The clinical efficacy and safety of Tulsi in humans: A systematic review of the literature 

This 2017 review was the first systemic review of human clinical trials relating to clinical effects of ingested holy basil (common name tulsi). The review found 24 articles that met their inclusion criteria with the most outcome measures relating to blood glucose levels, lipid profile, blood pressure, immune response, neurocognitive changes, fatigue and mood. Regarding safety and adverse events, only one of the 24 studies reported occasional nausea in supplementation with obese patients. 

References:

Jamshidi N, Cohen MM. The Clinical Efficacy and Safety of Tulsi in Humans: A Systematic Review of the Literature. Evid Based Complement Alternat Med. 2017;2017:9217567. doi:10.1155/2017/9217567