Table 2.

Meta-analyses of RCTs investigating the effect of curcumin intake on antioxidant activity.

Ref.	No. of Studies Included	Health Status of Subjects	No. of Subjects	Age of Subjects (Years)	Design	Period (Weeks)	Dose	Outcomes (Effect Size)	Quality of Primary Studies	Databases
Qiu et al. 2023 [22]	2 publications [26,27]	Mets	165	34–64	P	6–12	80 mg/day of nano-curcumin, 1000 mg/day of curcuminoids	↓ MDA (MD = −2.35 µmol/L; 95% CI −4.47 to −0.24; p = 0.03)	Cochrane risk of bias tool (71.4%)	PubMed, SCOPUS, Cochrane Library, EMBASE, Web of Science, and China Biological Medicine
Dehzad et al. 2023 [42]	16 publications [23,30,43,49,57,68,76,77,78,79,80,82,88,143,144,145]	Mets, obese, T2DM, prostate cancer, PUD, NAFLD, hemodialysis, infertile men, β-thalassemia, hyperlipidemia, coronary elective angioplasty, DFU, healthy	857	18–70	P	4–12	80–3000 mg/day of curcumin, 2000–3000 mg/day of turmeric	↑ TAC (WMD = 0.21 mmol/L; 95% CI 0.08 to 0.33; I2 = 99.6%; p < 0.001)	Cochrane risk of bias tool (84.2%)	PubMed, Scopus, Web of Science, Cochrane Library, and Google Scholar
	18 publications [23,43,53,57,60,68,76,77,78,79,80,81,82,92,98,143,144,146]	Mets, hemodialysis, chronic pulmonary complications, T2DM, knee OA, beta-thalassemia, healthy, Takayasu arteritis, infertile men, NAFLD, HIV, hyperlipidemia, coronary elective angioplasty, DFU	1475	18–70	P	4–16	80–1500 mg/day of curcumin, 1500 mg/day of curcuminoids, 1500–3000 mg/day of turmeric	↓ MDA (WMD = −0.33 µmol/L; 95% CI −0.53 to −0.12; I2 = 99.6%; p < 0.001)
	7 publications [60,63,64,79,95,145,147]	T2DM, solid tumor, prostate cancer, chronic pulmonary complications, PCOS, coronary elective angioplasty, chronic bronchial asthma	497	18–70	P	4–12	80–3000 mg/day of curcumin, 180–1500 mg/day of curcuminoids	↑ SOD (WMD = 20.51 u/L; 95% CI 7.35 to 33.67; I2 = 95.4%; p < 0.001)
Jakubc-zyk et al. 2020 [148]	3 publications [43,109,143]	Overweight/obese, infertile, β-thalassemia major patients	177	13–45	P	10–12	80–1000 mg/day of curcumin	↑ TAC (SMD = 2.696; Z = 2.003; 95% CI = 0.058 to 5.335; p = 0.045)	Cochrane risk of bias tool (57.1%)	PubMed/MEDLINE and Embase
	3 publications [43,109,143]	Overweight/obese, infertile, β-thalassemia major patients	177	13–45	P	10–12	80–1000 mg/day of curcumin	↔ MDA (SMD = −1.579, Z = −1.714, CI = 95%, p = 0.086)
Tabrizi et al. 2019 [125]	5 publications [27,57,110,114,124]	Mets, T2DM, coronary vascular artery	425	18–70	P	3 days– 8 weeks	300–4000 mg/day of curcuminoids, 2000 mg/day of turmeric	↓ MDA (SMD = −3.14; 95% CI −4.76 to −1.53; p < 0.001)	Cochrane risk of bias tool (82.9%)	Cochrane Library, Embase, PubMed, and Web of Science
	3 publications [27,124,149]	Mets, obese, T2DM,	260	18–65	P	4–8	1000 mg/day of curcuminoids	↔ SOD (SMD 0.34; 95% CI −1.06 to 1.74, p = 0.63)
