Science & Testing

Evidence at a glance

  • 2 Human trials
  • 1.0 PDCAAS score
  • 2 Lab Studies

Featured human studies

Real people; Real results

  • Human Study

    Yeast matched whey in an 8-week resistance-training trial

    Adults on an 8-week resistance-training program who took yeast protein gained lean muscle and strength similar to those who took whey.

    What it may mean

    If whey doesn't sit well with you, yeast protein may be a comparable way to support your training.

    Important context

    This trial shows yeast protein performed similarly to whey, not better, and results also depend on training, overall diet and the individual.

    VS. WheyMuscle and strength gains similar to whey

    Yeast protein 1.83LB
    Whey protein 1.63LB
    Lean mass gained over 8 weeks
    Participants
    79
    Duration
    8 Weeks
    Details
    Randomized • Placebo-controlled • Double-blind
    Publication
    Journal of Food and Nutrition Research
    Read the study

    Briskey, D., Skinner, R. A., Zhang, H., Chen, Z., & Rao, A. (2024). Effect of yeast protein on muscle mass and performance in an adult population—A double-blind, randomised controlled trial. Journal of Food and Nutrition Research, 12(5), 292–300.

  • Human Study

    Improved walking and physical function after only 6 months

    After six months of taking yeast protein, participants showed improvements on walking and physical-function tests.

    What it may mean

    Getting enough quality protein every day may help support everyday strength and mobility over time.

    Important context

    Physical-function results can be influenced by exercise, overall diet and the group studied.

    Be Better.Improvements in walking and physical function

    Yeast protein 0.9
    Whey protein 0.3
    Physical performance · SPPB score change
    Participants
    92 • Avg Age: 73
    Duration
    6 months
    Details
    Randomized • Placebo-controlled • Double-blind
    Publication
    Food Science & Nutrition
    Read the study

    Bai, H., Shen, L., Zhao, F., Li, S., Tan, L., Gong, Q., Gu, D., Sun, J., & Ma, J. (2026). The impact of oral whey protein and yeast protein supplementation for 6 months on skeletal muscle mass, strength, and function in the elderly: A randomized, controlled, parallel study. Food Science & Nutrition, 14(3), e71552.

Complete essential amino-acid profile

ProteinRx provides 47.3 g of essential amino acids per 100 g of protein, compared with 45.7 g for whey.

PDCAAS 1.0, and what that score can't tell you. PDCAAS (Protein Digestibility Corrected Amino Acid Score) rates protein quality from 0 to 1.0 based on amino acid content and digestibility. Yeast protein scores 1.0. But the score is capped at 1.0, so it can't show differences between proteins that reach the top, and newer methods like DIAAS aim to measure digestibility more precisely. Think of it as a pass mark, not a ranking.

  • 9 of 9 Essential amino acidsAll nine amino acids your body can't make on its own.
  • 1.0 PDCAAS scoreThe top of the scale, the same score as whey.
  • 3.2 g Leucine per 30 g proteinThe amino acid most closely linked to muscle building.

Digestion research

Early research looks at how yeast protein breaks down and how it may interact with your gut.

  • Laboratory Study

    Yeast Protein scores similar to whey and better than plant.

    Yeast protein delivered all nine essential amino acids, earned a maximum PDCAAS of 1.0 and outscored every plant protein tested.

    What it may mean

    Our bodies need to get essential amino acids from food, but they're not all equal in quality. Tested side by side against five other proteins, yeast protein matched whey at the top—delivering all nine essential amino acids in higher concentrations than soy, pea, or wheat.

    Read the study

    Cao et al. (2025). Evaluation of the nutritional quality of yeast protein in comparison to animal and plant proteins using growing rats and INFOGEST model. Food Chemistry, 463, 141178.

  • Laboratory Study

    Digested like dairy. Made without it.

    In a sophisticated model of human digestion, yeast protein was broken down and made amino acids available at levels comparable to whey and casein.

    What it may mean

    A complete amino-acid list only matters if your digestive system can unlock it. Researchers put yeast protein, whey and casein through a five-hour simulation of the human stomach and small intestine. The yeast protein kept pace with both dairy proteins—showing that this new source can deliver more than impressive numbers on a label.

    Read the study

    Caron et al. (2025). In vitro human gastrointestinal digestibility and colonic fermentation of edible yeast-based protein: A comparative study with whey and casein. Food Research International, 208, 116098.

Third-party testing

Every batch of ProteinRx is tested for protein content, purity and safety. Here's what we test, why it matters and how to read the results.

  • Protein content

    Confirms each scoop delivers the protein on the label.

  • Heavy metals

    Screens for lead, cadmium, arsenic and mercury, a common concern with protein powders.

  • Microbial safety

    Checks for harmful bacteria, yeast and mold so every batch is safe to eat.

Latest test results

How to read a report

  • Match the lot number on the report to the lot printed on your pouch.
  • Compare each result to its limit. A result below the limit is a pass.
  • "ND" or "<LOQ" means the amount was too low for the lab to detect or measure.
  • Check the lab name and date so you know who tested it and when.

Science FAQ

Is yeast protein a complete protein?

Yes. It contains all nine essential amino acids and has a PDCAAS score of 1.0, the same as whey.

Is yeast protein the same as nutritional yeast?

No. Nutritional yeast is a savory seasoning. Yeast protein isolate is a concentrated protein ingredient with a much milder taste and far more protein per serving.

Is ProteinRx plant-based?

Neither plant nor animal. Yeast belongs to the fungal kingdom, so ProteinRx is a dairy-free, vegan protein from a completely different source.

How strong is the research on yeast protein?

Promising, but still early. There are two human trials plus laboratory research. We label every study by type and show what it doesn't prove, so you can judge for yourself.

I'm concerned about Candida. Is yeast protein right for me?

ProteinRx is made from food-grade yeast, the same species used for bread, which is different from Candida. If you have concerns about Candida or a yeast sensitivity, check with your healthcare provider before trying it.

Where can I see test results?

Lab reports are posted in the Latest test results section above. Match the lot number on your pouch to find your batch.

Ready to try ProteinRx?

30g of complete yeast protein per serving. Not whey. Not pea. Not soy.

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