What if your gluten intolerance is all in your head?

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For many sufferers, gluten intolerance may originate in the mind, not the body. But that's nothing to be ashamed of, says a philosopher

While living in China from 2003 to 2005, I often served as the designated translator for fellow expatriates. Whenever we ate out, this involved asking our server which menu items contained monosodium glutamate (MSG). Invariably I was told that almost everything is made with weijing ("flavour essence"), including, on one occasion, the roast peanut appetiser my MSG-sensitive friends were snacking on as I made my enquiry.

After observing that no one reacted to the peanuts, I was inspired to conduct a simple (and admittedly unethical) experiment. One evening, instead of translating honestly, I told my companions at a large banquet that the kitchen had promised to avoid using MSG. Everyone thanked me and happily ate their meal, dish after poisoned dish.

An hour later? Two hours later? The next day? Nothing.

I repeated this experiment on multiple occasions, always with the same result. And yet foreigners living in China routinely complained of reactions to their food that included headaches, chest pain and shortness of breath. Was there something about my presence that conferred temporary resistance to MSG? Or could it be that MSG sensitivity was only in their heads?

Chinese restaurant syndrome

In April 1968, the New England Journal of Medicine published a letter by Robert Ho Man Kwok that described a strange set of symptoms: "Numbness at the back of the neck, gradually radiating to both arms and the back, general weakness and palpitation." Stranger still was the fact that Kwok, himself a Chinese immigrant, typically noted the onset of these symptoms 20 minutes after eating at restaurants serving "Northern Chinese food".

An editor at the journal titled Kwok's letter "Chinese restaurant syndrome", and thus began a minor epidemic. For countless sufferers, a mystery had been finally solved. "No MSG" signs sprang up across the US, and, eventually, the world. Study upon study confirmed the syndrome's existence and speculated about the science underlying it.

But after reading some of these studies, even a layperson will start to get suspicious. Take the editorial note that precedes Russell Asnes's article "Chinese restaurant syndrome in an infant": "The evidence that this infant had the Chinese Restaurant syndrome may be only circumstantial. However, the description of the symptom is accurate as attested to by the Editor's wife who suffers from the same malady. Incidentally, she remains a devotee of Chinese cuisine."

Science, that sworn enemy of circumstantial evidence, marched on, and slowly but surely physiological explanations of Chinese restaurant syndrome began to lose credibility. Double-blinded studies failed to turn up evidence of a clinical condition. MSG, many people noted, appears in everything from sushi to Doritos. Journalists performed experiments similar to mine, their results echoing the consensus of professional scientists: in the overwhelming majority of cases, MSG sensitivity is a psychological phenomenon.

Despite this thorough debunking, a surprisingly large number of people ? generally those who lived through the epidemic ? still insist they are sensitive to MSG. Google around and you'll turn up scores of alarmist websites, which tend to combine outdated research with anecdotal, indignant rebuttals of the current scientific wisdom: "How dare you suggest my MSG sensitivity is only in my head? Why, just the other day I went out for Chinese and forgot to ask about MSG. After 45 minutes I couldn't breathe and my heart was racing."

Occasionally, as with vaccines and climate change denial, alarmism veers into paranoia, yielding accusations that a shadowy east Asian cabal is paying off scientists and journalists to regurgitate their propaganda. (Ajinomoto Corporation, I await your cheque!). For a small minority, MSG sensitivity somehow became more than a medical condition, and challenging its physiological basis poses a threat to their very identity. The harmfulness of MSG, a seemingly trivial assertion, took on the importance of a religious doctrine, a fundamental truth to be defended at any cost. But why?

Gluten rising

In 2007, my wife's cake shop did not offer a gluten-free option. Six years later, hardly a month goes by without a request for a gluten-free tasting. Thanks in part to celebrities such as Oprah Winfrey and Lady Gaga, nearly one-third of all consumers are now interested in gluten-free food, a multi-billion-dollar industry projected to exceed $10 billion by 2017. (Even children's play sand now comes with a gluten-free guarantee!)

This is very perplexing, given that only 1 per cent of the population has coeliac disease and only 0.5 per cent is allergic to wheat. What could possibly be causing widespread reports of non-coeliac gluten intolerance, commonly blamed for a raft of symptoms including gas, bloating, diarrhoea, constipation, fatigue, goose bumps, dizziness, infertility, migraines, joint inflammation and even mood disorders?

Scientists are applying themselves to the riddle, and last February Slate's Darshak Sanghavi reported on an Italian study that confirmed the existence of gluten intolerance ("non-coeliac wheat sensitivity") as a third, "distinct clinical condition". In the study, one-third of patients who self-identified as gluten-intolerant did in fact experience symptom relief after adopting a gluten-free diet. Case closed, right? Pass the gluten-free pasta.

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