Vegetable proteins: functions, benefits and main sources

Vegetable proteins. Introduction

In recent years the people who follow vegan and vegetarian diets they are constantly increasing, either for ethical reasons or for the health benefits of regular consumption of vegetable proteins. For this reason, the dietetics market is changing to meet the demands of this type of consumer. From this point of view, vegetable proteins are increasingly present both on the tables of the town and in the gym where they are used as a supplement.

Proteins: function and structure

Proteins are large molecules widespread in both the animal and plant world. The proteins in our organism play multiple roles: they have a plastic function, that is, of tissue construction and repair, they intervene in the manufacture of enzymes, hormones and antibodies. Proteins are composed of amino acids, those present in nature are 20. Of these 10 are considered essential for humans, as our body is unable to synthesize them so they must necessarily be taken with the diet.

Recommended protein requirement

Together with carbohydrates and lipids, proteins are i macronutrients they provide energy to our body. The LARN indicate the amount of protein to be taken in an adult in good health 0,8-1 gr / kg of ideal body weight per day. This value varies in pregnant and lactating women, children and the elderly.

Plant protein sources


The forgotten greats of modern cuisine but not traditional ones represent the most recommendable vegetable protein sources. Lentils, broad beans, cicerchie, chickpeas, yellow soybeans, beans, lupins, etc., have a balanced content in the various essential nutrients for the body. Legumes give a greater sense of satiety than protein sources of animal origin, thanks to the presence of complex carbohydrates and fiber. The carbohydrates of legumes, being slowly absorbed by the intestine, keep the blood sugar levels stable. The average protein content of 100g of dried legumes is equal to an average protein content of 100g of raw meat. This protein content decreases in fresh legumes. On the other hand, legumes have cysteine ​​and methionine as limiting amino acids, amino acids that are instead present in good quantities in cereals, which in turn are free of lysine and tryptophan. This is why legume and grain combinations are great for providing a complete amino acid pool. The only legume that is complete is soy.


Baked goods typically provide only small amounts of protein which contribute to the daily protein quota given their consumption throughout the day. In addition to the traditional bread, pasta and rice, we must not forget barley, spelled, oats, millet and rye. It is preferable to consume whole grains to take advantage of all the advantages: they have, in fact, lower energy density than refined cereals. Furthermore, most of the vitamins and minerals are contained in the outermost part of the grain, after refining the wheat flour, for example only 20% of the vitamin B1 that was present at the beginning remains. Among the most protein cereals there are the vein (16,4g of protein), and the rye (16g), and the farro (15,1g).


They are those "grains" that are often used in the kitchen in a similar way to cereals, but derive from other plant families. Pseudocereals such as quinoa, buckwheat, amaranth and millet guarantee a good supply of high biological value proteins (12-18%), thus representing a good protein source. They are also rich in vitamins and minerals. They do not contain gluten and can therefore be safely consumed even by those suffering from celiac disease or gluten sensitivity.


Seitan is obtained by working with wheat flour (but also with Kamut or spelled), in such a way as to extract gluten and eliminate starch. A soft, consistent and more protein-concentrated dough is obtained, due to the high gluten content. With a delicate flavor it has a meat-like appearance, but has a softer consistency than the latter. The vegetable proteins in fresh seitan amount to 18 grams per 100 grams of product. It is also low in carbohydrates, low in fat and contains no cholesterol. Seitan is a food not suitable for celiacs.

Nuts and seeds

Nuts (walnuts, hazelnuts, almonds, cashews, pine nuts and pistachios) and oilseeds (pumpkin, hemp, sunflower, flax, chia and sesame seeds) are a good source of protein, but also of good fats and minerals, fiber and antioxidants. The protein intake of pumpkin seeds is quite high: 30,2 grams in 100 grams of product. In particular, the small and precious hemp seeds contain all the essential amino acids and 25 grams of protein in 100 grams of product. Nuts and seeds can represent a protein supplement to be consumed to support main meals, they can be chopped and added to salads, sauces, gravies and other culinary preparations as well as being a practical and convenient alternative to take and eat as a snack.


Tofu is considered soy cheese, due to its appearance and preparation similar to the classic cheese. Its flavor is quite neutral, for this reason it lends itself to being used for many dishes. In addition to presenting a high protein content (8-10g per 100g), the tofu is rich of mineral salts such as iron and magnesium. It is a valid substitute for cheeses, compared to which it contains more proteins, has a high content of unsaturated fats and is cholesterol free. Furthermore, being lactose-free, it can also be inserted without problems in the diet of individuals intolerant to milk


Tempeh is a food based on fermented soybeans, widely used in oriental cuisine with a strong and intense flavor. Excellent source of vegetable protein: 18,5 grams of protein per 100 grams of product. It also has a high content of fiber, vitamins, minerals, phytocompounds and polyunsaturated fatty acids.


