Kombucha has become the new drink craze, beloved by Halle Berry amongst others. Picture: Peter Kramer

London - Its nickname sounds off-putting enough: “mushroom juice”.

But when you find out this fizzy, sour tea is made of fermented bacteria and yeast, and tastes like a noxious vinegar, you’ll probably be running for the hills rather than to your nearest stockist.

Despite all that, kombucha has become the new drink craze, beloved by Gwyneth Paltrow, Reese Witherspoon, Halle Berry and Madonna, who claim it boosts their mood and concentration and wards off hunger pangs.

It originates from China, where many describe it as the “elixir of life” because of the natural probiotics and antioxidants it contains. Bacteria and yeast are combined with tea, and usually sugar, to produce what looks like a rapidly expanding brown mushroom before it is separated, bottled and sold in organic and health-food stores.

The best that can be said of it is that it tastes a tiny bit like beer or a very acrid apple cider. Others have opted for “cough medicine”.

Nutritionist Rick Hay says: “Kombucha is made by adding the bacterial colony to sugar and tea – the mix is then fermented.”

Fans say it benefits the immune and digestive systems and boosts energy.