Herbal medicines for the treatment of functional and inflammatory bowel disorders.

In many parts of the world, there continues to be a long-standing tradition of prescribing herbal products for a range of gastrointestinal conditions. Scientific evidence supporting the use of all herbal preparations is imperfect, however, and available studies are plagued by methodological limitations. For functional gastrointestinal disorders, there is limited evidence supporting the use of some well-characterized preparations. A number of herbals have immunomodulatory activity, and in inflammatory bowel disease there are limited positive placebo-controlled trials; other studies used active controls with suboptimal doses of the comparators. Like all drugs, herbals can lead to serious adverse events (eg, hepatic failure). Quality control is a serious issue to consider when prescribing herbal medicines. Many herbal preparations are marketed without evidence for stringent adherence to good manufacturing practice guidelines. Unpredictable environmental conditions may affect the composition and the concentration of the active ingredients of plant extracts. Further, commercial herbal products usually combine a variable plethora of chemical families with possible medicinal utility. While some of these ingredients might be of benefit, the concentration and dose of these constituents needs to be closely monitored. Physicians and regulators need to remain very cautious about the use of herbal remedies. Appropriate scientific evidence for the claimed clinical benefits should become mandatory worldwide, and the standards for production and safety monitoring should comply with established standards for chemically defined products. If these principles were adopted, the full value of herbal remedies may come to light, particularly as the individually bioactive compounds present in these preparations become recognized.