Protein extracted enzymatically from brown rice, typically 70–80% protein. It is comparatively rich in methionine and cysteine and low in lysine, which makes it complementary to pea protein.
Rice protein exists mainly as a hypoallergenic option and as the other half of a pea-and-rice blend. The single trial usually cited compared 48 g of rice protein isolate with 48 g of whey alongside eight weeks of resistance training and found no significant difference in body composition or strength — a result frequently reported as "rice equals whey", when the more accurate reading is that at a large enough dose the lysine shortfall stops mattering and a small trial could not detect a difference. Rice products also carry the arsenic question that applies to rice generally.
Sold as
Isolate powder, Pea and rice blend, Ready-to-drink
Standardised to
Protein percentage, typically 70–80% — a product without this marker may not resemble what was studied.
Also known as
Brown rice protein, Rice protein isolate
Regulation: Sold as a food or dietary supplement with no pre-market efficacy review. Rice accumulates inorganic arsenic from soil and water, and independent testing has found measurable arsenic in rice protein products; several jurisdictions set limits for arsenic in rice-based foods for infants but not for adult supplements.
What the research used
The amounts, forms and durations published trials of Rice protein actually administered.
These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.
Studied for Resistance training
48 g
Limited
Rice protein isolate after training · 8 weeks
The dose in the one direct comparison against whey, which found no significant difference in outcomes. The trial was small and the dose is far larger than a typical whey serving, which is part of why the comparison came out level.
This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.
When it was taken
Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.
None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.
🔀Split through the day
Not enough
General protein distribution logic applies. Rice protein specifically has not been studied for timing.
Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.
The evidence in depth
Best supported: Limited
What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.
One small trial found 48 g of rice protein produced body composition and strength changes comparable to the same dose of whey over eight weeks. A single small study at an unusually large dose is thin ground, and rice protein is limiting in lysine at more typical servings.
Limited evidence. Early human work, or mostly lab and animal research.
Deep research mode adds each paper’s own conclusion and stated limitations.
Things to know
Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.
Worth knowing
Inorganic arsenic
Rice takes up arsenic from soil and irrigation water more than other cereals, and independent testing has found measurable inorganic arsenic in rice protein powders — in some cases enough that daily use was flagged as a concern. This is the main reason to prefer a tested product or a different protein source for daily use.
Worth knowing
Low in lysine
Rice protein is limiting in lysine, which is why it is usually blended with pea protein. Used alone at ordinary serving sizes it is a lower-quality protein than the single trial at 48 g might suggest.
Worth knowing
Heavy metals in plant proteins
Beyond arsenic, plant proteins as a group have tested higher for lead and cadmium than dairy proteins in independent programmes.
In the food catalogue
The whole-food form, where one exists. The evidence for a concentrated extract rarely transfers to the food, or the other way round — these are cross-links, not equivalents.