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DURING my master’s degree, I lived high up in the mountains of rural Ecuador, studying the practices of traditional Andean medicine. I was fascinated by beliefs of culturally specific syndromes, like susto, thought to be caused by spiritual attack, resulting in insomnia, depression and anorexia, or mal de ojo, in which a stare from another person can cause severe fever, diarrhoea and even death in children.

What always stood out when I asked about the basis of these ideas was that the explanations seemed far-fetched to me but common sense to them. That is the thing about culture: to the people enveloped in it, even beliefs that defy explanation can seem like unquestionable reality. Ours is, unsurprisingly, no exception. To illustrate this, let’s look at the evidence supporting what is arguably one of the West’s culturally specific syndromes: “Chinese restaurant syndrome”.

Coined in the US in the 1960s, it describes a constellation of symptoms such as numbness, palpitations and nausea that are thought to occur after consuming the food additive monosodium glutamate (MSG), often associated with East Asian restaurants. This belief is so pervasive that it has been propagated in bestselling books, espoused on blogs and has even led many restaurants to advertise food as “MSG free” to avoid a backlash. So what could be behind this worrying reaction?

Well, as I found when talking to Andean communities, the exact explanation for beliefs can vary dramatically depending on who you ask. Some cite the fact that MSG doesn’t exist in nature, others its synthetic means of production, or even its “unpronounceable” scientific name. Still others cite the fact that scientific trials clearly prove its toxicity. However, perhaps surprisingly, when we look at the evidence, none of these “facts” is really a fact.

While it is true to say that since as early as 1969 studies have reported startling symptoms such as stunted skeletal development, marked obesity and female sterility associated with MSG, it is . You might be forgiven for thinking that scientists set up a clinical trial, in which they fed unfortunate volunteers MSG-laced food and witnessed the terrible effects. This wasn’t the case. These studies actually involved doing things like injecting enormous doses of the compound into newborn lab mice. Many harmless compounds found in all sorts of foods, including key nutrients, would probably show similarly undesirable outcomes in a similar set up.

“This belief is so pervasive it has even led many restaurants to advertise their food as ‘MSG free’”

If you take such poor-quality studies out of the equation, and focus on human clinical trials, you are presented with a different picture. One of the earliest was carried out in the 1990s, on a . They were fed randomly assigned meals with varying levels of MSG, including a placebo, and then asked about their reactions. Around 36 per cent of them did indeed report these effects after a meal containing a threshold of about 2.5 grams of MSG. However, around 30 per cent of them had no reaction to any meal, including placebo. A difference of 30 per cent to 36 per cent can still be statistically significant with enough participants, but in this study we are only comparing 18 people with 22.

How much MSG is there in a typical serving of food containing the compound? According to the US Food and Drug Administration, 0.5 grams, meaning that to get the results in the study, you would have to eat five times the average serving in one go. Even in countries like Japan, where daily consumption of MSG is among the highest on the planet, the amount eaten daily has been estimated at between 1.2 and 1.7 grams. I am game for the experiment of eating two days’ worth of Japanese food in one meal, but even for me that might be hard to achieve.

What of concerns about the “synthetic” nature of this food additive? Well, in actuality, MSG is naturally found in all sorts of foods eaten in the West, like cheese and tomatoes. In fact, the glutamic acid, the alleged problematic component, is even produced by our own bodies.

The MSG in food additives is made by fermenting plant extracts like tapioca or sugar-cane molasses using naturally occurring bacteria, which makes calling it “synthetic” a stretch.

So does Chinese restaurant syndrome count as a culturally bound syndrome? Well, although the scientific consensus is pretty resounding, it is also fair to say that the studies to date are few in number and, in some instances, contradictory. Indeed, many food intolerances once dismissed on the basis of poor evidence are now being taken more seriously. So I, for one, can’t wait to learn what new evidence turns up.