The harmful potential of herbal and other plant products

Herbs, herbal products, food additives and other dietary supplements derived from plants are widely consumed in many countries. The literature on intoxications from such behaviour is increasing. This article reviews some of the factors predisposing to intoxication from the use of herbs, with examples drawn largely from pyrrolizidine alkaloid-containing plants. Poisonings occur because of the misidentification of a plant, or the unknown or ignored toxicity of a correctly identified plant. Factors contributing to problems include the difficulties of identifying chopped, processed herbs or plant mixtures, persistent use of a toxic plant, variability in the toxic constituents of a plant, problems of nomenclature, adulteration and the difficulty in establishing the chronic toxic potential of a plant. Certain users of herbs are at high risk of intoxication. These include chronic users, those consuming large amounts or a great variety, the very young, fetuses, the elderly, the sick, the malnourished or undernourished and those on long term medication. Members of certain cultural groups in North America are also at higher risk. Certain plant toxins may be gender-selective in their action. To encourage discussion, some approaches to regulation are suggested, and some commonsense guidelines are given.