So many people report feeling unwell after eating too much Asian food -- most often Chinese food -- that a term was coined for the feeling: the Chinese Restaurant Syndrome.

Is the fatigue and headache you experience after indulging at a Chinese buffet caused by MSG, or could it simply be a matter of eating too many foods -- often fried in heavy oil -- in one setting?

Exactly What is the Chinese Restaurant Syndrome?

The term first appeared in 1968 in the New England Journal of Medicine to describe the general feeling of unwell that people feel after eating certain Asian foods.

Monosodium glutamate, commonly known as MSG, is most often blamed as the cause for Chinese Restaurant Syndrome, however, numerous studies over decades have failed to confirm that normal amounts of MSG cause the effects claimed.

Even still, a large number of Westerners have stopped eating Chinese food because of the way they feel afterward.

Symptoms of Chinese Restaurant Syndrome

People sometimes report the following symptoms after consuming too much Chinese food:

• Lethargy
• Headache
• Sweating
• Extreme thirst
• Chest pain and tightness
• Flushed face

Is Chinese Restaurant Syndrome Real?

While many point the finger at MSG, advocates of the food additive claim that the general feeling of unwell is because people overindulge at Chinese buffets, often mixing cheap and difficult-to-digest foods fried in heavy oil. People who believe they are allergic to MSG almost never claim the same headaches after eating lunch meats or popular-brand soups that often contain MSG.

An Australian study of 71 volunteers who were convinced that they were sensitive to MSG were given a mix of real MSG tablets and placebos.

Subjects given real MSG reported no ill effects, while those that were given placebo tablets reported the same syndromes that they felt after consuming Chinese food.

MSG has been shown to increase appetite by making foods taste more appealing and to effect the body's natural appetite-suppression system, hence the symptoms of Chinese Restaurant Syndrome may simply be a result of overeating heavy foods!

What is MSG?

Glutamate is an amino acid that occurs naturally in every living food, from vegetables and meats to breast milk. Monosodium glutamate is the sodium salt derived from fermenting glutamic acid. Sushi seaweed (nori), Parmesan cheese, mushrooms, and even tomatoes all get part of their unique tastes from higher levels of natural glutamate.

MSG is most often confused as a preservative, however, it is actually a salt that rounds and balances the flavors already present in food. While glutamate is not laboratory-produced and does occur all throughout nature, the quantities consumed when it is used as a food additive in the form of MSG are not natural. MSG is essentially a manufactured, concentrated version of what makes certain foods taste good in the first place, added back those same foods.

Proponents of MSG claim that the body cannot tell the difference between monosodium glutamate and naturally occurring glutamate.

Monosodium glutamate is most often associated with Chinese food, perhaps unfair because MSG was actually discovered by a Japanese professor at the University of Tokyo in 1907. He named the savory flavor that MSG produced: umami. In 2002, scientists discovered that we do indeed have specific receptors on our tongue for the savory sensation that glutamate produces and officially added umami (savory) as a fifth taste to go along with sweet, salty, sour, and bitter.

Today, MSG is liberally added to food and snacks in Japan, China, Korea, India, and Southeast Asia. Even a majority of popular Western brands use the flavor enhancer in meats and processed foods.

• Read more about Southeast Asian cuisine.

Is MSG Safe?

The debate over MSG's safety has been raging for decades, making it one of the most studied food additives in history. Despite at least 60% of the world's population in Asia purposefully consuming MSG daily, the acronym has practically become a dirty three-letter-word in the West. While Westerners pay more for pet foods that claim to be MSG free, Asians buy the powdery substance in five-pound bags and sprinkle it into as many dishes as possible.

Extensive studies on the effects of MSG have been conducted since 1959, eventually leading to the FDA, European Union, United Nations, and World Health Organization all listing MSG as a safe food ingredient. An additional study by the European Union declared that MSG was proven safe for both infants and pregnant women.

In 2008, a collaborative of Chinese and American researchers linked MSG with obesity, however, a Chinese study in 2010 proved the opposite. It was later suggested that the enhanced flavors in food tempt people into overeating and the thirst that MSG -- a salt -- causes is often quenched with alcohol or sugary drinks, leading to weight gain.

Japan -- the leading per-capita consumer of MSG -- boasts the world's longest life expectancy as well as the world's lowest obesity rate!

While sodium chloride (table salt) is also manufactured and remains widely accepted, it's also a major contributor to high blood pressure which can cause heart disease -- the leading cause of death in the world. MSG actually contains three times less harmful sodium than table salt and less MSG is needed than salt to season food while cooking.

Avoiding MSG in Asia

When one noodle vendor in Chiang Mai, Thailand, was asked why he used MSG in his food, he simply replied, "because I have to." In other words, with all his competitors using MSG to enhance the savory taste in foods, he was forced to do the same to compete. MSG turns up in most street food in Asia.

Some organic cafes and restaurant owners have caught on to the anti-MSG trend in the West and now advertise 'NO MSG' with signs to attract health-conscious travelers. This may or may mean that their food is free of MSG. Even if they don't purposefully add MSG to dishes, many of the ingredients and seasonings (i.e., soy sauce, oyster sauce, and tofu) they use to prepare food already contain the substance.

MSG is often substituted for salt in Asian food -- even the salt shaker on your table and the soy sauce you use probably contain MSG.

MSG in Western Food

Don't think for a second that MSG is only used in Asian food. Many Western snacks, canned foods, deli meats, and soups contain MSG as a flavor enhancer. In the European Union, Australia, and New Zealand, monosodium glutamate shows up on food labels as 'E621'. The acronym is not allowed on food labels in the US; food makers must label 'monosodium glutamate' as an additional ingredient not included generically with 'seasonings and spices'.

People who truly believe that they are allergic to MSG are most likely also sensitive to glutamic acid and its salts in general. Glutamic acid can be present in foods listed as containing:

• hydrolyzed vegetable protein
• autolyzed yeast
• hydrolyzed yeast
• yeast extract
• soy extract
• protein isolate
• hydrolyzed protein.

Hydrolyzed proteins are proteins that have been broken apart chemically into their amino acids which may then form free glutamate. Free glutamate can bond with sodium that is already present to create MSG in foods; when this occurs, foods are not required by law to be labeled as containing MSG.

Interestingly, MSG eaten alone tastes unpleasant when there is no food to enhance!