Picture of calcium oxalate crystals, changing shape with different amounts of green tea. The flatter crystals form less stable kidney stones that break up easily.

(PhysOrg.com) -- Drinking green tea can help prevent the formation of large kidney stones, report Chinese scientists in the Royal Society of Chemistry journal CrystEngComm.

The researchers have found that compounds in the tea make it difficult for larger stones to form, by changing the shape of mineral crystals that might otherwise clump together.

The smaller stones that are left are painlessly passed out in urine.

Kidney stones affect up to five per cent of the world population, and the prevalence is rising, says Xudong Li at Sichuan University, Chengdu, China, lead author of the article.

Compounds in the tea called phenols bond to the calcium oxalate, making the resulting crystals a different shape and less likely to clump together to form large .

More information: Original article: www.rsc.org/Publishing/Journal … cle.asp?doi=b913589h

Provided by Royal Society of Chemistry