Proteins are essential macronutrients, which we find in foods of animal origin such as meat, fish, eggs or dairy products and also in foods of vegetable origin such as legumes, cereals, nuts or oilseeds. The term "essential" indicates the fact that they must necessarily be taken with the diet, through the intake of a wide variety of foods, since our organism is not able to synthesize them themselves and their deficiency could cause malnutrition and disease.
They are vital because they perform different biological functions, not only a structural function (proteins are famous as "building blocks of the body"), but also that of participating in biochemical reactions (enzymes), transporting substances through cell membranes, defending ourselves from aggressions by external agents (antibodies are proteins) or transmitting cellular signals. Neurotransmitters, hormones or hemoglobin, which carries oxygen into our body, are all proteins!
Up to this point there is no difference between animal and vegetable proteins because we are able to obtain our cellular proteins from both plant and animal sources.
What is the difference between plant and animal proteins?
From a chemical point of view, proteins are complex molecules, consisting of individual elements called amino acids, which are characterized by the presence of nitrogen, responsible for the bond between one amino acid and another. The amino acids available to form a protein are a total of 20, which combined in different ways, form a huge amount of sequences that differentiate proteins and their functions.
The 20 amino acids that make up the structure of our proteins are divided into two groups: "essential" and "non-essential". The essential should be taken with the diet, while non-essential can be synthesized from the essential. In general, the nutritional value of a protein is assessed on the basis of its amino acid profile, which will be complete, if all essential amino acids are present in that protein. An index of the nutritional quality of a protein is its chemical score, which is obtained by comparing the amino acid profile with a reference protein. In addition to the chemical index, another important parameter is bioavailability, that is, the ability of our organism to absorb and use proteins efficiently.
It is now that the differences between animal and plant proteins become important.
When we talk about animal vs plant proteins, we often refer in particular to nutritional value and content in essential amino acids. Until recently, animal proteins were referred to as "noble proteins", while plant proteins were defined as "poor" from a nutritional point of view. This is because animal proteins contain the 9 essential amino acids, while vegetable proteins are often deficient in some essential amino acids. Legumes, for example, are deficient in certain sulfide amino acids such as cysteine and methionine, which are called “limiting amino acids”. Most vegetable proteins contained in legumes, cereals and dried fruits have one or more limiting amino acids.
Is it true that vegetable proteins are “poor”?
Many people still believe that choosing proteins of plant origin the diet may be deficient from a nutritional point of view: but how is it possible that there are people who have been following a 100% plant-based diet for years without incurring malnutrition and disease?
In truth, through vegetable proteins we can optimally cover our needs, in terms of quality and quantity, as demonstrated by several scientific studies.
The first studies were conducted as early as the 1970s and showed that a diet based on different varieties of cereals and legumes was perfectly capable of ensuring the maintenance of the positive nitrogen balance and that the addition of animal proteins to this diet did not appear to add any advantage.
All the most recent scientific work carried out on lacto-ovo-vegetarian and vegan diets now considers the need to combine proteins to be obsolete, to the point that this practice is often no longer even mentioned by associations operating in the field of human nutrition. Also, in the official position of the American Dietetic Association it reads "Given that plant foods are consumed in a varied way and that energy needs are met, vegetable proteins are perfectly able to meet nutritional needs. Research indicates that a variety of plant foods taken during the day are able to provide all essential amino acids and ensure nitrogen intake and use in healthy adults, indicating that complementary proteins do not necessarily need to be consumed within the same meal."
The secret is therefore the variety, that is, the presence, in the diet, of a wide variety of foods. Legumes, for example, have a good protein content, but are deficient in some essential amino acids. For this reason they cannot be the only source of protein in our diet. The solution lies in consuming, during the day, other foods rich in essential amino acids of which legumes are lacking, such as the different types of cereals (not only the best known rice or wheat), dried fruits, shoots, oilseeds.
This would always be true, both in case of omnivorous diet, and in case of vegan or lacto-ovo-vegetarian diet.
Often, however, this is not the case, and, indeed, often, that it follows an omnivorous diet consumes a very low variety of foods.
What if plant proteins are better than animal proteins?
Not only that, but there are some benefits of consuming plant proteins vs animal proteins; animal derivatives such as eggs, meat, or dairy products are a good source of protein, but at the same time they contain saturated fats and cholesterol, unlike plant foods, which are absolutely lacking. For this reason, vegetable proteins are much healthier of animal proteins and can be found in various types of foods, which it is important to learn to know to balance our diet.
There is only one thing that needs to be clarified talking about animal proteins vs plant proteins: the bioavailability.
Foods of plant origin are rich in fiber and other elements that interfere with absorption and digestion and are called "anti-nutritional". Soybeans, for example, contain enzyme inhibitors that make their proteins not-assimilable, so much so that you do not use to eat it as you do with other legumes simply boiled after being soaked, but it is fermented giving rise to various foods such as tempeh, fermented tofu or tamari. Fermentation is a strategy that allows to reduce the anti-nutritional factors of some vegetable foods, makes them more digestible and makes proteins more bioavailable.
Legumes, in general, contain a small part of anti-nutritional factors, but just soak them and cook them completely to cancel out their effect. This also applies to oilseeds and nuts, which can be soaked to increase nutrient availability.
Let's end with one last tip dedicated to athletes.
You know very well how important proteins are for maintaining muscle mass and for post-exercise recovery. In particular, branched chain amino acids, BCAA (leucine, isoleucine and valine) are responsible for muscle reconstruction after intense exercise and therefore indispensable for athletes.
A varied, plant-based diet can ensure a complete protein intake even when we want to focus on fast muscle recovery. BCAAs are found in good quantities in legumes and cereals and we can also take them through powders based on vegan protein mixes, low in fiber for greater bioavailability.
About protein powders there are also some differences considering plant vs animal protein powders, but the most important difference for us, who care about the health of the planet, is the lower environmental impact of plant proteins vs animal proteins, and a total respect for animals.
Author: Francesca Deriu, Nutritionist at Minutro
Clark, H.E., Malzer, J.L., Onderka, H.M., Howe, J.M. and Moon, W. (1973). 'Nitrogen balances of adult human subjects fed combinations of wheat, beans, corn, milk, and rice', Am. J. Clin. Nutr., 26, 702-706.
Edwards, C.H., Booker, L.K., Rumph, C.H., Wright, W.G. and Ganapathy, S.N. (1971). 'Utilisation of wheat by adult man; nitrogen metabolism, plasma amino acids and lipids', Am. J. Clin. Nutr., 24, 181-193.
Lee, C., Howe, J.M., Carlson, K. and Clark, H.E. (1971). 'Nitrogen retention of young men fed rice with or without supplementary chicken', Am. J. Clin. Nutr., 24, 318-323
ADA Reports. Posizione dell'American Dietetic Association e dei Dietitians of Canada: Diete Vegetariane. J Am Diet Assoc. 2003;103: 748-765