The umeboshi, salt pickled plum, is one of Japan's most remarkable traditional foods, revered since ancient times both as an everyday food and a potent health tonic.

Its taste has been described as the culinary equivalent of a cold shower. Food writer Robbie Swinnerton says, "the abrupt, searingly tart, tangy, salty taste jolts the eyes open, shakes the stomach awake, sandpapers off any staleness from the taste buds, and gets the day off to an unforgettable start."

Besides its dramatic flavour, the Japanese pickled plum has remarkable properties. Its powerful acidity has a paradoxical alkalinising effect on the body, neutralising fatigue, stimulating digestion, and promoting the elimination of toxins. In Japan, a piece of umeboshi each day is regarded as one of the best tonics available.

The oldest Japanese record of pickled plums is in a medical text written about one thousand years ago. Umeboshi were used to prevent fatigue, purify water, rid the body of toxins, and cure specific diseases such as dysentery, typhoid, and food poisoning. Slowly, extensive folklore developed about umeboshi's ability to prevent and cure certain diseases.

During the samurai era, the pickled plum was the soldier's most important field ration. It was used to flavour foods such as rice and vegetables, and its high acidity made it an excellent water and food purifier, as well as an effective antidote for battle fatigue.