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 neurobiologist 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 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, common American foods contain MSG; such as:
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 have shown no link between MSG and Chinese Restaurant Syndrome, some American consumers have stopped eating MSG out of the belief that it is harmful. Some restaurants have since promoted themselves as MSG-free places to eat.
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.