**Background:** Dyslipidemia is a multifactorial disorder characterized by elevated total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and/or decreased high-density lipoprotein cholesterol (HDL-C). It is a major risk factor for cardiovascular disease, the leading cause of death from non-communicable diseases. Dietary interventions are first-line treatment. Rice bran (RB) is a nutraceutical rich in fiber (20–51%), plant sterols, oleic acid (38.4%), linoleic acid (34.4%), and bioactive compounds such as γ-oryzanol, which has cholesterol-lowering properties. Previous studies on RB and lipid profiles have yielded contradictory results, and no meta-analysis had examined whole RB (as opposed to RB oil).
**Methods:** A systematic literature search was conducted in PubMed/Medline, Scopus, ISI Web of Science, and Google Scholar up to June 2022, without language or time restrictions. Eligible studies were RCTs (parallel or crossover) in adults (≥18 years) that investigated whole RB, stabilized RB, or RB powder versus a control group and reported at least one lipid outcome (TC, TG, LDL-C, HDL-C). Studies examining RB oil, isolated RB components, defatted RB, or RB combined with other interventions were excluded. Data were pooled using a random-effects model and reported as weighted mean difference (WMD) with 95% confidence intervals (CIs). Heterogeneity was assessed using Cochrane's Q test and I² statistic. Subgroup analyses were pre-specified for baseline lipid levels, country, study design, age, trial duration, RB dose, health status, sex, and baseline BMI. Non-linear dose–response analysis used fractional polynomial modeling. Meta-regression examined linear associations between dose/duration and effect size. Risk of bias was assessed using the Cochrane RoB 2.0 tool, and evidence certainty was evaluated using GRADE.
**Key Results:** Eight RCTs (11 effect sizes) with 472 participants (286 intervention, 186 control) were included. Mean age ranged from 37 to 62 years, BMI from 24.43 to 28.7 kg/m², and trial duration from 3 to 12 weeks. RB doses ranged from 20 to 100 g/day. The overall meta-analysis found no significant effects of RB supplementation on any lipid outcome:
- TG: WMD -11.38 mg/dl (95% CI: -27.73, 4.96; P = 0.17; I² = 79.5%, P < 0.001)
- TC: WMD -0.68 mg/dl (95% CI: -7.25, 5.88; P = 0.834; I² = 79.5%, P < 0.001)
- LDL-C: WMD -1.68 mg/dl (95% CI: -8.46, 5.09; P = 0.627; I² = 81.2%, P < 0.001)
- HDL-C: WMD 0.16 mg/dl (95% CI: -1.52, 1.85; P = 0.848; I² = 60.3%, P = 0.005)
Subgroup analyses showed a significant TG reduction in studies involving both sexes (WMD: -22.80 mg/dl; 95% CI: -43.27, -2.34; P = 0.029), overweight individuals (BMI 25–29.9 kg/m²; WMD: -24.73 mg/dl; 95% CI: -41.02, -8.45; P = 0.003), and participants <50 years (WMD: -27.58 mg/dl; 95% CI: -49.01, -6.15; P = 0.012). For HDL-C, studies conducted in the USA (WMD: -1.50 mg/dl; 95% CI: -1.90, -1.10; P < 0.001), crossover studies (WMD: -1.48 mg/dl; 95% CI: -1.88, -1.08; P < 0.001), and studies in hypercholesterolemic patients (WMD: -1.45 mg/dl; 95% CI: -1.85, -1.06; P < 0.001) showed a significant decrease in HDL-C. Non-linear dose–response analysis indicated that RB dose significantly altered TG (P for nonlinearity = 0.035), TC (P = 0.001), and LDL-C (P = 0.023), but not HDL-C (P = 0.359). Duration significantly affected LDL-C (P = 0.005) but not TG (P = 0.256) or HDL-C (P = 0.222); TC was borderline (P = 0.054). Meta-regression found no significant linear association between dose or duration and any lipid outcome. Sensitivity analysis showed no single study drove the overall results, except for HDL-C where omitting Tazakori et al. changed the effect to significant (WMD: -1.46 mg/dl; 95% CI: -1.85, -1.07). No publication bias was detected. GRADE assessment rated the quality of evidence as low for all outcomes due to high heterogeneity and non-significant results.
**Clinical Implications:** This meta-analysis does not support the use of whole rice bran supplementation as an effective intervention for improving lipid profiles in adults. The null findings contrast with positive results from meta-analyses of rice bran oil, suggesting that the lipid-lowering effects of RB may be primarily attributable to its oil fraction (rich in γ-oryzanol, vitamin E, and unsaturated fatty acids) rather than the whole bran matrix. The significant subgroup findings (e.g., TG reduction in younger, overweight, mixed-sex populations) are hypothesis-generating but based on small numbers and should be interpreted cautiously. The low quality of evidence, small sample sizes, short durations (most ≤4 weeks), and high heterogeneity limit confidence in these findings. Clinicians should not recommend rice bran as a lipid-lowering therapy based on current evidence. Future research requires larger, longer-term, placebo-controlled RCTs with standardized RB doses and rigorous blinding to determine whether specific populations or dosing strategies might yield clinically meaningful benefits.