Rice Protein Isolate
Also known as: Brown rice protein, Oryza sativa protein, RPI
Enzymatic hydrolysis and concentration of brown rice produces 80–90% protein dry matter. Complete EAA profile but lysine-limited; DIAAS ≈ 0.59 alone, ≈ 0.95 when blended with pea.
Last reviewed: 2026-06-28 · 1 indexed study
Set your location for accurate regulatory status
Saved on this device — no sign-in needed.
Overview
Rice protein isolate is an enzymatically extracted brown-rice-derived protein (typically 80–85% by weight) with a complementary amino acid profile to pea protein: high in methionine and cysteine but lower in lysine. The two are commonly blended (70:30 pea:rice) to produce a complete vegan protein with whey-equivalent leucine and DIAAS.
Mechanism & Function
Mechanism of Action
Provides leucine-rich EAAs for mTORC1-mediated MPS; high-dose protocols (48 g) match whey for myofibrillar MPS due to higher absolute leucine delivery despite lower density.
Physiological Role
Hypoallergenic plant-protein option for those avoiding soy, dairy and pea.
Primary Pathways
Performance / Health Relevance
Joy 2013 was the landmark RCT — 48 g/day rice protein produced muscle mass, strength and body composition changes statistically equivalent to 48 g/day whey isolate over 8 weeks of resistance training in trained men.
Evidence Review
No meta-analyses or systematic reviews indexed for this ingredient yet.
Dimensions marked N/A have no indexed evidence of that class. They are shown as unavailable rather than scored.
Practical Use & Dosage
- Minimum Effective Dose
- 30 g per serving (alone)
- Optimal Range
- 30–48 g per serving alone, or 25 g as part of a pea-rice blend
- Upper / Caution Level
- Be aware of heavy-metal screening — choose third-party-tested brands; brown rice can accumulate arsenic
- Timing
- Post-exercise or split across the day
- Best Format
- Enzymatically processed isolate, ideally blended with pea isolate
- Bioavailability
- DIAAS 0.59 alone, rising to ~0.95 in a pea-rice blend.
- Absorption Considerations
- Smoother texture than pea; mildly sweet, neutral flavour.
Safety & Interactions
Side Effects
- •Generally minimal
- •Heavy-metal contamination risk if not third-party tested
Contraindications
- Rare rice allergy
Drug Interactions
- •Minimal
Who Should Avoid
- •Those with rice allergy
Monitoring
Choose Clean Label Project or similar third-party-tested brands due to brown-rice arsenic concerns.
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is Rice Protein Isolate typically used or indicated?
Rice Protein Isolate is most commonly used for: Hypoallergenic protein, Vegan MPS (with pea), Soy- and dairy-free formulations. Hypoallergenic plant-protein option for those avoiding soy, dairy and pea.
How does Rice Protein Isolate work?
Provides leucine-rich EAAs for mTORC1-mediated MPS; high-dose protocols (48 g) match whey for myofibrillar MPS due to higher absolute leucine delivery despite lower density.
What is the recommended dose of Rice Protein Isolate?
The optimal range is 30–48 g per serving alone, or 25 g as part of a pea-rice blend. with a minimum effective dose of 30 g per serving (alone). Best taken: Post-exercise or split across the day. Upper / caution level: Be aware of heavy-metal screening — choose third-party-tested brands; brown rice can accumulate arsenic.
What are the side effects of Rice Protein Isolate?
Reported side effects include: Generally minimal; and Heavy-metal contamination risk if not third-party tested. Monitoring: Choose Clean Label Project or similar third-party-tested brands due to brown-rice arsenic concerns.
Does Rice Protein Isolate interact with medications?
Known or theoretical interactions: Minimal. Always check with a clinician before combining with prescription medication.
Who should avoid Rice Protein Isolate?
Rice Protein Isolate is generally not recommended for: Those with rice allergy; and Rare rice allergy.
How strong is the evidence for Rice Protein Isolate?
Evidence level: Moderate (overall score 70/100), based on 1 indexed study on SuppIndex.
Research & References (1)
The effects of 8 weeks of whey or rice protein supplementation on body composition and exercise performance
Joy JM et al. 48 g/day rice protein matched 48 g/day whey isolate for lean mass, strength and body composition changes over 8 weeks of resistance training.
Related Ingredients
Other top-rated ingredients in Proteins & Protein Powders.
Whey Protein Isolate (WPI)
94/100Microfiltered or ion-exchange purified whey to ≥90% protein. Lower in lactose and fat than WPC, preserving most bioactive fractions in CFM versions. DIAAS ≈ 1.09; leucine content ~11%.
Whey Protein Concentrate (WPC 80)
92/100Membrane-filtered (ultrafiltration/microfiltration) liquid whey concentrated to 70–80% protein dry matter. Retains higher levels of native bioactive fractions than isolate. PDCAAS = 1.0; DIAAS ≈ 1.09.
Micellar Casein
88/100Casein retained in its native micellar form (intact αs1, αs2, β and κ caseins assembled with colloidal calcium phosphate). Coagulates at gastric pH, dramatically slowing emptying.
Research Overview
Moderate EvidenceCite this ingredient
One-click citation export in APA, MLA, Chicago, BibTeX, or HTML. The URL below is stable and safe to link.
Stable URL
https://thesuppindex.com/ingredients/rice-protein-isolate
SuppIndex. (2026). Rice Protein Isolate: Evidence summary, dosage and clinical studies. Retrieved October 16, 2026, from https://thesuppindex.com/ingredients/rice-protein-isolate
Based on 1 indexed studies · Evidence level: Moderate.
Goal Ratings
Stack Compatibility
Always pair with pea protein for a complete EAA profile and whey-equivalent leucine.