Adverse Effects of Plant Food Supplements and Botanical Preparations: A Systematic Review with Critical Evaluation of Causality

Aims: The object of this review was to collect available data on 1) adverse effects observed in humans from the intake of plant food supplements (PFS) or botanical preparations; 2) the misidentification of poisonous plants; 3) interactions between PFS/botanicals and conventional drugs or nutrients. Methods: PubMed/MEDLINE and Embase were searched from database inception to June 2014, using the terms “adverse effect/s”, “poisoning/s”, “plant food supplement/s”, “misidentification/s”, and “interaction/s” in combination with the relevant plant name. All papers were critically evaluated according to the WHO Guidelines for causality assessment. Results: Data were obtained for 66 plants that are common ingredients of PFS; of the 488 papers selected, 398 (81.6%) dealt with adverse effects directly associated with the botanical and 89 (18.2%) concerned interactions with conventional drugs. Only 1 case was associated with misidentification. Adverse effects were reported for 39 out of the 66 botanical substances searched. Of the total references, 86.5% were associated with 14 plants, including Glycine max/soybean (19.3%), Glycyrrhiza glabra/liquorice (12.5%), Ginkgo biloba/ginkgo and Camellia sinensis/green tea (both 8.6%). Conclusions: Considering the length of time examined and the number of plants included in the review, it is remarkable that: 1) the adverse effects due to botanical ingredients were relatively infrequent, if assessed for causality; 2) the number of severe clinical reactions was very limited, but some fatal cases have been described. Data presented in this review were assessed for quality in order to make the results maximally useful for clinicians in identifying or excluding deleterious effects of botanicals