MSG under the microscope: what food science reveals about a misunderstood additive

Monosodium glutamate (MSG) is the sodium salt of glutamic acid, a naturally occurring amino acid. “Mono” refers to one sodium ion, which is bound to glutamate to form a stable crystalline compound used as a flavour enhancer. Glutamate is found naturally in foods such as tomatoes, cheese and mushrooms, and it contributes to the savoury taste known as umami. In the late twentieth century, reports of mild symptoms after restaurant meals in the USA led to concern about MSG, often unfairly linked to Chinese cuisine through the term “Chinese Restaurant Syndrome”. However, controlled studies have found no consistent evidence that MSG is harmful at typical dietary levels, and major health authorities consider it safe for the general population.

Kikunae Ikeda, a Japanese chemist, invented MSG in 1908 as he believed there were more than four basic flavour profiles (sweet, sour, bitter and salty). He isolated glutamate from dried kombu seaweed (kelp) but found that alone it was unstable and hard to use and so combined it with sodium, making MSG. Glutamate is a common amino acid which is present in many different foods including parmesan, tomatoes, dried mushrooms, soy sauce and human breast milk. Ikeda went on to make Ajinomoto, a MSG-based condiment, which exploded in popularity in Japan and then China. 

In 1968, Dr Robert Ho Man Kwok wrote a letter to the New England Journal of Medicine detailing a syndrome he experienced after eating at Chinese restaurants in America. He described feeling a numbness in his neck which spread to his arms and back. He suggested that it could be from MSG, which sparked media attention, leading to fear and anxiety around the use of the ingredient. Despite the use of MSG in canned soups, processed meats and frozen meals, people often chose to draw focus on Chinese food, contributing to harmful racial stereotypes. 

Studies were performed but struggled to provide consistent results that MSG causes side effects. Some studies used participants who knew they were consuming MSG, leading to bias, whilst others used unrealistic doses of MSG without food which does not accurately reflect the use of MSG in a meal. The US Food and Drug Administration (FDA) and the World Health Organisation (WHO) both confirmed that MSG is safe to consume, although some people may experience mild symptoms which are short-lived. These effects are most commonly reported when large quantities of MSG are consumed on an empty stomach, rather than when it is eaten in typical amounts as part of a mixed meal.

These persistent myths about MSG not only contradict scientific evidence, but also perpetuate enduring racial and cultural stereotypes in society.