Table 1.

Characteristics of the studies included.

Reference.	Type of Studies	Sample Size		Age (Mean)	Male (%)	Intervention *	Conclusion	Quality Assessment
		Intervention	Control
Ahmadi, Iran, 2020 [34]	Randomized triple-blind placebo-controlled clinical trial [IRCT20200408046990N1] Treatment duration: 2 weeks Follow-up: 2 weeks after treatment	30 mild to moderate COVID-19 patients	27 mild to moderate COVID-19 patients	43.15 ± 11.58	58.3%	Sinacurcumin® soft gel 40 mg -Intervention group received 2 soft gels after breakfast and 2 soft gels after dinner daily for 2 weeks. -Placebo soft gels were prepared by the same company, with the same appearance containing all ingredients of medicine soft gel except curcumin with same dosing (2 soft gels twice daily after meal)	Positive effect of curcumin therapy. All symptoms except sore throat resolved faster in the treatment group, and the difference was significant for chills, cough, and smell/taste disturbances. CRP serum level was lower in the treatment group at the end of two weeks, and lymphocyte counts were significantly higher in the intervention group	5
Saber-Moghaddam, Iran, 2020 [35]	Open-label non-randomized placebo-controlled clinical trial [IRCT20200408046990N1] Treatment duration: 2 weeks Follow-up: 2 weeks after treatment	21 mild to moderate COVID-19 patients	20 mild to moderate COVID-19 patients	55.9 ± 15.16	65.9%	Sinacurcumin® soft gel 40 mg -The intervention group received 2 soft gels after breakfast and 2 soft gels after dinner daily for 2 weeks. -Control group received 2 soft gel placebos twice daily after meal	Positive effect of curcumin therapy. Symptoms resolved significantly faster in the intervention group. Duration of supplemental O2 use and hospitalization also shorter in the treatment group	3
Valizadeh, Iran, 2020 [36]	Randomized, double-blind, placebo-controlled clinical trial [IR.TBZMED.REC.1398.1314] Treatment duration: 2 weeks	20 COVID-19 patients	20 COVID-19 patients + 40 healthy subjects	51.5 ± 8.2	76.2%	Sinacurcumin® soft gel 40 mg -Intervention group received 160 mg nano-curcumin in four 40 mg capsules daily for 14 days. -Control group received the placebo capsule+ Both groups received: Betaferon 300 μg subcutaneously every other day until 5 days, Bromhexine 8 mg tablets every 8 h, and Atorvastatin 40 mg daily.	Positive effect of curcumin therapy. Nano-curcumin, as an anti-inflammatory herbal-based agent, may be able to modulate the increased rate of inflammatory cytokines (especially IL-1β and IL-6 mRNA expression and cytokine secretion) in COVID-19 patients, which may cause improvement in clinical manifestation and overall recovery	3
Tahmasebi, Iran, 2020 [37]	Randomized, double-blind, placebo-controlled Clinical trial [IR.TBZMED.REC.1398.1314] Treatment duration: 3 weeks	40 mild and severe COVID-19 patients	40 mild and severe COVID-19 patients + 40 healthy subjects	54.2 ± 9.1	60%	SinaCurcumin® (Exir Nano) 80 mg -Intervention group received an 80 mg capsule two times daily (every 12 h) for 21 days. -Placebo group received a placebo capsule two times daily (every 12 h) for 21 days	Curcumin reduced the frequency of Th17 cells and related inflammatory factors in both mild and severe COVID-19 patients. Hence, it could be considered as a potential modulatory compound in improving patient inflammation	5
Tahmasebi, Iran, 2021 [38]	Randomized, double-blind, placebo-controlled Clinical trial [IR.TBZMED.REC.1398.1314] Treatment duration: 3 weeks	40 mild and severe COVID-19 patients	40 mild and severe COVID-19 patients + 40 healthy subjects	54.2 ± 9.1	60%	SinaCurcumin® (Exir Nano) 80 mg -Intervention group received an 80 mg capsule two times daily (every 12 h) for 21 days. -Placebo group received a placebo capsule two times daily (every 12 h) for 21 days	In both mild and severe COVID-19 patients, nano-curcumin upregulated frequency of Treg cells, expression levels of FoxP3, IL-10, IL-35, and TGF-β, as well as serum levels of cytokines in the treatment group	4
Pawar, India, 2020 [39]	Randomized double-blind placebo-controlled clinical trial [CTRI/2020/05/025482] Treatment duration: 2 weeks	70 mild to severe COVID-19 patients; Mild (n = 30) Moderate (n = 25), and severe (n = 15) -Mild: (SpO2 > 94%) -moderate: (SpO2, between 90–94%) -Severe: (SpO2 < 90%)	70 mild to severe COVID-19 patients; Mild (n = 30) Moderate (n = 25), and severe (n = 15)	Range (18–85)	70.7%	Curcumin administered with piperine -Intervention group received Curcumin (252 mg) Complex® (SamiDirect, India) dietary with (2.5 mg) Bioperine® (SamiDirect, India) twice a day for 14 days from the day of admission. -Control group received a dose of probiotics (Nutrolin B Plus, which contains lactic acid Bacillus and Vitamin B; Ciplamed) twice a day for 14 days.	Positive effect of curcumin therapy. Showed early symptomatic recovery and could substantially reduce the duration of hospitalization in patients with moderate to severe symptoms, and fewer deaths observed in the intervention group	5

* In all trials, patients received standard of care based on the national COVID-19 guidelines. Investigational interventions are listed in the table.