Besides being a practical snack, nuts are also recommended as they provide energy, fibre and many macro and micronutrients that are essential for the health and well-being of your body.
Among the nutrients contained in every portion of nuts, protein represent one of the main nutrients.
Proteins are the most versatile class of biological molecules. The basis of the protein structure are the amino acids, i.e. organic compounds containing a carboxylic group (COOH) and an amino group (NH2), which differ from each other by a more or less complex residual group. The simplest structure is that of glycine, whose residual group corresponds to a hydrogen atom. From the nutritional point of view, amino acids are divided into essential amino acids, i.e. those that we must necessarily introduce with food because our body is not able to produce them independently, and into non-essential amino acids. All the body's proteins are made from 23 amino acids. Among these there are 8 essential amino acids in adults (lysine, tryptophan, threonine, methionine, phenylalanine, leucine, isoleucine and valine) and 10 in children (plus histidine and arginine).
Proteins are thus molecules, with complex structures, made of amino acid chains, held together by peptide bonds, which perform many functions within the body: enzymatic, structural (collagen and keratin), contractile (actin and muscle myosin), transport (hemoglobin), signal (hormones) and many others.
The total protein content of some types of dried fruit is relatively high, making it a good source of vegetable protein:
Despite the protein content of nuts being rather high, the biological value of this protein is not as high. The biological value is the unit of measurement used to assess the quality of the proteins we consume in our diet and is mainly based on their content of essential amino acids. Proteins of animal origin, especially eggs (containing about 13 g of protein per 100g), have a high biological value while vegetable proteins generally lack one or more essential amino acids.
Several studies have evaluated the amino acid composition of nuts and the result was that the amino acid content changes depending on the type of nuts under examination as well as of the cultivar. In an analysis carried out in 2006 a comparison was made between the protein content of different types of nuts with egg protein, which is the standard food with the highest biological value: the result was that, in general and with the due differences between one type and another, the amino acid profile of nuts is poor in threonine, lysine, methionine and in some types also of other amino acids.
Obviously, there is no need to despair: the balanced intake of nuts has considerable advantages for the body thanks to their content in fibre, but also in unsaturated fatty acids, omega-6 and omega-3, which contribute to the normalisation of cholesterol levels in the blood, and numerous minerals and vitamins contained in it, in particular vitamin E contributing to the protection of cells from oxidative stress.
A further interesting aspect concerns the fact that the intake of plant protein has been associated with a low cardiovascular risk compared to animal protein intake. The explanation could lie in the relationship between the amino acids lysine and arginine contained in plant proteins. Plant proteins, like nuts proteins, are generally rich in arginine and poor in lysine, while the opposite is true for animal proteins. The risk of developing diseases related to the cardiovascular system (hypercholesterolemia and atherosclerosis) is higher when eating mainly foods that have a high lysine:arginine ratio. Moreover, preferring plant proteins over animal proteins also seems to have positive effects on the regulation of glycaemia and insulinemia.
The most important thing, especially for those on a vegan diet, is to be able to combine food well so as to assume all the essential amino acids from different vegetable sources and integrate their diet in a balanced way: for example, you can create unique dishes by combining nuts with legumes, cereals and/or other vegetables.
On the other hand, for those on a vegetarian diet the situation is easier because for them it is possible to take eggs and dairy products in order to provide noble proteins, always remembering that in a balanced diet proteins must represent 15-20% of the nutrients.
Sources:
Gemma Brufau, Josep Boatella and Magda Rafecas; Nuts: source of energy and macronutrients; British Journal of Nutrition (2006), 96, Suppl. 2, S24–S28.
Emilio Ros; Health Benefits of Nut Consumption; Nutrients. 2010 Jul; 2(7): 652–682.
