Since publication in 1999 of the first revision of Herbs of Choice, a plethora of publications has extended both the range and depth of herbal medicinal science. Notable has been the introduction to the West of a number of herbs long popular in Eastern traditional medicine systems. Prominent among these have been Andrographis paniculata, Petasites hybridus (butterbur), Centella asiatica (gotu kola), Bacopa monnieri, and Citrus aurantium (bitter orange) as an ephedra substitute.
There has also been an explosion of concern and scientific investigation into the potential for herb–drug interaction influencing clinical outcomes— from grapefruit (Citrus x paradisi) to St. John’s wort (Hypericum perforatum). Examination of bleeding and coagulation associated with herbs has been expanded. Recent research has also clarified certain aspects of the mechanisms of action of a number of popular herbs, such as feverfew, ginkgo, and ginseng. Particularly, a wholesale revision of the feverfew treatment has been effected. Phytochemical treatment of liver disease and the activity of phytoestrogens have been more widely explored.
The expansion of herbal research in the United States, heralded in the second edition of Herbs of Choice, has markedly increased. Since the 1997 publication of a fair and fairly positive assessment of Ginkgo biloba extract for treatment of Alzheimer’s disease and vascular dementia in the
Journal of the American Medical Association (JAMA), a number of articles have appeared in medical journals, some blatantly deficient in appreciation of herbal scientific parameters. Conspicuous among the latter have been two JAMA reports regarding the effectiveness of St. John’s wort (SJW) in major depression, without acknowledging that SJW is recognized for its effectiveness in treating mild to moderate depression. The results of a later study were widely publicized as demonstrating the ineffectiveness of SJW, without noting that the widely prescribed pharmaceutical sertraline was also not significantly different in effect from placebo. Most herbal scientists attribute the failure of both test treatments to relatively long-term, chronic serious depression. The effectiveness of echinacea in treatment of the common cold has also come under scrutiny by the medical community:Knight’s critique focused on two studies that generated negative findings but addressed prevention rather than symptomatic treatment of rhinoviral inoculation. A recent article in the New England Journal of Medicine (NEJM) found no evidence of any clinically significant efficacy of three extracts of Echinacea angustifolia root. The results of that study prompted Samson to criticize the
National Center for Complementary and Alternative Medicine for funding investigation of “implausible remedies” and charge a prevalent tendency of herbal enthusiasts to “dismissing disproof.” Two other recent NEJM publications report ineffectiveness of three popular herbal remedies: saw palmetto for benign prostatic hyperplasia, glucosamine-chondroitin for painful knee osteroarthritis, and black cohosh for hot flashes.
The herbal scientific literature is plagued by mixed results from different studies with a number of medicinal plants. These mixed results are widely believed to be due to methodological inadequacies or variation in the chemical character of test treatments.
A recent publication lamented the lack of adequate characterization of herbal supplements subjected to randomized controlled trials (a position long embraced by the late Professor Tyler9) and stressed the importance of quality control issues in ensuring “the value of otherwise well-designed clinical trials.”10 Yet another publication assessed five popular botanical dietary supplements from nine manufacturers; echinacea, ginseng, kava, SJW, and saw palmetto were analyzed for compliance of marker compound content with label claims. 11 Although little variability was noted between different lots of the same brand, content of marker compound varied widely between brands, as did information regarding serving recommendations and herbal parameters such as species, part of plant, and marker compounds targeted.
All these considerations recommend much closer attention to all phases of the manufacture of botanical test preparations and committed response to the near-mantra call for larger, better-designed clinical trials of longer duration, with properly characterized treatments.
I am considerably indebted to Kenneth Jones, Armana Research, BC, for contributions to my scientific information base and for thoughtful and critical discussions of a wide range of herbal medicinal issues. The American Botanical Council’s HerbClip™ service has also been a valuable source of current publications.
Dennis V. C. Awang
White Rock, BC, Canada