T HE WORLD loves a cuppa. Even though it takes just a few grams for a brew-up, some 3m tonnes of tea are consumed every year. And tea can be good for you, as it contains compounds that help to lower cholesterol and reduce the risk of cardiovascular disease. But there is a downside. Tea contains caffeine which, although it improves mental alertness, can also cause anxiety, insomnia and other problems.

Sipping decaffeinated tea can help, but there are drawbacks to this, too. Stripping away caffeine from tea involves either immersing the leaves in carbon dioxide at extremely high pressure or treating the leaves with searing hot water. Although this will get rid of most of the caffeine, it can cause collateral damage to some of the fragile compounds that give tea its benefits. And, as with decaf coffee, which is treated in similar ways, many people argue that it also spoils the flavour.

What would be agreeable is a tea plant that provides all the taste and goodness but with little or none of the caffeine. Liang Chen and Ji-Qiang Jin of the Tea Research Institute of the Chinese Academy of Agricultural Sciences think they have found just such a plant growing wild in a remote area in Fujian province, southern China. As they report in the Journal of Agricultural and Food Chemistry, not only is the tea plant naturally caffeine-free but it also contains a number of unique medicinal compounds that, the locals believe, offer considerable health benefits.

This is not the first such find. In 2011 a tea plant discovered in neighbouring Guangdong province was found to contain little or no caffeine. That plant, known as Camellia ptilophylla, contains compounds that look promising for the treatment of obesity, although research is still continuing. That discovery spurred Chinese botanists to look for others that might be hiding in the rugged vastness of the country, and the latest find is one result.

Known locally as Hongyacha, the newly discovered plant grows only between 700 and 1,000 metres above sea level around a handful of Chinese alpine villages. Although Hongyacha has never been formally studied in a laboratory, people in the region have been experimenting with its properties for generations and claim it provides medical benefits ranging from curing colds and lowering fevers to soothing stomach pains.

Dr Chen and his colleagues confirmed that Hongyacha does indeed lack caffeine. Using a variety of procedures, including liquid chromatography and mass spectrometry, they found it also contains an intriguing array of other compounds in its buds and leaves. Of particular interest was a compound in the plant’s leaves that is known to hamper the growth of tumours as they attempt to improve their access to nutrients by growing new blood vessels.

Upon closer inspection of Hongyacha’s genetics, the researchers discovered that the absence of caffeine was the result of a mutation in the gene that codes for the production of an enzyme known as caffeine synthase. Somewhat surprisingly, this mutation is different from the one found in C. ptilophylla and suggests that the two plants made their evolutionary journey towards losing caffeine independently.

Precisely why caffeine—which, being lethal to many insects, functions as a pesticide in some plants—was selected against by evolution remains an open question. It is possible that the metabolic cost of producing caffeine was high and that other compounds that were easier for the plant to make were as effective. It is also possible that threats from insects were reduced at some point in the history of these two plants, and that led to the selection of individuals that lacked the insecticide.

The researchers are now exploring methods to protect Hongyacha in its natural habitat while further studies are carried out. It can take time—and sometimes it does not work—for new plant varieties to be bred for commercial use. A pair of naturally caffeine-free coffee plants were discovered in 2003, but little progress has been reported. Tea enthusiasts will be watching Hongyacha with interest. And others will wonder what else is out there.