Effects of Rice Bran Supplementation on Metabolic Syndrome-Related Parameters: A Systematic Review and Meta-Analysis
Abstract
1. Introduction
2. Materials and Methods
2.1. Search Strategy
2.2. Study Selection and Eligibility Criteria
2.3. Data Extraction
2.4. Risk of Bias Assessment
2.5. Quality of Evidence Assessment
2.6. Data Analysis
3. Results
3.1. Search Results
3.2. Study Characteristics and Risk of Bias Assessment
3.3. Effects of Rice Bran on MetS-Related Parameters
3.3.1. Effects of Rice Bran on Anthropometric Parameters
Effect of Rice Bran on Body Mass Index Levels
Effect of Rice Bran on Waist Circumference
3.3.2. Effects of Rice Bran on Blood Pressure Parameters
Effect of Rice Bran on Systolic Blood Pressure
Effect of Rice Bran on Diastolic Blood Pressure
3.3.3. Effects of Rice Bran on Glycemic Parameters
Effect of Rice Bran on Fasting Blood Glucose
Effect of Rice Bran on HbA1c
Effect of Rice Bran on Insulin Levels
3.3.4. Effects of Rice Bran on Lipid Profiles
Effect of Rice Bran on Triglyceride Levels
Effects of Rice Bran on Total Cholesterol Levels
Effect of Rice Bran on LDL-C Levels
Effect of Rice Bran on HDL-C Levels
3.4. Subgroup Analysis
3.4.1. Participants’ Health Conditions
3.4.2. Rice Bran Dosage (≥20 g/d, <20 g/d, or Oryzanol)
3.4.3. Duration of the Intervention (≥90 Days or <90 Days)
3.5. Meta-Regression Analysis
3.6. Results of Quality of Evidence Assessment
4. Discussion
5. Conclusions
Supplementary Materials
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Abbreviations
BMI | Body mass index |
BP | Blood pressure |
CI | Confidence interval |
FBG | Fasting blood glucose |
GRADE | Grading of Recommendations Assessment, Development, and Evaluation |
HbA1c | Hemoglobin A1C |
HDL-C | High-density lipoprotein cholesterol |
HMG-CoA | β-hydroxy-β-methylglutaryl-CoA |
I2 | I-squared statistic |
LDL-C | Low-density lipoprotein cholesterol |
MetS | Metabolic syndrome |
PRISMA | Preferred Reporting Items for Systematic Reviews and Meta-Analyses |
RCTs | Randomized controlled trials |
ROB2 | Risk of Bias 2 Tool |
SBP | Systolic blood pressure |
SD | Standard deviation |
SE | Standard error |
VLDL | Very-low-density lipoprotein |
WMD | Weighted mean difference |
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Author (Year) | Country | Participants | Intervention | Control | Duration (Days) | Risk of Bias Assessment | |||||
---|---|---|---|---|---|---|---|---|---|---|---|
D1 | D2 | D3 | D4 | D5 | Overall | ||||||
Accinni (2006) [29] | Italy | Dyslipidemic individuals | Oryzanol (0.040 g/d) | Placebo (rice starch) | 120 | ||||||
Balters (1981) [30] | United States of America | Healthy individuals | Basal diet with rice bran (20 g/d) | Placebo (Basal diet) | 34 | ||||||
Borresen (2016) [31] | United States of America | Colorectal cancer patients | Rice bran powder (30 g/d) | Placebo (rice starch) | 28 | ||||||
Bumrungpert (2019) [32] | Thailand | Hyperlipidemic individuals | Rice bran oil (30 mL) | Oil without rice bran | 28 | ||||||
Cheng (2010) [33] | Taiwan | Type 2 diabetes patients | Rice bran oil (3.9 g/d) | Placebo (milled rice flour) | 84 | ||||||
Choi (2014) [34] | Korea | Healthy individuals | Rice bran fermented (3 g/d) | Placebo (rice starch) | 56 | ||||||
De Lellis (2024) [35] | Italy | Dyslipidemic individuals | ROSSOPURO® Forte with γ-Oryzanol (0.062 g/d) | Placebo | 84 | ||||||
