Despite its extreme toxicity, puffer fish is a famous delicacy in Japan, where it is called fugu. Preparing fugu is a job entrusted to only a few specially trained chefs, who must carefully remove the fish’s liver, intestines, and skin before cooking because they are particularly saturated in poison. Even then, enough toxin remains to numb the mouth and leave the diner feeling pleasantly woozy. In one famous case in 1975, a well-known actor named Bandō Mitsugorō ate four helpings of fugu—despite pleadings to stop—and died wretchedly four hours later of asphyxiation. Fugu still kills about one person a year.
The difficulty with fugu is that by the time the ill effects become evident, it is much too late to do anything about it. The same is true of all kinds of other substances, from belladonna, or deadly nightshade, to a wide range of fungi. In 2008, in a widely publicized case, the British author Nicholas Evans and three members of his family became deathly ill on holiday in Scotland when they mistook a deadly mushroom, Cortinarius speciosissimus, for its benign and delicious cousin cèpe. The effects were horrific—Evans needed a kidney transplant, and all members of the party suffered lasting damage—yet nothing in the taste alerted anyone to the perils ahead. The fact is, our putative defenses are far more putative than defensive.
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We have about ten thousand taste receptors, but we actually have more pain and other somatosensory receptors than taste receptors in our mouths. Because they exist side by side on the tongue, we sometimes mix them up. When you describe a chili as hot, you are being more literal than you might suppose. Your brain interprets it as being actually burned. As Joshua Tewksbury of the University of Colorado has put it, “Chilies innervate the same neurons that you activate when you touch a 335-degree burner. Essentially, our brain is telling us that we have got our tongue on the stove.” In the same way, menthol is perceived as being cool even in the heated smoke of a cigarette.
The active ingredient in all chili peppers is a chemical called capsaicin. When you ingest capsaicin, the body releases endorphins—it’s not at all clear why—and that provides us with a literally warm glow of pleasure. As with any warmth, however, it can quickly grow uncomfortable and then intolerable.
The amount of heat in chilies is measured in units called Scovilles, after Wilbur Scoville (1865–1942), an unassuming American pharmacist who had no known interest in hot dishes and very possibly never tasted a genuinely spicy food in his life. Scoville spent much of his career training students at the Massachusetts College of Pharmacy and churning out academic papers with titles like “Some Observations on Glycerin Suppositories,” but in 1907 at the age of forty-two, apparently tempted by a big salary, he moved to Detroit to take up a job with a large pharmaceutical company, Parke, Davis & Co. One of his tasks there was to oversee production of a popular muscle salve called Heet. The warmth of Heet came from chili peppers—the same ones used in food—but the heat of peppers varied enormously from one delivery to another, and there was no reliable way of judging how much to put into any given batch. So Scoville came up with something called the Scoville Organoleptic Test, which was a scientific method for measuring the hotness of any pepper. It is still the standard used today.
A bell pepper will have a Scoville rating of between 50 and 100. Jalapeños usually measure in the range of 2,500 to 5,000 Scovilles. Nowadays many people breed peppers specifically to make them as hot as possible. The record holder at the time of writing is the Carolina Reaper at 2.2 million Scovilles. Capsaicin in pure form has 16 million Scovilles. A purified version of a Moroccan spurge plant—a cousin of the innocuous common garden flowering euphorbia—has been measured at 16 billion Scovilles. Such superhot peppers are of no use in foods—they are beyond any human threshold—but they are of interest to manufacturers of pepper sprays, which also use capsaicin.
Capsaicin has been reported to lower blood pressure, fight inflammation, and reduce susceptibility to cancer, among quite a lot else of benefit to the average human. In a study reported in the British Medical Journal, Chinese adults who ate a lot of capsaicin were 14 percent less likely to die, from any cause, during the period of the study compared with less adventurous eaters. But, as always with these findings, the fact that the subjects ate a lot of spicy food and were 14 percent better at surviving may only be coincidental.*2
Incidentally, we have pain detectors not only in the mouth but also in the eyes, anus, and vagina, which is why spicy foods can cause discomfort there.
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As far as taste goes, our tongue can only identify the familiar basics of sweet, salty, sour, bitter, and umami (a Japanese word meaning “savory” or “meaty”). Some authorities believe we also have taste receptors specifically allocated for metal, water, fat, and another Japanese concept called kokumi, meaning “full-bodied” or “hearty,” but the only ones that are universally accepted are the five basics.
In the West, umami is still a rather exotic concept. It is actually a comparatively recent term even in Japan, though the taste has been known for centuries. It comes from a popular fish stock called dashi, which is made from seaweed and dried fish scales, and when added to other foods makes them even more delicious and imparts an ineffable but distinctive flavor. In the early twentieth century, a Tokyo chemist named Kikunae Ikeda determined to identify the source of the flavor and to try to synthesize it. In 1909, he published a brief paper in a Tokyo journal, identifying the source of the flavor as the chemical glutamate, an amino acid. He dubbed the flavor umami, meaning “essence of deliciousness.”
Ikeda’s discovery attracted virtually no attention outside Japan. The word “umami” isn’t recorded anywhere in English until 1963, when it appeared in an academic paper. Its first appearance in a more mainstream publication was in 1979 in New Scientist. Ikeda’s article wasn’t translated into English until 2002, after umami taste receptors had been confirmed by Western researchers. But in Japan, Ikeda became celebrated, not as a scientist so much, but rather as a co-founder of a great company, Ajinomoto, created to exploit his patent for making synthetic umami, in the form universally known today as monosodium glutamate, or MSG. Today Ajinomoto is a behemoth, making about one-third of all the world’s MSG.
MSG has had a hard time of it in the West since 1968 when The New England Journal of Medicine published a letter—not an article or a study, but simply a letter—from a doctor noting that he sometimes felt vaguely unwell after eating in Chinese restaurants and wondered if it was the MSG added to the food that was responsible. The headline on the letter was “Chinese-Restaurant Syndrome,” and from this small beginning it became fixed in many people’s minds that MSG was a kind of toxin. In fact, it isn’t. It appears naturally in lots of foods, like tomatoes, and has never been found to have deleterious effects on anybody when eaten in normal quantities. According to Ole G. Mouritsen and Klavs Styrbaek in their fascinating study, Umami: Unlocking the Secrets of the Fifth Taste, “MSG is the food additive that has been subjected to the most thorough scrutiny of all time,” and no scientist has ever found any reason to condemn it, yet its reputation in the West as a source of headaches and low-grade malaise now appears to be undimmed and permanent.