Is soya protein healthy? What are its properties?
Soya protein is derived from the seeds of the common soya bean (Glycine max), a legume that has been used in Asian cuisine for centuries. As early as 965, a Chinese source described tofu as an inexpensive substitute for mutton, which less affluent people could afford. Today, soya is an ingredient in traditional dishes, meat substitutes and protein supplements. Its nutritional value depends, amongst other things, on the type of product, the method of processing and the protein content.
What is soya protein? Nutritional value and amino acid composition of soya protein Properties of soya protein FAQ – frequently asked questions about soya protein
What is soya protein?
Soya protein is a mixture of various proteins found in soya beans, primarily glycinin and beta-conglycinin. In the food industry, it is usually obtained from defatted soya flakes or soya flour by separating out some of the fat and non-protein components. The degree of purification determines the protein content and the properties of the final product.
Soya flour usually contains around 40–55 per cent protein, depending on whether it has been defatted. Soya protein concentrate usually provides around 65–70 per cent protein on a dry matter basis. Isolate is more highly purified and contains at least around 90 per cent protein on a dry matter basis, which is why it is often used in protein powders. The figures on the finished product’s label may be slightly lower due to the presence of water, flavourings or other additives.
Textured soya protein is a separate category, produced through a process that gives it a fibrous structure. It is sold, amongst other forms, as granules, cubes or patties, which, once rehydrated, are used in savoury dishes.
Nutritional value and amino acid composition of soya protein
Soya protein provides all nine essential amino acids, which the body cannot produce in sufficient quantities on its own. These include, amongst others, leucine, lysine, threonine and tryptophan. Compared with many other plant proteins, soya stands out for its favourable lysine content, whilst it contains relatively fewer sulphur-containing amino acids, particularly methionine.
The quality of protein is determined not only by its amino acid profile, but also by its digestibility and bioavailability following digestion. Unprocessed seeds contain, amongst other things, trypsin inhibitors – substances that limit the activity of enzymes that break down proteins. Appropriate heat treatment reduces their activity, whilst processing the raw material can affect the digestibility of the resulting protein. For this reason, protein quality indicators vary between whole seeds, tofu and protein isolate.
The amount of protein also depends on the water content of the food. 100 g of tofu often contains around 8–15 g of protein, 100 g of tempeh around 18–21 g, and 100 ml of soya drink usually around 3 g. Individual brands can vary significantly in composition, particularly in the case of tofu and drinks fortified with additional ingredients. Supplements based on soya protein isolate usually contain around 80 g of protein per 100 g of powder, which corresponds to approximately 24 g of protein per serving.
The four amino acids present in the highest amounts in soya protein isolate
(g per 100 g of pure protein).
Properties of soya protein
Protein plays a role in the formation and regeneration of tissues, as well as in the production of enzymes and transport proteins. According to health claims authorised in the European Union, it contributes to the growth and maintenance of muscle mass, and also helps to maintain healthy bones. These are the properties of protein as a nutrient, regardless of its origin, and are not effects specific to soya. Such claims may be included on labels and in product information where protein provides at least 12 per cent of the energy value, which is a condition for using the term "source of protein" in accordance with EU regulations.
Soya protein is used in the diets of physically active people, including as a substitute for dairy proteins. Interventional studies analyse its use in combination with resistance training, but the results obtained depend on the dose, total protein intake, type of training and duration of observation. There is no basis for attributing an advantage to any particular soya-based product over other protein sources.
"Soya protein provides all nine essential amino acids and can be a valuable source of protein in both plant-based and mixed diets. However, its quality depends on the processing method, digestibility and composition of the specific product. In practice, it is worth comparing the protein content per serving, rather than assuming that isolate, tofu and soya drink have the same nutritional value. ” Anna Zięba – Dietitian
FAQ – frequently asked questions about soya protein
Is soya protein healthy?
Soya protein can be a valuable part of a varied diet. It provides all the essential amino acids, and protein, as a nutrient, helps maintain muscle mass and healthy bones. However, the nutritional value of a particular product also depends on its other ingredients and how it has been processed.
Is soya protein a complete protein?
Yes. Soya protein contains all nine essential amino acids, including leucine, lysine and tryptophan. However, it has a slightly different amino acid profile to animal proteins, including a relatively lower methionine content.
Does soya protein help build muscle?
Soya protein provides the amino acids needed for muscle growth and recovery. It can be included in the diet of those doing strength training, but the effects also depend on the type of training, total protein intake and recovery. It has not been shown that any particular soya product is more effective than other sources of protein.
Which is better: soya protein or whey protein?
Both provide essential amino acids, but they differ in their proportions and properties. Soya protein is a plant-based option, whilst whey protein comes from milk. The choice depends primarily on your diet, how well you tolerate the products, and the composition of the specific supplement.
How much protein do tofu, tempeh and soya drink contain?
According to the figures given in the article, 100 g of tofu usually contains around 8–15 g of protein, and 100 g of tempeh around 18–21 g. Soya drink provides an average of around 3 g of protein per 100 ml. The exact amounts depend on the product and the manufacturer.
How does soya protein isolate differ from concentrate?
Isolate is a more purified form and contains at least around 90 per cent protein on a dry matter basis. Concentrate usually provides around 65–70 per cent protein on a dry matter basis. Ready-made supplements may have a lower protein content due to added ingredients.
Does soya protein lower cholesterol?
A meta-analysis of 46 studies published in 2019 showed that the consumption of soya protein was associated with a slight reduction in LDL cholesterol and total cholesterol levels in adults. However, this does not mean that soya supplements can replace treatment for lipid disorders.
Does soya protein lower testosterone levels in men?
A meta-analysis of clinical trials published in 2021 found no significant effect of soya consumption or soya isoflavones on testosterone levels or other reproductive hormones analysed in men. The available data therefore do not support the popular claim that regular consumption of soya lowers testosterone.
Is soya protein suitable for vegans and vegetarians?
Yes. Soya protein is plant-based and can be an important source of amino acids in a vegan or vegetarian diet. You can choose between tofu, tempeh, soya granules and protein supplements, depending on your needs and preferences.
What should you look out for when buying soya protein?
The most important factors are the amount of protein per 100 g and per serving, the type of raw material, and the full list of ingredients. For example, 30 g of a supplement containing 80% protein provides approximately 24 g of protein. People with a soya allergy should avoid products containing soya protein.
Sources:
van den Berg, L. A., Mes, J. J., Mensink, M., & Wanders, A. J. (2022). Protein quality of soy and the effect of processing: A quantitative review. Frontiers in nutrition, 9, 1004754. https://doi.org/10.3389/fnut.2022.1004754 Blanco Mejia, S., Messina, M., Li, S. S., Viguiliouk, E., Chiavaroli, L., Khan, T. A., Srichaikul, K., Mirrahimi, A., Sievenpiper, J. L., Kris-Etherton, P., & Jenkins, D. J. A. (2019). A Meta-Analysis of 46 Studies Identified by the FDA Demonstrates that Soy Protein Decreases Circulating LDL and Total Cholesterol Concentrations in Adults. The Journal of nutrition, 149(6), 968–981. https://doi.org/10.1093/jn/nxz020 Reed, K. E., Camargo, J., Hamilton-Reeves, J., Kurzer, M., & Messina, M. (2021). Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies. Reproductive toxicology (Elmsford, N.Y.), 100, 60–67. https://doi.org/10.1016/j.reprotox.2020.12.019
ADDED:
22/10/2026
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