Rice Protein
Brown Rice Protein — DIAAS ~0.37–0.57 · Arsenic risk · Best used in pea+rice blends
Unregulated by FDA
for efficacy/purity
Version 2025-04 · Last Reviewed April 1, 2025
About this review (v2025-04, last reviewed April 1, 2025): This review was compiled from peer-reviewed clinical trials, independent laboratory analyses, and regulatory filings. Supplement manufacturers had no editorial input. Funding sources for cited studies are disclosed where available. Read our full methodology
This content is for educational purposes only. Supplements are not FDA-approved to treat, cure, or prevent any disease. Discuss supplementation with your healthcare provider before starting, especially if you take medications.
What it is
Brown rice protein is extracted from whole grain brown rice after enzymatic digestion of starch. It is low in lysine — the essential amino acid most lacking in grain proteins — and has the lowest DIAAS score of any commercially common protein supplement (0.37–0.57). However, it is vegan, hypoallergenic, and digestively very well tolerated, making it a valuable component of pea+rice blends.
Why form matters
Rice protein's amino acid gap (low lysine, adequate methionine) is complementary to pea protein's gap (adequate lysine, low methionine). This is why pea+rice is the most scientifically supported plant protein combination: together they approach a complete amino acid profile. Used alone, brown rice protein's DIAAS score is too low to reliably serve as a primary protein source for muscle protein synthesis. The arsenic concern is specific to brown rice — more concentrated than white rice — and scales with dose.
Molecular Forms — What the Research Actually Used
The form in the bottle determines how much actually reaches your bloodstream.
Absorption: Moderate-rapid
Most commercially available form. Gritty texture. Low lysine. Best used as 30–40% of a pea+rice blend rather than as a sole protein source. Arsenic content varies significantly by growing region.
Absorption: Moderate-rapid
The recommended form for plant protein supplementation. Pea compensates for rice's lysine gap; rice compensates for pea's methionine gap. The combined DIAAS of a well-formulated blend approaches 0.9+.
Dosing — What the Research Used
In pea+rice blend (primary use)
Joy et al. 2013; Gorissen et al. 2018
Standalone use — not recommended as primary protein source
Gorissen et al. 2018; WHO protein quality standards
Note: Never use rice protein as a sole protein source for sustained muscle building. The lysine deficiency will limit muscle protein synthesis regardless of dose. In a properly formulated pea+rice blend with at least 40% pea protein, the product becomes a viable complete protein substitute. Verify heavy metal testing for any rice protein product.
Frequently Asked Questions About Rice Protein
- What is Rice Protein?
- Brown rice protein is extracted from whole grain brown rice after enzymatic digestion of starch. It is low in lysine — the essential amino acid most lacking in grain proteins — and has the lowest DIAAS score of any commercially common protein supplement (0.37–0.57). However, it is vegan, hypoallergenic, and digestively very well tolerated, making it a valuable component of pea+rice blends.
- What does Rice Protein do?
- Rice protein alone is an incomplete protein source with a DIAAS of 0.37–0.57 — insufficient for meeting muscle protein synthesis requirements as a sole protein source due to lysine limitation. When combined with pea protein in a 50/50 or 60/40 blend, the combined amino acid profile approaches complete status and produces muscle mass outcomes comparable to whey in resistance training studies (Joy et al. 2013). Use in blends; verify heavy metal testing.
- What is the typical dose of Rice Protein?
- Never use rice protein as a sole protein source for sustained muscle building. The lysine deficiency will limit muscle protein synthesis regardless of dose. In a properly formulated pea+rice blend with at least 40% pea protein, the product becomes a viable complete protein substitute. Verify heavy metal testing for any rice protein product.
- Does Rice Protein interact with any medications?
- Rice Protein has known interactions with: Levothyroxine (Synthroid) — Protein meals affect levothyroxine absorption timing. Take thyroid medication 30–60 min before any protein supplement..
- Who should be cautious about taking Rice Protein?
- Exercise caution or consult a healthcare provider if you are: Children and pregnant women — the FDA specifically warns about arsenic risk from brown rice consumption in these groups. High-dose brown rice protein supplementation amplifies this concern.; Sole protein source — lysine deficiency risk; must combine with lysine-rich protein sources.; Heavy metal sensitive individuals — arsenic content in brown rice protein varies significantly by brand and source. Only use independently heavy-metal-tested products..
Get notified when we update Rice Protein
We'll email you when new evidence, safety updates, or alternatives are added.
No spam. Unsubscribe anytime.