Alizadeh et al. 2019 [150]	12 publications [27,43,98,124,143,151,152,153,154,155,156,157]	Mets, knee OA, T2DM, healthy, infertile oligoasthenospermia, non-diabetic or diabetic proteinuric CKD, chronic gastritis, β-thalassemia, hemodialysis, sulfur mustard Iraq–Iran war chronic pulmonary complications, solid cancer	1005	20–75	P	1–16	80–1000 mg/day of curcumin, 90–1500 mg/day of curcuminoids, 1500–2100 mg/day of turmeric	↓ MDA (SMD = −0.46; 95% CI −0.68 to −0.25)	Cochrane risk of bias tool (59.0%)	PubMed, Embase, Cochrane Central, Scopus, and Google Scholar
	7 publications [62,124,141,145,155,156,158]	Healthy, prostate cancer treated with radiotherapy, veterans of the Iraq–Iran war with chronic pruritus, sulfur mustard Iraq–Iran war chronic pulmonary complications, solid cancer, Mets, knee OA, T2DM	618	35–79	P	4–12	900–3000 mg/day of curcuminoids	↑ SOD (SMD = 0.82; 95% CI 0.27 to 1.38)
	5 publications [62,141,143,145,155]	Healthy, prostate cancer treated with radiotherapy, β-thalassemia, veterans of the Iraq–Iran war with chronic pruritus, solid cancer	322	20–79	P	4–12	900–3000 mg/day of curcuminoids	↑ CAT (SMD = 10.26; 95% CI 0.92 to 19.61)
	5 publications [62,141,145,151,158]	Non-diabetic or diabetic proteinuric CKD, prostate cancer treated with radiotherapy, veterans of the Iraq-Iran war with chronic pruritus, occupational stress-related anxiety and fatigue	357	26–79	P	4–12	320–782 mg/day of curcumin, 1000–3000 mg/day of curcuminoids	↑ GPx (SMD = 8.90; 95% CI 6.62 to 11.19)
	6 publications [43,88,143,145,152,157]	PUD, infertile oligoasthenospermia, prostate cancer treated with radiotherapy, β-thalassemia, chronic gastritis, healthy	330	22–79	P	1–12	80–1500 mg/day of curcumin, 90–3000 mg/day of curcuminoids	↔ TAC (SMD = 0.30; 95% CI −0.20 to 0.81)
	1 publication [151]	Non-diabetic or diabetic proteinuric CKD	101	37–57	P	8	320 mg/day of curcumin	↔ GR (SMD = −0.01; 95% CI −0.03 to 0.02)
Qin et al. 2018 [159]	7 publications [27,57,98,114,124,153,156]	T2DM, OA, Mets, end-stage renal disease	525	34–67	P	4–8	46–1000 mg/day of curcumin	↓ MDA (SMD = −0.769; 95% CI −1.059 to −0.478)	Cochrane risk of bias tool (54.2%)	PubMed, EMBASE, Web of Science, Medline Ovid, Books@Ovid, Journals@Ovid, and Cochrane Library
	4 publications [27,124,141,156]	T2DM, OA, Mets, chronic pruritic skin lesions	341	34–67	P	4–8	1000–1500 mg/day of curcumin	↑ SOD (SMD = 1.084; 95% CI 0.487 to 1.680)
	2 publications [57,153]	T2DM, end-stage renal disease	108	32–67	P	4–8	46–66.3 mg/day of curcumin	↔ GPx (SMD = 0.13; 95% CI −0.25 to 0.51)

CAT, chloramphenicol acetyltransferase; CKD, chronic kidney disease; DFU, diabetic foot ulcer; GPx, glutathione peroxidase; GR, glutathione reductase; HIV, human immunodeficiency virus; MD, mean difference; MDA, malondialdehyde; Mets, metabolic syndrome; NAFLD, non-alcoholic fatty liver disease; OA, osteoarthritis; P, parallel; PCOS, polycystic ovary syndrome; PUD, peptic ulcer disease; RCTs, randomized controlled trials; SMD, standard difference in means; SOD, superoxide dismutase; TAC, total antioxidant capacity; T2DM, type 2 diabetes mellitus; WMD, weighted mean differences. The quality of primary studies is indicated as a percentage of low risk (Cochrane risk of bias tool). ↑, increase; ↓, decrease; ↔ no effect.