Eighty five studies were included in the review. The majority of studies were conducted in China (77 studies); others were in India (two studies), Russia (four studies) and the Ukraine (two studies).
Studies evaluated herbal preparations (three studies); finished manufactured herbal products (51 studies); the use of a combination of vitamins and other herbal supplements (27 studies); and pharmaceutical preparations (four studies).
Only five trials were reported to be randomised. All five randomised trials had sample sizes that were too small to detect an effect on the incidence of liver damage and had a follow-up of two months or less. Three of these trials also did not report any method of allocation concealment.