Background: Natural products are commonly used for treating health problems. These
products may be associated with adverse events, which are defined as "noxious and unintended
response to a medicinal product" by the European Medicine Agency.
Objectives: To identify studies describing at least one adverse event (or with potential to promote
an adverse event) related to the use of natural products, as well as to describe the involved
product(s) and adverse event(s).
Methods: A pre-systematic review following the Preferred Reporting Items for Systematic
Reviews and Meta-Analyses criteria. Keywords: "natural product(s)" and ["adverse drug
reaction(s)" or "adverse effect(s)"]. Screened databases: PubMed, SciELO, DOAJ and Google
Scholar. Inclusion criteria: Papers describing at least one adverse event associated with the use of
natural products and published between 2017 and 2019. Exclusion criteria: Repeated studies,
reviews and papers written in other languages than English, Portuguese, French or Spanish.
Results: 104 studies were identified (20 PubMed; 0 SciELO; 2 DOAJ; 82 Google Scholar), but
only 10 were selected (4 PubMed and 6 Google Scholar): 1 in-vitro study; 2 non-clinical studies, 1
study reporting in-vitro and clinical data and 5 case reports. Globally, 997 reports of adverse drug
reactions with natural products were identified, mainly non-severe cases.
Conclusion: Since a limited number of studies was found, we conclude that adverse events due to
natural products may be underreported or natural products may have a good safety profile. This
review contributes to assuring the safety of natural products consumers by evaluating the
knowledge/information on the potential adverse events and interactions of these products.