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02
Reason Why You Miss
Mint in Summer

Now we understand the first secret of TRP channels as temperature sensors, which have warned us about the dangers facing us in nature since the primitive ages. The TRP channels detect not only temperature but also acids, alkalis, plant-derived compounds and many others. The second secret is TRPM8 which detects one plant-derived compound.
illustration: Yutanpo Shirane

You feel cool and refreshed because mint activates TRPM8

In summer, people pay attention to mint because it contains menthol which gives a cool and refreshing sensation. It is attributable to one of the TRP channels, or TRPM8, that is activated by menthol. TRPM8 detects a temperature of about 26℃ or less and also menthol at a higher temperature, for example 30℃, thereby tricking the brain into feeling "cool."

The combination of ice cream and mint produces synergy between them, providing us with a cooler sensation. In hot countries, people often drink cold cocktails containing mint leaves. One of them is a mojito with a lot of mint, which was born in Cuba. Author Earnest Hemingway routinely presented it as his favorite drink. Its origin is "El Draque," a cocktail containing vitamin-rich lime as disinfectant as well as mint. It was invented when cholera was widespread in Cuba. It had medicinal effects. If he had written a story of a little Caribbean mermaid swimming gracefully in a mojito with a lot of mint, it would have been like a breath of cool and fresh air..

Menthol and eucalyptus, the perfect combination to produce a cool and refreshing sensation

Like menthol, eucalyptol, or a compound of eucalyptus leaves, is known to activate TRPM8 and produces a cool sensation. In addition, eucalyptol is an ideal partner for menthol.

A high-level of menthol can be too strong and induce an unpleasant sensory irritation. It is caused when the high-level of menthol activates not only TRPM8 but also TRPA1. Eucalyptol has been proved to control activation of TRPA1. Therefore, combining eucalyptol and menthol can control such unpleasant irritation while maintaining a strong sensation of coolness and being refreshed. This surprising combination was discovered by Mandom research.

illustration: Yutanpo Shirane

Koalas eat eucalyptus leaves and spend their days in eucalyptus trees. They are active predominantly at night and sleep or rest nearly 20 hours a day in trees, because it is cooler in the trees than below them. They defend themselves against the heat by climbing a tree. Eucalyptus leaves are poisonous and are eaten only by koalas. Since the old times, the leaves have been used to treat fevers by the indigenous Australians and are called "antipyretic trees" in France. Both eucalyptus and mint have been known to have analgesic/sedative and anti-inflammation effects, and now, their mechanisms are being explained by the TRP channels.

Does hugging a koala living on eucalyptus leaves activate TRPM8 and make us feel cool? No, it does not. Before asking it, it is not good to hug koalas in Japan. They are highly sensitive to human handling. Be satisfied with looking at the lovely koalas, which heal us.

Independent research: Feel the TRP channels (2)

How does water feel when you take a
mint tablet before drinking water?

Answer: Synergy between "mint and cold water" makes water feel colder. 

The reason why you find water colder with a mint tablet is because menthol contained in the mint tablet activates TRPM8 and causes synergy with cold water to makes it feel colder. Try a mint tablet and a cup of water to feel cooler in hot summer.

Why do you feel cool?