Chinese restaurant syndrome

Chinese restaurant syndrome, also called monosodium glutamate symptom complex, is a collection of symptoms which may include headache, flushing, sweating, and a sensation of pressure in the mouth or face. It is commonly believed that monosodium glutamate (MSG) is the cause, but repeated scientific studies have shown no link.

Less common, but more serious symptoms attributed to the syndrome have included swelling of the throat, chest pain, heart palpitations, and shortness of breath. Most people recover from mild cases of Chinese restaurant syndrome with no serious harm. Symptoms of CRS can be eliminated by supplying a normal amount of vitamin B6 before consuming a meal rich in MSG.

According to Steven Rose : "The most common excitatory transmitter in the brain is the amino acid glutamate. [...] Glutamate also serves as a food flavouring in some cuisines, notably Chinese and Japanese, but if it is taken in excess in such diets, it can act as a neurotoxin by over-exciting glutamatergic synapses in the brain, [...] the so-called 'Chinese restaurant syndrome'."

The term
In the 1960s some Americans who ate at Chinese restaurants later noticed an irritation. Symptoms included drowsiness, tingling, headaches, and slight numbness on the back. The large majority of these symptoms were benign, and went away after a while. The phenomenon soon got the name "Chinese restaurant syndrome".

The synonym "monosodium glutamate symptom complex" originated from the observation that monosodium glutamate (MSG) was often used in Chinese restaurants in the United States. MSG is a common flavor enhancer, used in a wide variety of processed foods and recipes made at restaurants and homes in many cuisines. The name "Chinese restaurant syndrome" refers to the initial discovery of the phenomenon, but Chinese restaurant food is not the sole source. Indeed, MSG is contained in many common American foods, including:
 * most canned soups of the US food industry, such as Campbell's Soup (except the low sodium varieties)
 * most beef and chicken stocks of the US food industry, such as Swanson's (except the low sodium varieties)
 * most flavored potato chip products of the US food industry, such as Doritos(except Natural White Cheese and Toasted Corn Tortilla chips)
 * many other snack foods
 * many frozen dinners
 * instant meals such as the seasoning mixtures for instant noodles.

MSG is a natural ingredient chemically derived from plants, such as kombu seaweed, used in traditional East Asian cuisines, so the material became a part of Chinese and other Asian dishes. Factory-made MSG was first created in Japan in the early 1900s by Dr. Kikunae Ikeda, who later formed the first MSG manufacturing company, Ajinomoto, Co. In World War II, American soldiers were amazed at how much better the Japanese rations tasted, and the US military investigated, finding MSG to be the cause. By the early 1950s, many major US food companies such as Pillsbury, Campbells, Oscar Mayer, Libby, General Foods, and more, were using MSG in their processed foods, and MSG was becoming available in pure form on supermarket shelves. Today, Ajinomoto remains the world's largest manufacturer of MSG.

Although multiple studies prove no link between MSG and so-called Chinese Restaurant Syndrome, some American consumers have stopped eating MSG out of the belief that it was harmful. Some restaurants have since promoted themselves as MSG-free places to eat.

Scientific controversy
Despite the general perception that MSG is the causative agent of Chinese restaurant syndrome, studies have been inconsistent in demonstrating a specific syndrome associated with MSG. A double-blind placebo-controlled crossover trial showed that large doses of MSG taken without food may cause symptoms, but the effects were not serious, persistent, or consistent. Moreover, when MSG was given with food, the effects were not observed.

Instead of assigning the syndrome to one specific cause, one scientific review suggests that the Chinese restaurant syndrome is a name applied to a variety of illnesses which occur after eating, each of which may have independent causes.