Proteins: Everything You Need To Know So You Don’t Miss Out

It is a widespread belief that plant foods are devoid of protein, or that it is a challenge to obtain your necessary daily amount from a plant diet. Nothing is further from reality. Today it is widely recognized that a plant-based diet can provide enough protein, as long as there is not a total calorie deficit. Still, it is wise to be familiar with the basic dietary recommendations in order to choose the healthiest options. In this article we will delve into amino acids from a more vegan perspective.

The human body is made up of one sixth of proteins. These nitrogenous substances provide it with structure and energy, and allow it to carry out almost all vital processes, such as digestion, muscle contraction, clotting, oxygen transport, and the formation of hormones, neurotransmitters, and antibodies.

It is understandable that in the 19th century proteins were named after the Greek word “proteicos” (fundamental, main). They constitute one of the three large groups of macronutrients, along with carbohydrates and fats. Its sufficient contribution in terms of quantity and quality is essential to achieve a balanced diet.

Three major groups of amino acids

Proteins are made up of twenty-two different types of amino acids, molecules that combine to form each protein with its own sequence. Although plants are capable of producing all the amino acids they need to live, animals and humans must obtain some of them from food. According to this characteristic, amino acids are classified into two groups:

• Not essential. They are amino acids that the body can create by itself, generally from carbohydrate metabolites, although it requires a supply of nitrogen that can only come from other amino acids in the diet. There are thirteen: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, pyrrolysine, proline, selenocysteine, serine and tyrosine.
• Essential They are the amino acids that our body cannot produce, or at least not in sufficient quantities to maintain health, so they must be obtained through food. They are nine: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Histidine can be included in one group or another. In any case, it is essential for lactating babies who have not yet developed an intestinal microbiota capable of producing it.
• Semi-essentials. In addition, some non-essential amino acids can be considered as such in certain situations: arginine during growth or convalescence; cysteine ​​and tyrosine for preterm infants; and glutamine, the most abundant amino acid, in situations of greater protein turnover.

Amino acid derivatives

There are substances that are not strictly amino acids, but derived molecules, but they have important functions in the body.

• Taurine. It is obtained from the ingestion of meat and fish or from its synthesis in the liver from the cysteine ​​and methionine provided by food, also by vegetables. Its natural presentation (not as a synthetic ingredient in energy drinks) appears to protect against diabetes and cardiovascular disease, and promotes the immune response. It is therefore advisable to eat appropriate amounts of vegetable proteins from which the body will synthesize it. Its high content in human milk is one more reason in favor of breastfeeding, especially for premature infants.
• Carnitine, choline and others. Other amino acid derivatives such as carnitine, choline, cysteine ​​and glycine are also essential for newborns.

The functions of proteins

If we need to get enough essential amino acids from food, it is so that different kinds of proteins can be formed. These proteins not only determine the shape and structure of cells, but also direct almost all vital processes.

We have proteins for cells to defend themselves from external agents, proteins to repair damage, to control and regulate functions … All of them carry out their missions by selectively coupling to the appropriate molecules.

• Structural. Some constitute cellular structures, that is, tissues. They confer elasticity and resistance to organs and tissues. For example, collagen in connective tissue or keratin in the skin.
• Hormonal. Some important hormones are also protein in nature, such as insulin, which regulates glucose levels, growth hormones or calcitonin, which regulates calcium metabolism.
• Regulatory. There are proteins that regulate the expression of certain genes or cell division.
• Homeostatics. Others are responsible for maintaining the fluid balance or the pH of the internal environment.
• Defensive. Immunoglobulins act as defensive antibodies against viruses and bacteria.
• Conveyors. Hemoglobin, lipoproteins, and cytochromes carry oxygen, lipids, and electrons, respectively.

Keep your balance

The loss of amino acids from the body mainly due to its oxidation, conversion into other substances, urinary excretion products of their metabolism (urea, creatinine and uric acid), loss faeces and replacement in tissues.

The obtaining of proteins must be kept in balance with these losses. For this reason, the daily intake of nitrogen and essential amino acids in adequate quantity and quality is essential.

Insufficient protein intake can lead to loss of muscle mass and impaired cognitive and immune system, or even severe malnutrition.
Without going over. On the other hand, excessive protein consumption can cause bone demineralization (especially if fruits and vegetables are not consumed) and liver and kidney disorders.

Get proteins with high biological value

A protein is considered to be of high quality or biological value when it contains the nine essential amino acids in sufficient quantities for the proper functioning of the body. Proteins that do not meet this requirement are considered incomplete or of low biological value. In other words, the biological value of a protein is greater the more its composition resembles the proportion of amino acids in the human body.

The vegetable proteins with the highest biological value are those of soybeans, followed by chickpeas, peas, quinoa, buckwheat and pistachios. The rest of legumes have lower levels of tryptophan and methionine (they are considered their limiting amino acids), while the other cereals, nuts and seeds have low levels of lysine, isoleucine or threonine. Vegetables tend to have low amounts of protein, although some are of considerable biological value.

If we eat portions of all these groups of plant foods throughout the day, and not necessarily in the same meal, their different deficiencies are compensated and we provide the body with the nine essential amino acids without difficulty.

If we eat rice at noon, it would be appropriate to include lentils or chickpeas in the same meal or dinner. Another option would be to combine beans with corn, and garnish your meals with nuts and seeds. Pay special attention to the consumption of legumes and nuts in order to obtain lysine. Soy also provides abundant tryptophan.

How to improve the absorption of amino acids

The digestibility of a protein also determines its quality. Ovalbumin and casein from milk (like maternal milk, the best) are taken as a reference as they are proteins of high biological value and digestibility (they have a PDCAAS or “quality index corrected for digestibility” of 100%).

Most plant proteins have worse digestibility than animal proteins because our digestive system has a harder time breaking the wall of plant cells and breaking down their protein into amino acids. But, once again, soy is an exception and has a PDCAAS of 99%, better than that of beef (92%). To improve the digestibility of legumes, cereals, nuts and seeds, it is useful to soak and cook them. Germinating the seeds is also effective.

What is the recommended daily protein intake?

The general recommendation of protein intake for adults is 0.8 grams per kilo of weight per day, which represents 11-15% of the daily energy obtained from the diet. In vegans and vegetarians this recommendation is maintained, although different authors advise eating up to 1.1 grams per kilo of weight due to the lower digestibility of vegetable proteins.

However, in these diets the quality or biological value of the proteins is more important than the quantity, since multiple studies agree that they do not present an inherent quantitative protein deficit.