Gerhardt (1998) [36] | United States of America | Hypercholesterolemic individuals | Medium-grain rice bran product (84 g/d) | Placebo (rice starch) | 42 | ||||||
Ghorbani (2025) [37] | Iran | Metabolic syndrome individuals | Standard diet with rice bran powder (15 g/d) | Standard diet without rice bran powder | 56 | ||||||
Ito (2015) [38] | Japan | Obese individuals with hypercholesterolemia | Rice bran acylated steryl glucosides (0.05 g/d) | Placebo (rice starch) | 84 | ||||||
Kim (2008) [39] | Korea | Healthy overweight individuals | Conjugate linoleic acid with oryzanol (0.3 g/d) | Conjugate linoleic acid | 84 | ||||||
Lai (2012) [40] | Taiwan | Type 2 diabetes patients | Rice bran oil-modified milk (18 g/d) | Placebo (rice starch) | 35 | ||||||
Lin (2020) [19] | Taiwan | Metabolic syndrome and healthy individuals | Refined rice bran (20 g/d) | Refined oil without rice bran | 56 | ||||||
Mahdavi-Roshan (2024) [41] | Iran | Metabolic syndrome individuals | Standard diet with rice bran oil (30 g/d) | Standard diet without rice bran oil | 56 | ||||||
Malve (2010) [42] | India | Hyperlipidemic individuals | Rice bran oil (16.67 g/d) | Blend oil without rice bran oil | 90 | ||||||
Most (2005) [43] | United States of America | Hypercholesterolemic individuals | Rice bran oil diet (56 g/d) | Control oil blend diet | 70 | ||||||
Nhung (2016) [44] | Vietnam | Hypercholesterolemic individuals | Pre-germinated brown rice bran extract (50 g/d) | Placebo (rice starch) | 180 | ||||||
Nikooyeh (2023) [45] | Iran | Type 2 diabetes patients | Oryzanol-fortified canola oil (30 g/d) | Unfortified canola oil (without oryzanol) | 84 | ||||||
Ogawa (2019) [46] | Japan | High–normal-blood-pressure individuals | Processed rice bran (1 g/d) | Placebo (rice starch) | 84 | ||||||
Ogawa (2018) [47] | Japan | High–normal-blood-pressure and mild hypertension individuals | Thermolysin digested rice bran (1 g/d) | Placebo | 84 | ||||||
Qureshi (2001) [48] | United States of America | Hypercholesterolemic individuals | Tocotrienol-rich fraction (0.2 g/d) | AHA Step−1 diet | 35 | ||||||
Qureshi (2002) [49] | United States of America | Hypercholesterolemic individuals | Tocotrienol-rich fraction (0.2 g/d) | AHA Step−1 diet | 35 | ||||||
Saphyakhajorn (2022) [50] | Thailand | Overweight/obese individuals with hypercholesterolemia | Defatted rice bran (30 g/d) | Placebo | 84 | ||||||
Umin (2015) [51] | Japan | Type 2 diabetes patients | Rice bran oil (8.2 g/d) | Placebo | 84 | ||||||
Upadya (2015) [52] | India | Hyperlipidemic individuals | Blend oil with rice bran oil (1 L/person/ month) | Blend oil without rice bran oil | 90 | ||||||
Zavoshy (2012) [53] | Iran | Hyperlipidemic individuals | Low-calorie diet with rice bran oil (30 g/d) | Low-calorie diet without rice bran oil | 70 |
Patient or Population: Participants with Metabolic Syndrome-Related Parameters Intervention: Rice Bran and Its Bioactive Compound Comparison: Control Group | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Study Design | No. of Studies | Certainty Assessment | No. of Participants | Effect | |||||||
Risk of Bias | Inconsistency | Indirectness | Imprecision | Other Considerations | Rice Bran and Its Bioactive Compound | Control | Estimation of Absolute Effects | Certainty | |||
Relative (95% CI) | Absolute (95% CI) | ||||||||||
Body Mass Index | |||||||||||
