Despite what some of its opponents have long claimed, Monosodium Glutamate (MSG) may have nothing to do with those headaches you get after eating Chinese food, and may not be bad for you at all.

A post by Alan Levinovitz in New Scientist brought to our attention the data showing that MSG sensitivity is, for most people, only in their heads.

Despite the persistent absence of any scientific evidence, some people claim to suffer from a sensitivity to the food additive, which is used in everything from Asian cuisines, to American fast food and packaged snacks.

Sufferers describe symptoms such as headaches, feeling flushed, and sweating after eating food containing the additive according to Mayo Clinic nutritionist Katherine Zeratsky.

Any symptoms they claim to experience are mild, don't require an ambulance, and don't seem to have lasting effects. Others seem to only show symptoms when they know they are eating MSG — suggesting it's a placebo effect.

What is MSG?

MSG stands for Monosodium Glutamate, the key compound of which is the latter, glutamate. Glutamates occur naturally in various types of seaweed and fish, and are often credited with being responsible for their "umami" flavor.

The word "umami" was coined by Japanese scientist Kikunae Ikeda in the paper where he discussed glutamates as the chemical source of the meaty, savory flavor previously unknown to scientists.

After isolating the glutamate, he stabilized it by making it a salt by adding a sodium ion (hence the "monosodium" prefix), patented the whole thing and made a fortune through the company he founded, Ajinomoto Corporation.

Levinovitz admits in his New Scientist piece to conducting a mischievous, not totally scientific experiment. He lied to his traveling companions in China who claimed to have MSG sensitivities, about the MSG content of their meals. He then waited to hear of their horrible reactions.

But there was no outcry, even when the food contained MSG. His friends happily ate "dish after poisoned dish," and never complained of the headaches, "numbness at the back of the neck, gradually radiating to both arms and the back, general weakness and palpitation," that people attribute to consumption of MSG.

The mounting evidence

Since concerns over MSG first entered popular consciousness in the late 1960s, tons of scientists have attempted and failed to prove any real danger to the additive.

Double-blind studies of MSG's effects on the body have not turned up any of the symptoms people sometimes report, including one published in the February 1971 issue of the Journal of Toxicology and Applied Pharmacology.

Nevertheless, complaints of side effects abound, ranging from merely inconvenient headaches to what About.com's Danilo Alfaro, after eating at a favorite Korean restaurant, described his reaction as "head pounding, ears ringing, heart racing so fast I could see it thumping through my shirt. Also, I had a murderous thirst and had sunk into what I can only describe as a deep malaise (which, considering these other symptoms, really isn't much of a surprise)."

Wow. Sounds pretty intense.

Danilo did what a lot of people do: He researched his symptoms on the Internet. "This wasn't my imagination and it wasn't a coincidence. A quick Google search confirmed my suspicions: I was in the grips of a wicked case of MSG Sensitivity Syndrome."

While there is a chance Alfaro's self-diagnosis is correct, it's more likely he was a bit too quick to blame his symptoms on MSG. That's especially true since Danilo said it was his favorite restaurant — which would mean he'd eaten there before.

Most people who have an intense reaction like this to what they think is MSG are likely suffering an allergy to another ingredient, according to Merlin Thomas, a doctor with the Baker IDI Heart and Diabetes Institute in Melbourne, Australia. People sometimes encounter MSG when they are eating foods unfamiliar or exotic to their usual diet, and misconstrue an allergy to another unusual ingredient as an MSG attack.

Allergic reactions occur when the body treats normally harmless substance as an invader or toxic substance. The immune system fights the invader, producing the reaction, which can range from mild sickness or a skin rash to severe choking or shock.

Doctors can check for allergies by looking for specific antibodies against the allergen.

But, "no such antibodies or reactions are observed with MSG," Thomas told Business Insider in an email. "So whatever people experience, it is not a food allergy, unless they are allergic to something else in the meal that they are not normally exposed to. Typically such allergic reactions will first will occur in a foreign country or restaurant when eating food they don’t normally eat at home."

So what's the problem?

What may matter more is not if a food contains MSG, but how we are eating it.

MSG mixed thoroughly into a dish is much different from MSG sprinkled on top. Hastily dusting it onto a dish will concentrate a full portion of the additive in a few places — sort of like spicing a dish with whole chili peppers instead of spreading it throughout the dish. Some mouthfuls are going to have much more MSG in them than others.

Sprinkled on top of a dish, even a normal "dose" of MSG could be taken in in just a few bites — and could overload your system, the same way eating a spoonful of salt or sugar would.

Our stomachs contain glutamate receptors that help eventually activate the vagal nerve. The vagal nerve reports to the brain on the health of the intestine and helps us determine things like how hungry we are and whether we have eaten enough to be full.

It also oversees nausea and vomiting. An unnaturally high concentration of MSG (or, many other things) could confuse these receptors into thinking we are either eating too much or ingesting something toxic, which might cause a reaction.

But the MSG itself, in recommended doses, is not dangerous at all, and health professionals like Thomas are concerned that scapegoating individual ingredients masks what are really larger problems of poor diet and food quality.

"There have been calls to ban MSG from food products or to be clearly labeled. But no one has thought to ban Parmesan cheese or Vegemite," said Thomas. "Moreover, nutritional labeling is often misconstrued. Being MSG-free is not the same thing as being healthy, much the same way that products high in processed carbohydrates can be labeled as being low in fat or salt."

Not just Chinese food

MSG is often thought to be found primarily in packaged snack foods and in some Chinese food. But the additive in its natural and manufactured forms is everywhere and can be found in many different cuisines, through sauces, Parmesan cheese, bouillon cubes, and other ingredients. Even some of the world's most elite restaurants feature glutamates in their dishes.

Natural glutamates are found in all kinds of foods we eat, including asparagus, meat, tomatoes, and mushrooms, and are even abundant in breast milk. Japanese cooks have been soaking or boiling dried fish or a few leaves of kombu seaweed to make the broths used in classic dishes like ramen noodle soups, infusing the broth with glutamates and giving it its rich, savory flavor.

The ingredient made its way into the American diet largely through the packaged and canned foods that often lost a lot of their flavor during processing.

Chinese Restaurant Syndrome

The origin of the MSG scare was a "paper" published in the New England Journal of Medicine in 1968 by a scientist named Robert Ho Man Kwok, who said he felt certain symptoms after eating at Northern Chinese restaurants. "Chinese Restaurant Syndrome" was born.

A few more sensational studies were performed, that mostly involved feeding staggering amounts of the stuff to lab mice, but real research connecting normal, and even larger-than-normal, doses to adverse effects has yet to surface.

"The consensus among clinicians and scientists is that MSG is safe for human health," Thomas said. "Very high doses or highly concentrated applications may affect some people for a short time."

In the end Thomas is much more worried about other parts of our diets than the MSG: ".[T]here may be far more dangerous consequences that come from overeating, and banning MSG is not the simple solution. It is far better to encourage people to eat fresh, whole, and local food instead. Tastes great and it requires no MSG."