Scientists have cast doubts on the efficacy of Chinese herbal medicines in preventing type 2 diabetes in high-risk patients.
In China, Korea and Japan herbal pills, teas and powders have been used for a long time to treat pre-diabetes and diabetes.
But the researchers say that there is lack of hard scientific evidence to confidently recommend their use.
"People with impaired glucose tolerance are more likely to develop full blown diabetes and it may be possible to prevent or delay the onset of the disease through lifestyle changes and medication," said lead researcher, Suzanne Grant of the Centre for Complementary Medicine Research at the University of Western Sydney in Australia.
"Chinese herbal medicines have been used for this purpose for a long time, so there is plenty of anecdotal evidence for their safety and effectiveness, but we were interested to find out whether scientific research could provide a basis for recommending these alternative treatments," she added.
During the study, Cochrane research team analysed 16 clinical trials including 1,391 people who received 15 different herbal formulations.
According to their findings, combining herbal medicines with lifestyle changes is twice as effective as lifestyle changes alone at normalising patients' blood sugar levels.
Those given the herbal formulations were less likely to develop full blown diabetes during the study period. Trials included in the review lasted from one month to two years. No adverse effects were reported in any of the trials.
"Our results suggest that some Chinese herbal medicines can help to prevent diabetes, but we really need more research before we can confidently say that these treatments work," said Grant.
"The real value of the study is as guidance for further trials. We need to see more trials that make comparisons with placebos and other types of drugs, and better reporting on the outcomes of these trials," she added.