This 2011 double blind placebo-controlled trial tested the effects of a 300 mg 70% ethanolic tulsi extract on healthy volunteers between the ages of 18-60 yo compared with placebo (n=24). Whole blood cultures and cytokine assay was performed at baseline, at 4 weeks of placebo, after 3-week washout period, and after completion of crossover intervention. Two patients were unable to complete the study due to adverse effects of nausea and loose stools at the first visit. While this study found statistically significant increases in both IFN-gamma and IL-4 in the treatment group vs placebo arm, the IFN- gamma increase was still higher and accompanied a significant difference in the lymphocytes and NK-cells after 4 weeks of supplementation.
Mondal S, Varma S, Bamola VD, Naik SN, Mirdha BR, Padhi MM, Mehta N, Mahapatra SC. Double-blinded randomized controlled trial for immunomodulatory effects of Tulsi (Ocimum sanctum Linn.) leaf extract on healthy volunteers. J Ethnopharmacol. 2011 Jul 14;136(3):452-6. doi: 10.1016/j.jep.2011.05.012. Epub 2011 May 17. PMID: 21619917.