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Miracle berry: The flavor-changing fruit that reveals the illusory nature of our senses

Bite into a miracle berry and you'll perceive intense sweetness — but only after you eat something acidic, too.
miracle berry
Miracle berry. (Credit: weerapat1003 / Adobe Stock)
Key Takeaways
  • In The Man Who Tasted Words, author and neurologist Guy Leschziner explores the often hazy relationships between reality and our senses.
  • This book excerpt overviews a peculiar case of parosmia, which describes abnormalities in one's sense of smell.
  • Some people's senses undergo drastic changes that leave them perceiving the world in significantly different ways — and not always for the better.

Excerpted from THE MAN WHO TASTED WORDS by Guy Leschziner. Copyright © 2022 by Guy Leschziner. Reprinted by permission of St Martin’s Publishing Group.

Few examples demonstrate the illusory nature of our chemical senses better than Synsepalum dulcificum, otherwise known as the miracle-berry plant. Native to West Africa, this shrub grows a few meters high and produces 2cm red fruit shaped a little like olives or acorns – so far, it may sound rather unassuming and not very miraculous. But the miracle happens when you chew the flesh of the berry. On its own, it is tangy and very mildly sweet, but nothing much to write home about. But after you’ve eaten the berry, if you then bite a lemon or a lime, even drink some vinegar, your mouth will be flooded with sweetness, an explosion of the intense taste of sugar. The sweet taste will linger for several minutes, until the active compound of the berry, a substance known as miraculin, is washed away by your saliva. On its own, miraculin does nothing. In the normal setting of the mouth, with neutral saliva, the miraculin binds to sweet receptors and simply blocks them, not really stimulating a sensation of sweet. But when the mouth becomes acid, when saliva mixes with something sour, the miraculin binds with salivary proteins and changes its structure, suddenly making it able to trigger these sweet receptors rather than blocking them. A rather remarkable illusion of taste, it is a potent illustration of the loose nature of the relationship between the physical world and our experience of it.

“I would have people make jokes of it, just laugh at me, basically. I’d be sitting there with a handkerchief over my nose, trying to stop any smells, trying to stop breathing, really. I’d breathe through my mouth instead of my nose to stop having to smell that smell, and people would just make fun of me. I even had somebody say, “Well, at least you’re not deaf or blind.”’ The bitterness is evident in Joanne’s voice as she tells me of her experiences of the past five years – bitterness at the lack of recognition of the impact of her condition, bitterness at the all-pervading effects of it. 

Joanne’s problems started innocuously enough. A simple head-cold, in her mid-forties, back in 2015; the kind of cold that is familiar to anyone in the UK, an intermittent companion of autumn, winter and, for that matter, spring. Joanne, based in the far north-east, in Tyneside where the biting wind whips in off the North Sea, would also without doubt have been no stranger to a cold. But this one lingered for weeks, causing some chronic sinus issues, and ultimately Joanne needed a course of antibiotics to shift it. Her cold settled and she thought nothing more of it – until a few weeks later, when she noticed something strange. “I started to notice a really bad, distorted smell. I couldn’t put my finger on it. It could be between rotting flesh or sewage. Really a foul, putrid smell.” As time went on, Joanne found that this stench became all-pervasive, all-consuming. “It just got worse and worse. It was every second of the day. “But it was not only her sense of smell that was affected. The reek of decay permeated her food as well. “Everything tasted either like a chemical taste or as if it had gone off, as if it were moldy or rotten.”

Specific smells seemed to heighten the unpleasantness, and the range of triggers was not at all conducive to normal life. “If I came in contact with cigarette smoke, cooked food, coffee, even fabric softener or perfumes, that putrid smell was just heightened twenty-fold.” The smell of mint in toothpaste induced gagging, leading her to seek out flavorless toothpaste. Going into work, surrounded by the perfumes and aftershaves of her colleagues, became intolerable. She went off sick for several months. Even family life became fraught. A Sunday lunch with her partner and her sister’s family would become a trial. The smell of food, the smoke of the coal fire, people’s personal scents, all became quickly overwhelming. “So I just escaped outside. But you’re surrounded by smells outside as well. Just by going to the shops, you’ll pass people smoking a cigarette. I would run a mile in the opposite direction. Even the smell of cut grass – I couldn’t stand it.”

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All this quickly took its toll. Joanne found her new reality extremely distressing. “I just wanted to sleep all the time, because that was my only escape. I wanted to hibernate. I didn’t want to go out, socialize, go to work. I literally just wanted to sleep.”

Like the miracle berry, Joanne’s sensory world had become illusory. The perpetual odor of death, putrefaction, decay – an illusion of smell, horrific rather than miraculous. Joanne’s distress was compounded by a lack of help or understanding. Her first visit to her general practitioner was met with a blank look. “My GP hadn’t heard of it at all,” Joanne recalls. She was given various nasal sprays and medications, to no avail. I ask Joanne if her family thought perhaps that the problem may be psychological – I have previously come across patients so depressed as to become psychotic, and to have delusions of the world around them rotting or dying. “I think they understood it was biological, but they just didn’t know how to help.” As is so frequently the case, “Dr Google” gave an answer of sorts. It gave her condition a name. “I had never heard of it, and when I challenged my GP, they hadn’t heard of it either.” That name is parosmia.


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