RCT | 11 | Serious a | Not serious | Not serious | Serious b | None | 278 | 273 | - | MD 0.009 higher (0.413 lower to 0.432 higher) | ⨁⨁◯◯ Low |
Waist Circumference | |||||||||||
RCT | 8 | Serious a | Not serious | Not serious | Serious d | None | 217 | 206 | - | MD 0.332 lower (1.975 lower to 1.424 lower) | ⨁⨁◯◯ Low |
Systolic Blood Pressure | |||||||||||
RCT | 10 | Serious e | Not serious | Not serious | Not serious | None | 304 | 285 | - | MD 3.336 lower (5.248 lower to 1.311 higher) | ⨁⨁⨁◯ Moderate |
Diastolic Blood Pressure | |||||||||||
RCT | 8 | Serious f | Very serious g | Not serious | Not serious | None | 230 | 212 | - | MD 3.145 lower (5.690 lower to 0.600 lower) | ⨁◯◯◯ Very low |
Fasting Blood Glucose | |||||||||||
RCT | 10 | Not serious | Not serious | Not serious | Very serious h | None | 268 | 246 | - | MD 0.670 lower (4.844 lower to 3.505 higher) | ⨁⨁◯◯ Low |
Hemoglobin A1c | |||||||||||
RCT | 8 | Serious a | Very serious i | Not serious | Not serious | None | 195 | 188 | - | MD 0.199 lower (0.332 lower to 0.067 lower) | ⨁◯◯◯ Very low |
Insulin Level | |||||||||||
RCT | 5 | Not serious | Not serious | Not serious | Very serious j | None | 104 | 103 | - | MD 0.132 lower (1.098 lower to 0.834 higher) | ⨁⨁◯◯ Low |
Triglycerides | |||||||||||
RCT | 19 | Serious a | Very serious g | Not serious | Very serious k | None | 459 | 440 | - | MD 7.570 lower (16.714 lower to 1.573 higher) | ⨁◯◯◯ Very low |
Total Cholesterol | |||||||||||
RCT | 21 | Serious a | Very serious g | Not serious | Not serious | Publication bias strongly suspected c | 517 | 495 | - | MD 13.594 lower (20.289 lower to 6.900 lower) | ⨁◯◯◯ Very low |
Low-Density Lipoprotein | |||||||||||
RCT | 22 | Serious e | Very serious g | Not serious | Not serious | none | 536 | 512 | - | MD 14.580 lower (21.124 lower to 8.036 lower) | ⨁◯◯◯ Very low |
High-Density Lipoprotein | |||||||||||
RCT | 20 | Serious a | Very serious g | Not serious | Not serious | none | 487 | 467 | - | MD 3.074 lower (0.829 higher to 5.319 higher) | ⨁◯◯◯ Very low |
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Tantayakhom, S.; Inpan, R.; Yaja, K.; Koonrungsesomboon, N.; Teekachunhatean, S.; Na Takuathung, M. Effects of Rice Bran Supplementation on Metabolic Syndrome-Related Parameters: A Systematic Review and Meta-Analysis. Int. J. Mol. Sci. 2025, 26, 9051. https://doi.org/10.3390/ijms26189051
Tantayakhom S, Inpan R, Yaja K, Koonrungsesomboon N, Teekachunhatean S, Na Takuathung M. Effects of Rice Bran Supplementation on Metabolic Syndrome-Related Parameters: A Systematic Review and Meta-Analysis. International Journal of Molecular Sciences. 2025; 26(18):9051. https://doi.org/10.3390/ijms26189051
Chicago/Turabian StyleTantayakhom, Sirapatsorn, Ratchanon Inpan, Kantirat Yaja, Nut Koonrungsesomboon, Supanimit Teekachunhatean, and Mingkwan Na Takuathung. 2025. "Effects of Rice Bran Supplementation on Metabolic Syndrome-Related Parameters: A Systematic Review and Meta-Analysis" International Journal of Molecular Sciences 26, no. 18: 9051. https://doi.org/10.3390/ijms26189051
APA StyleTantayakhom, S., Inpan, R., Yaja, K., Koonrungsesomboon, N., Teekachunhatean, S., & Na Takuathung, M. (2025). Effects of Rice Bran Supplementation on Metabolic Syndrome-Related Parameters: A Systematic Review and Meta-Analysis. International Journal of Molecular Sciences, 26(18), 9051. https://doi.org/10.3390/ijms26189051