According to a recent study by Taiwanese experts , people buying the popular herbal medicine may be actually getting virtually none.
St John's Wort, or Hypericum, can have mild antidepressant effects, although doctors warn it can interfere with the effects of other medicines. None of the tablets tested had as much of the active ingredient as claimed, said the researchers.
Two chemicals are thought to be responsible for the psychoactive effects of St John's Wort. These are hypericin - the chemical ingredient normally named on the label - and a related chemical called pseudohypericin. However, it was seen to contain more pseudohypericin than hypericin itself. The levels of hypericin fell far short of those mentioned on the label. One type of tablet contained only 1.7% of the claimed dose - the best brand managed only 38.5%. Even when the hypericin and pseudohypericin contents were added together, all but one still came up short of the totals on the packaging.
Doctors say, that even if they were consulted by patients about possible interactions between their conventional medicines and St John's Wort, it would be impossible for them to know exactly how much hypericin their patient was actually taking. They also say that, "Inaccurate labelling has at least one of two effects - the first is potentially to lead to incorrect dose when the label information is complied with. "The second is to degrade the perceived significance of the label information among either dispensing practioners, or the patients.
Researchers say they hope that these findings will add pressure on manufacturers to introduce firmer regulation on the manufacture of herbal medicines - which do not have to be made to the same rigid standards as pharmaceutical products.