The efficacy of individual herbs and supplements to help glucose control in diabetics is still unproven, suggest researchers compiling a review of all published studies.
However, most herbals and vitamins used by diabetes patients appear to be generally safe, said the researchers from the Harvard Medical School and Beth Israel Deaconess Medical Center in Boston, Massachusetts. Coccinia indica and American ginseng appear to have the most evidence supporting their potential benefits.
The team searched online databases, including MEDLINE, OLDMEDLINE, the Cochrane Library Database, and HealthSTAR, from the beginning of the databases to May 2002. They also performed hand searches and consulted with experts in the field.
A total of 108 trials examining 36 herbs (single or in combination) and nine vitamin/mineral supplements, were analysed. There were 58 controlled clinical trials involving individuals with diabetes or impaired glucose tolerance (42 randomised and 16 non-randomised trials). Most studies involved patients with type 2 diabetes. Heterogeneity and the small number of studies per supplement precluded formal meta-analyses, write the researchers in this month's Diabetes Care.
Of these 58 trials, the direction of the evidence for improved glucose control was positive in 76 per cent of trials (44 of 58). Very few adverse effects were reported.
Several supplements may warrant further study, concluded the scientists. The best evidence for efficacy from adequately designed randomised controlled trials (RCTs) is available for Coccinia indica and American ginseng, according to the study, although chromium has been the most widely studied supplement.
Other supplements with positive preliminary results include Gymnema sylvestre, Aloe vera, vanadium, Momordica charantia, and nopal.