Adverse effects of herbal preparations of Pistacia species: a systematic review and meta-analysis of randomised controlled clinical trials

Introduction

Pistacia species (spp.) have nutritional and therapeutic usage. This systematic review and meta-analysis aimed to assess the safety of herbal preparations of Pistacia spp. in the randomised controlled clinical trials.

Methods

Relevant keywords were searched in PubMed, Embase, Scopus, Web of Science, and Google Scholar up to August 2023. The quality and risk of bias were assessed using the Cochrane Collaboration tool. Pooled effect sizes for adverse events and withdrawal rates were reported as relative risks (RR) and 95% confidence intervals (CI) using RevMan software. Forest plots were generated to visualise effect sizes for each comparison.

Results

Twenty-six eligible randomised controlled clinical trials (RCTs) were included in the pooled analysis (1 851 subjects). Finally, 14 and 13 adverse events were reported for the intervention and comparator groups, respectively, without any significant difference (RR: 0.99 [95% CI: 0.48, 2.05]; Z: 0.01, P: 0.99). Most adverse events in the experimental groups were mild gastrointestinal events. The intervention groups reported lower withdrawal rate than the comparator groups. However, the difference was not significant (RR: 0.81 [95% CI: 0.62, 1.05]; Z: 1.61, P: 0.11). These findings were consistent across Pistacia spp. and treatment indication subgroups.

Conclusion

The safety of Pistacia spp. was comparable to that of placebo, regular diet, or conventional treatments, with few adverse events and no serious adverse events. However, given the high risk of bias, such as small sample sizes, future high-quality, large-scale RCTs with diverse demographics are necessary to confirm the safety and efficacy of these preparations especially for specific populations or long-term usage.