Unlocking the Science of Wasabi

Wasabi typically comes as a gob of green paste with a plate of sushi or sashimi.

hide captionWasabi typically comes as a gob of green paste with a plate of sushi or sashimi.

Rick Gayle Studio/CORBIS

Scientists have figured out why eating a dollop of wasabi makes it feel like your head might explode — a particular class of receptor molecules on the surface of nerve cells. The discovery could lead to a new class of painkillers for a variety of conditions.

Wasabi is that sinus-stinging green paste that's served with sushi and sashimi. Lately, real wasabi — Eutrema japonica, a root-like rhizome — has become rare. Some restaurants use a mixture of horseradish and green food coloring, with little or no actual wasabi in the mix. But as it turns out, the kick is the same.

Some food scientists believe people eat hot foods to show off, or because they get an endorphin rush from the pain — or they like the pain itself. Precisely why is still a matter for further inquiry.

Telling the Brain 'Ouch!'

There are molecules that sit on the outside of human cells called receptors. The receptor's job is to "sniff" molecules in the vicinity of the cell, and if it finds something it recognizes, the receptor triggers changes inside the cell — it could be to prompt the cell to make a hormone, for example, or increase the production of a particular protein.

There's a receptor on the outside of some nerve cells called TRPA1. When TRPA1 sniffs something it recognizes, it causes the nerve cell to send a signal to the brain.

One of the molecules TRPA1 recognizes is a class of chemicals called isothyocyanates — and it just so happens that foods like wasabi and mustard oil are packed with isothyocyanates. So when wasabi comes in contact with a nerve cell outfitted with a TRPA1 receptor, the nerve cell tells the brain, in essence: "Ouch."

In an evolutionary sense, the reason plants started making these compounds was to try to stop humans or other omnivores from eating them. It didn't work.

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