Seaweed is an important source of protein with 39,4 grams of protein per 100 grams of dried nori or 16,1 grams of protein per 100 grams of dried wakame seaweed. The good amino acid profile of the spirulina algae, means that this seaweed can represent a valid help to cover the needs of essential amino acids in people who follow a vegetarian or vegan diet.

For further information: Spirulina: What it is and Nutritional Properties

Differences between animal and vegetable proteins

Both animal and plant foods are sources of protein. We often hear of animal and plant proteins as having substantially different chemical and nutritional properties. In reality, all proteins, regardless of their origin, are macromolecules always made up of the same amino acids into which they will be broken down during digestion.

Protein quality

The protein quality it is one of the differences between the two types of proteins. Depending on the greater or lesser presence in their composition of essential amino acids, proteins are divided into ad proteins high biological value (milk, eggs, meats, fish, cheeses), proteins of medium biological value (legumes and cereals) and proteins a low biological value (vegetables). Animal proteins are called nobles because they contain all the essential amino acids. On the other hand, since every single vegetable food is deficient in at least one given amino acid or contains less of it than the animal one, vegetable proteins are incomplete so they cannot be considered valid and noble like the animal ones. However, if we consider that the diet is never based on a single plant food, but various types of them are consumed, a clever combination of them allows us to integrate the deficiencies and provide complete proteins like animal products.

Bioavailability and digestibility

Animal and vegetable proteins also differ in bioavailability e digestibility.

In particular, vegetable proteins are less digestible of those animals. This means that those who follow a vegetarian diet must increase their protein intake by 5-10% compared to that recommended for the general population. However, as most people consume proteins from a variety of sources, their quality and digestibility usually aren't a problem.

Recently FAO / WHO have introduced a new parameter the PDCAAS (protein digestibility corrected aminoacid score, corrected amino acid value for protein digestibility) as an ideal system for classifying protein quality, which takes into account both the amino acid content and the digestibility of proteins. Its maximum value is 1,0 (proteins with this value are considered ideal and "COMPLETE" for humans).

What are vegetable proteins used for


An increased consumption of fruits, vegetables, whole grains, legumes, nuts and seeds and various soy products can lead to countless health benefits.

Plant-based foods as opposed to animal foods contain fiber. Of these, the insoluble ones reduce the digestibility of proteins but are important for thebalance of intestinal flora, help regularity and transit, improving intestinal peristalsis andelimination of toxins from the body. Soluble fibers, on the other hand, by binding to water contribute to having a sense of gastric fullness, useful for those who follow low-calorie diets. ¹

By preferring plant foods to animal ones, we do not supply our body with saturated fats and cholesterol, which are notoriously harmful to health, thus decreasing the risk of cardiovascular disease. In particular, soy and its derivatives are very rich in high quality proteins and their introduction into the diet decreases bad cholesterol (LDL) levels, blood pressure risk factors for atherosclerosis. An increased intake of fruit and vegetables can reduce cardiovascular risk also because it brings vitamins, fibers, mineral salts and phytochemicals to the diet. ¹⁻³

Foods rich in vegetable proteins are able to do decrease Insulin-like Growth Factor (IGF1) levels in the blood (a potent mutagenic factor produced by the body), to improve the insulin / glucagon axis and reduce the risk of diabetes mellitus. ²

A high consumption of legumes is also protective for some types of cancer (to the colon, pancreas, prostate). In particular, according to some studies, the consumption of soy and derivatives containing phytoestrogens is useful in preventing hormone-sensitive tumors such as breast cancer. ⁴

Possible contraindications

Using only vegetable proteins may increase the risk of some nutritional deficiencies. The micronutrients to which particular attention must be paid are vitamin B12 and D, calcium and long-chain fatty acids (omega 3). In some cases, even the iron and zinc content can cause concern, due to the limited bioavailability of these minerals. The best solution is therefore a balanced diet. A well-planned vegetarian diet that includes fortified foods can be nutritionally adequate for adults and children. ⁵


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Nutrition concerns and health effects of vegetarian diets

Winston John Craig 1

² Review Curr Diab Rep. 2018 Sep 18;18(11):101

Vegetarian Diets and the Risk of Diabetes

Melissa D Olfert 1, Rachel A Wattick 2

³ Review Crit RevFood SciNutr.2017  Jun13;57(9):1950-1962

Dietary fruits and vegetables and cardiovascular deseases risk

Eman  M Alissa 1 Gordon A Ferns  2

⁴ Cancer Med. 2018 May;7(5):2131-2144. Epub 2018 Mar 23.

Intake of bean fiber, beans, and grains and reduced risk of hormone receptor-negative breast cancer: the San Francisco Bay Area Breast Cancer Study

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⁵ Am J Clin Nutr 2009 May;89(5):1627S-1633S Epub 2009 Mar 11.

Health effects of vegan diets

Winston J Craig 1

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