Cookies and crackers
Cured meats
Smoked meats and sausages
Diet foods
Freeze-dried foods
Frozen foods
Potato chips
Prepared snacks
Prepared salads, salad dressings, and mayonnaise
Croutons
Bottled and canned sauces
Spices and seasonings
Glutamate is also present in monopotassium glutamate, monoammonium glutamate, calcium glutamate, and other salts of glutamic acid. Some Monosodium glutamate-sensitive persons may react to these salts also. Look for these terms on food labels.
Restaurants, Cafeterias, and Fast-Food Restaurants
The majority of eating places in North America include Monosodium glutamate in some form in most of their dishes, unless they specifically state otherwise. However, most reputable establishments can supply a list of the ingredients in their menu items.
Avoiding Monosodium glutamate
Table The Monosodium glutamate- restricted diet provides you with guidelines to avoid added Monosodium glutamate in your food and to reduce your intake of natural forms of glutamate.
Table The Monosodium glutamate- restricted diet
| Type of Food | Foods Allowed | Foods Restricted |
| Milk and Milk
Products |
• Plain milk, buttermilk, cream,
sour cream, and yogurt • All plain cheese, cottage cheese, ricotta, Quark • Pure vanilla ice cream • Plain salted or unsalted butter |
• Flavored milk
• Commercial dips • Flavored yogurts ‘ All flavored and smoked cheese, cheese slices, and cheese foods • All other ice cream • All seasoned butter |
| Breads and
Cereals |
• Any pure flour or grain
• Any bread, bun, pita or pizza dough without flavoring, except plain sourdough |
• Bread, baking mixes, or grain mixes
with flavoring or seasoning packets • Sourdough bread and buns • All others, such as croutons, stuffing, meat coating mixes |
| • Breakfast cereals without
flavorings, including - Puffed rice and wheat - Shreddies - Shredded Wheat - Corn flakes - Cereals with malt or malt syrup - Pats and oatmeal - Plain Cream of Wheat - All plain grains |
• All others, especially the colored and flavored cereals made to appeal to children
Flavored oatmeal and Cream of Wheat |
|
| • Plain crackers without
flavoring • Plain pasta • All homemade baked goods, cereals, and pasta dishes with allowed ingredients |
• All flavored crackers
• All flavored pasta • All canned, frozen, and dried commercial pasta dishes |
|
| Vegetables | • All pure fresh and frozen
vegetables and their juices |
• Canned vegetables and juices
• Read labels on plain frozen vegetables. • Commercially prepared vegetables with sauces and flavorings |
| Fruit | • All pure fresh and frozen fruits
and their juices • Homemade fruit dishes and drinks with allowed ingredients |
• Fruit dishes with flavoring
• Fruit drinks and cocktails |
| Meat, Poultry,
and Fish |
• All unprocessed pure, fresh,
or frozen meat, poultry, or fish • Fish canned with water or with water and only salt • Processed meat such as ham, with “Monosodium glutamate-free” on the label • Homemade sausages, etc. |
• Processed or with restricted
ingredients, e.g.: - Stuffing - Butter-basted in broth with spices or seasoning • Cured or smoked sausages, patties, etc. • Canned, except as listed at left |
| Eggs | •All | • All prepared with restricted foods |
| Legumes | • All plain legumes
• Pure peanut butter |
• All others |
| Nuts and Seeds | • All plain nuts and seeds | • All others |
| Fats and Oils | • Pure butter and cream
• Shortening • Pure vegetable oils • Homemade salad dressing • Lard and meat drippings • Gravy |
• All others |
| Spices and
Herbs |
• All fresh, frozen, or dried
herbs and single spices |
• All herb or spice mixes and
seasoning packets • See listing of flavorings containing Monosodium glutamate on page 316. |
| Sweets and
Sweeteners |
• Sugar, honey, molasses
• Pure jams and jellies • Pure corn and maple syrup • Plain artificial sweeteners • Homemade sweets and fruit drinks with allowed ingredients |
• Artificially flavored and colored
sweeteners, jams, jellies, icings, cake decorations, candies, and drink mixes |
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