It has become extremely difficult to find unadulterated food. Unless you are fortunate enough to be self-sufficient in your food production, as my family was when I was young, you are being exposed to an untold number of food additives and preservatives daily.

A food additive is defined as "any substance the intended use of which results or may reasonably be expected to result, directly or indirectly, in its becoming a component or otherwise affecting the characteristics of any food." Food additives are used for many reasons. They are often used in food processing. They may improve packaging safety or facilitate transportation. Most are used to enhance flavor or texture, prevent spoilage or discoloration, and extend shelf-life.

A number of food additives do not need to be listed on the product’s label because they are considered “indirect” additives. Indirect additives are substances that are used in food processing, but which are not considered part of the final product. For example, antimicrobial agents are commonly used in meat packaging to retard the growth of bacteria. These are not added to the meat or poultry directly, but some residue inevitably remains on the product when it is prepared and eaten. Direct food additives are often not listed by name, but simply by general terms such as “natural flavor”, “artificial flavor”, or “anti-caking agents.”

According to the United States Food and Drug Administration (FDA), over 3,000 approved food additives exist. While some are common substances like salt, sugar, or herbs, many are complex chemicals. Little is known about the long-term effects of many approved food additives. A number have been withdrawn over time because they have been found to be carcinogenic (cancer-causing) or have other adverse effects.

Of all the food additives used in the United States none has been more maligned and criticized than monosodium glutamate (MSG). A Google search of “monosodium glutamate dangers” produced 38,000 results, “monosodium glutamate side effects” elicited 58,500 listings, and “monosodium glutamate risks” produced a whopping 771,000 links. Titles of the links were ominous: “MSG – Slowly Poisoning America”, “The Shocking Dangers of MSG”, and “A Sure Way to Cause Brain Damage.”

What is MSG, why is it added to foods, and is it as dangerous as many claim it to be? To answer these and other questions we must start with the sense of taste.

When asked to name the tastes that can be distinguished by the human tongue most people will list sweet, sour, salty, and bitter. There is, however, a fifth taste sensation. It is usually called umami, although some refer to it as savoriness. Umami is a Japanese word meaning “good flavor.” It was first identified in 1907 by Kjkunae Ikeda, a Japanese scientist who was studying the characteristics of seaweed broth. He discovered that the broth’s unique taste was due to the amino acid glutamate and he subsequently developed and patented monosodium glutamate. Monosodium glutamate is actually a cousin to table salt, sodium chloride, which could be called monosodium chloride.

Although umami was ignored in the west throughout most of the twentieth century (some people today continue to deny its existence claiming that it is an imaginary taste created solely to promote the use of MSG) it is present in a number of foods commonly consumed in the United States and Europe. It is most pronounced in bacon, but it is present to some degree in most meat products. The key substance for generating umami is glutamic acid (glutamate), which is present in significant amounts in beef, lamb, parmesan and roquefort cheese, mushrooms, ripe tomatoes, soy sauce, Oriental fish sauce, and Worcestershire sauce. Glutamate is also found in seafood such as lobster, crab, and shrimp and, to a lesser degree, in most other protein containing foods.

It is actually quite difficult to find foods that do not contain some amount of glutamate. I found a listing on the website msgtruth.org. A glutamate-free diet would consist almost exclusively of greens and root vegetables, and would provide little variety. It would not contain any significant protein source, and it would be difficult, if not impossible, for a person to remain healthy over time on such a diet.

If umami is a taste that is pleasurable and glutamate is present in nearly all protein-containing foods why is MSG viewed with such alarm? The answer is related to the role of glutamate in the body.

Glutamic acid or glutamate is a key molecule in cellular energy production. It also plays a major role in eliminating excess nitrogen from the body. One of its most important roles, however, is acting as a neurotransmitter, facilitating the flow of signals throughout the nervous system, including the brain. As the most abundant excitatory neurotransmitter in the brain, glutamate plays a key role in facilitation of learning and memory.

Glutamate is absolutely essential for proper brain and nervous system function. The challenge lies not in the presence of glutamate in foods, but in excessive amounts of glutamate in the diet. Because MSG provides a concentrated source of sodium and glutamate in much the same way as table salt provides a concentrated source of sodium and chloride, excessive amounts may produce undesirable effects.

Some of the adverse effects are due to the intake of excessive amounts of sodium. Just as eating foods high in salt can result in fluid retention, so can consumption of foods high in MSG. Most people can remember feeling puffy following a meal at an Oriental restaurant. This was due to the high sodium load that resulted from the addition of MSG to various foods.

The adverse effects most commonly attributed to MSG include numbness, tingling, or burning sensations, facial pressure or tightness, chest pain, headache (typically migraine), nausea, rapid or irregular heartbeat, drowsiness, weakness, and aggravation of asthma symptoms.

Because glutamate excites the nervous system it is logical that anxiety and panic attacks can be associated with MSG intake. MSG can also increase the likelihood of a seizure occurring in susceptible individuals. Excitement of the digestive tract can lead to abdominal cramping and diarrhea. I have, however, seen articles and websites that attribute nearly every known symptom to MSG use. The connection of most of the symptoms listed to MSG is unsubstantiated and claiming that they are due to the use of MSG is irresponsible.

Some sites proclaim that MSG can cause blindness. This statement is based upon a 2002 Japanese study that found that rats in which MSG made up 20 % of their diet were prone to thinning of the retina of the eye. A few studies in which MSG was injected directly into the eye showed similar results. These studies, however, do not accurately portray what is likely to happen to someone who is getting a typical dietary exposure to MSG. To suggest that someone who consumes foods containing MSG will go blind is unwarranted.

There is an aspect of MSG sensitivity that is almost universally overlooked by those crusading against use of the substance. It is quite possible that MSG is not the perpetrator, but the messenger. There is good reason to believe that the leading cause of MSG sensitivity is vitamin B6 deficiency. The relationship between vitamin B6 deficiency and impaired monosodium glutamate metabolism was noted in animals in the 1970s. A 1984 study found that 8 out of 9 people with MSG sensitivity stopped reacting to MSG-containing foods within 3 months when supplementing B6 50 mg. daily. Ironically, 25 years later the focus remains on the evils of MSG rather than on the real issue, which is widespread vitamin B6 deficiency.

The possibility that MSG may not be the four alarm fire so many claim it to be, but rather a smoke detector unmasking vitamin and mineral deficiencies is further suggested by the conditions that are adversely affected by MSG consumption. Multiple sclerosis, autism, and attention deficit hyperactivity disorder (ADHD) are known to be improved by supplementation of B vitamins. Irritable bowel syndrome is often characterized by low vitamin B levels. Asthma and diabetes are aggravated by low magnesium levels. Correction of deficiencies in B vitamins and magnesium brings improvement in conditions that are most aggravated by MSG intake.

A careful analysis of MSG sensitivity reveals that a challenge with MSG arises primarily in two situations: 1)if it is consumed in combination with aspartame (NutraSweet), which dramatically increases the amount of glutamate reaching the brain, and 2) when deficiencies of B6, magnesium, and zinc are present. When one has optimum levels of those nutrients, metabolism of glutamate proceeds smoothly and excess amounts do not accumulate. The bottom line is this: I wouldn't intentionally add MSG to my food, but I'm not going to stress out about whether it's present in small amounts in processed foods or in those I’m served when I'm eating out.