In a lab study from the UK, five plant-based chicken alternatives had 21.5 to 32.2 g of protein per 100 g, real chicken 26.0 to 33.1 g. The big difference was in quality: their DIAAS was 52 to 65, while chicken breast and thigh scored 162 and 151. The plant products were digested less well, and they lacked lysine, methionine and cysteine, or tryptophan. The authors conclude: the amount of protein alone says nothing about its nutritional value.
The study
Alotaibi et al. 2026 compared five plant-based chicken alternatives from UK supermarkets with cooked chicken breast and cooked chicken thigh. The substitutes were prepared according to the package instructions, the chicken was cooked in the oven at 180 °C for 20 to 25 minutes. Digestion was then simulated in the lab using the standardized INFOGEST method: mouth, stomach and small intestine with the matching enzymes, pH values and times.
The study doesn't name brands. The products differed in their protein base:
| Product | Main proteins according to label |
|---|---|
| P-C1 | wheat protein and pea protein |
| P-C2 | textured soy protein, soy protein concentrate |
| P-C3 | soy protein concentrate, some pea protein isolate |
| P-C4 | soy, wheat and pea protein |
| P-C5 | wheat protein, pea and potato protein |
The result
Line = 100, fully usable from this point. In vitro DIAAS, young child pattern (0.5–3 years). Data: Alotaibi et al. 2026, Table 5.
| Protein g/100 g | Digestibility | DIAAS | |
|---|---|---|---|
| Chicken breast, cooked | 33.1 | approx. 100 % | 162 |
| Chicken thigh, cooked | 26.0 | approx. 100 % | 151 |
| Plant-based alternatives, prepared | 21.5–32.2 | 81–93 % | 52–65 |
Chicken had significantly more protein, but some substitutes were on par with chicken thigh. The gap in quality was much bigger. None of the substitutes reached the mark of 75 that the FAO gives as an example of a good protein source. The authors classify them as low to medium quality, and chicken as an excellent protein source.
Why the alternatives score worse
Certain amino acids are missing. Lysine and methionine were lower in all substitutes than in chicken. Depending on the product, lysine, methionine and cysteine, or tryptophan was the scarcest amino acid. That fits the base ingredients: wheat is low in lysine, soy and pea are low in methionine.
They are digested less well. The amino acids from chicken were released practically completely in the test, those from the substitutes at 81 to 93 %. The degree to which the protein was broken down into small fragments was also much higher for chicken (according to the text, 57 to 65 % versus 20 to 35 %). The authors name possible reasons:
- the structure of plant proteins and clumping during processing
- fiber and binders such as methylcellulose, which can affect digestion
- Maillard reactions from heating
- antinutritional factors, which were not measured in the study, however
On processing, the authors write that isolating, extruding and heating can reduce protein quality, for example through breakdown of amino acids and cross-linking of proteins. According to Sharma et al. 2025, the fibrous texture of meat substitutes comes from high-moisture extrusion.
Even soy doesn't close the gap
Soy is considered the best plant protein (more on this in the article Tofu, seitan, soy milk). In this study, though, even the soy-based products stayed below 75. The authors write that the plant ingredients are naturally low in methionine and cysteine, lysine and tryptophan. Processing comes on top of that.
Protein claims on the label
One detail from the study: protein content is usually calculated from nitrogen content. The authors consider it likely that this method overestimates the protein content of the substitutes more than that of chicken. Their conclusion: the amount of protein alone doesn't reflect nutritional value.
What does this mean?
Meat substitutes provide protein, but less usable protein than the gram figure suggests. If you simply multiply amount by DIAAS (capped at 100 %), 100 g of the best substitute leaves about 18 g of usable protein, 100 g of chicken breast 33 g. If you eat mostly plant-based, the best way to make up for this is through the rest of the meal, with partners that supply the missing amino acids. More on this in the article Combining proteins.
The authors see people with higher protein needs or limited access to a variety of protein sources as most affected. For manufacturers, they recommend blending proteins deliberately, adjusting processing and improving the structure of the products.
Limits of the study
- Digestion was simulated in the lab, not measured in humans or animals. The authors stress that lab models don't fully replicate digestion. The method used, they say, has agreed well with measurements in living organisms, though.
- Only five products from the UK based on soy, wheat and pea were tested. Mycoprotein, faba bean or rice protein were not included.
- The DIAAS refers to the strict reference pattern for young children. For adults, the values would be higher. The study doesn't report them.
- Some numbers in the study text differ slightly from the tables. We use the table values.
Frequently asked questions
Do plant-based chicken alternatives have enough protein?
A bit less than chicken: 21.5 to 32.2 g per 100 g compared with 26.0 to 33.1 g for cooked chicken. In the study, however, the quality was much lower, with a DIAAS of 52 to 65 compared with 151 to 162 for chicken.
Does soy help in meat substitutes?
Not enough in this study. Even the three products with soy stayed below a DIAAS of 75. In each of them, methionine and cysteine were limiting.
How can I upgrade a meat substitute?
By combining it with protein sources that supply the missing amino acids. The study authors also suggest that manufacturers blend proteins deliberately and adjust processing.
How does your meal score?
Open the calculatorSources
- Alotaibi, M., Muleya, M., Salter, A., Hoad, C. & Eldeghaidy, S. (2026): Comparison of the protein quality of chicken and plant-based chicken analogues using the INFOGEST in-vitro digestion system. Food Chemistry 520, 149734. doi:10.1016/j.foodchem.2026.149734
- Sharma, K., Zhang, W. & Rawdkuen, S. (2025): Dietary plant-based protein supplements: sources, processing, nutritional value, and health benefits. Foods 14, 3259. doi:10.3390/foods14183259
- FAO (2013): Dietary protein quality evaluation in human nutrition. Report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92, Rome. PDF
You can find values for individual foods and where they come from under Data & sources. How proteinscore calculates is explained under Method.