Proteins are biological macromolecules formed by chains of simpler components linked together, called amino acids.
In our body they are present in all cells and perform many different functions: they have structural and plastic function, are involved in various enzymatic processes, at the level of the immune system, transport, have hormonal and regulatory functions, contractile, homeostatic and energy or reserve.
- Structural proteins are those that, as their name implies, constitute the structure of tissues and organs of our body, giving them strength and elasticity. Example: collagen, keratin (which we find in hair and nails), elastin and many others.
- Proteins with enzymatic functions are the most numerous and serve to accelerate chemical reactions that take place in our body. Most of the enzymes used in our metabolism are proteins.
- Proteins with a defensive function are those produced by the immune system, known as antibodies or immunoglobulins; they intervene to defend our organism against viruses and bacteria.
- Transport proteins have the function of transporting different substances from one point to another of our body. For example, hemoglobin transports oxygen in the blood.
- Regulatory proteins are used to regulate and control cellular processes. Some hormones and some compounds present in the digestive juices are proteins.
- Contractile proteins are essential to allow the movements of the body, in particular that of the muscles, including the heart, but also that of the eyelashes, for example. Our muscles contract and expand through the action of the two contractile proteins actin and myosin,
- Proteins with a homeostatic function serve to keep the internal pH of the body stable, functioning in some way as “shock absorbers”.
- Proteins with an energy or reserve function are sources for storing amino acids. These proteins can also be used as an energy reserve, providing up to 4 Kcal of energy per gram, but of course it does not make much sense to use proteins for this purpose: carbohydrates and fats are the substances responsible for providing energy. When our body uses proteins as a source of energy it means our diet is not balanced and provides an insufficient quantity of calories.
PROTEINS IN VEGETABLES
Proteins are found in all vegetables. Apart from fruit, which has a modest protein content, and oils (olive or seed), all other foods have a protein content of 15% or more of their calorie content: 15% is exactly the maximum protein content recommended in a healthy diet (this means that out of 100 calories in the diet, 10-15 must come from protein).
To better understand the nutrient content of foods we talk about the “nutritional density” of a food, a very simple concept: it is the amount of a given nutrient expressed per 100 calories.
For protein, we talk about “protein density”. The protein content of a food can be measured in grams of proteins per 100 grams of food (and this is what we usually find in nutritional labels) or as density, that is the quantity of calories deriving from proteins per 100 calories of the food, and it is therefore expressed as a percentage.
Vegetable foods richest in proteins are legumes, including soy and all its derivatives and legume flours: they have an average protein density of about 35%; other foods particularly rich in proteins are those based on gluten (gluten is the protein part of cereals), such as seitan and its derivatives, but also nuts and seeds have a good content, reaching 11% of protein density. All cereals and pseudo cereals are an excellent source of protein, reaching 14%.
But vegetables are also rich in proteins: in this case it should always be used the concept of protein density, not of grams of proteins per 100 of food, as vegetables are mainly made of water and have a low caloric content. In terms of protein density, vegetables contain 15% to 50% protein, averaging 34-35%, as do legumes.
All plant foods (except fruits and oils) contain an equal or greater proportion of protein than our bodies need.
|FOOD||PROTEIN g/100 g||CALORIES x 100 g|
|nutritional yeast flakes||46,8||266|
|Dry cannellini beans||23,4||279|
|dried sweet almonds||22||603|
|dried chick peas||20,9||316|
|dried borlotti beans||20,2||291|
|cooked green branchy broccoli||15||105|
|Whole wheat rusks||14,2||379|