Researchers say the benefits may be attributed to capsaicin and allyl isothiocyanates, phytochemicals that give the mustard its characteristic flavor.

The key is allyl isothiocyanate, the compound in wasabi that gives out its distinctive smell and can be detected even during sleep.

This oil is a compound of sulphur, carbon, and hydrogen, and is called sulphide of allyl, because of its origin in the allium tribe.