Most citizens are aware that proteins are an essential macronutrient for the body. What is no longer so clear is that quality protein sources are so easily identified. It is common to identify them with meat and fish, if anything, also with eggs and dairy products. However, there are many fewer who expand this group of macronutrients to foods rich in protein, but of plant origin, such as legumes, nuts and cereals.
This is what proteins are like
Proteins “are chains formed by the union of small molecules called amino acids. There are 20 amino acids, of which 9 are essential. This means that humans cannot synthesize them and must ingest them from the diet,” explains Begoña García Herreros, member of the Spanish Academy of Nutrition and Dietetics.
Animal vs. vegetable protein: differences
The main difference between animal protein sources and those of plant origin is that “animal protein generally has a Greater digestibility than vegetable protein. In addition, its content and proportion of amino acids is usually higher than that of foods of plant origin.”
Recommended daily amount of protein
One of the questions that most frequently arises in consultations with dietitians-nutritionists is ‘how much protein should I consume?’ The answer is that the Ideal amount of protein should be adapted to the characteristics of each persontaking into account their caloric needs, as well as physical constitution, age or type of physical exercise, among others. Under normal health conditions, the recommended daily intake should be placed between 10-20% of the total daily caloric intake, although It could reach up to 35%.
The expert translates these estimates into concrete figures with an easy-to-view example. “Taking into account that proteins provide approximately 4 kilocalories per gram, an adult woman with light physical activity who weighs 60 kilos and who must ingest approximately 2,000 kilocalories per day, should consume approximately 60 grams of protein per day. That is, about 240 kilocalories (12% of total intake). How do you get them?
The expert points out that the Mediterranean diet provides a sufficiently wide range of foods to supply us with proteins in a varied and healthy way. The quantity and distribution in the weekly menu will be personalized and adapted to the needs and tastes of each individual.
Quality protein vs amino acid pool
The old concept ‘quality protein’ referred to the contribution and proportion of amino acids and the digestibility of the protein itself. It was understood that a quality protein is one that provides all the amino acids and is easy to digest. This idea little by little gives way to the concept of ‘amino acid pool’.
As if it were a construction game, our body is capable of forming the proteins it needs from a variety of amino acids circulating in the blood. These proteins are not only going to form muscle tissues. They will also form our hormones (serotonin, thyroxine, adrenaline, melatonin, among others) or our enzymes.
Every time we eat, we ingest different blocks (amino acids) that our body will use to build the houses and castles that we need for the game (that is, the different protein structures that our body needs). We can’t know if the amino acids in Tuesday’s steak will exactly go to build biceps or help form melatonin to sleep well at night.
This set of amino acids is known as amino acid groupwhich are all the amino acids that an adult ingests throughout 24 hours at different meals of the day. It is not necessary to ingest all of these amino acids in the same meal, but we can complete that ‘castle’ of amino acids throughout the day. The most paradigmatic example is that of legumes (low in methionine) and cereals (low in lysine): previously it was said that legumes had to be accompanied by rice or bread in the same meal to complete all the amino acids. It is now known that compensating at breakfast (for example, with toast or oatmeal porridge) or at dinner (pasta salad) is enough.
Main protein sources
Proteins of animal origin
Dairy, fish, shellfish and eggs, meats,
Plant-based proteins
Legumes (lentils, chickpeas, beans, peas, soy, lupins,…), nuts, cereals and their derivatives.
Protein functions
To the question of what proteins are for, the expert responds with a list of functions:
- Structural function. They support tissues, such as collagen.
- enzymatic function. They regulate our metabolism by participating, activating or stopping all the chemical reactions that take place in our body.
- Transport. They transport very important molecules, such as hemoglobin, which is the protein responsible for transporting oxygen to all our cells.
- Immune function. Many proteins are within our defensive cells (antibodies).
- motor function. It is responsible for allowing the muscular contraction of our heart and the rest of the muscles, for example.
- Energy source. Proteins provide 4 kilocalories for each gram of protein. However, as an energy substrate they are less efficient than carbohydrates or fats. “In fact, when we consume an excess of our proteins for energy, it is a key indicator of malnutrition,” he warns.
Risks of excessive protein consumption
Eating excess protein continuously over time can pose significant risks to vital organs, especially the kidneys and liver, as well as other structures, such as bones.
- kidneys. “Proteins contain nitrogen that, to eliminate it, must be converted into urea, which could overload kidney function. ”.
- liver. «This organ is one of those in charge of protein synthesis, it is our laboratory of protein regeneration, which is forced when protein metabolism is high.»
- Bone. “It could also lead to the appearance of imbalances in bone mineral balance, due to the loss of calcium in the urine.”
Protein and weight control
Diets with adequate protein intake help in weight control if they are varied and well designed. This is explained by its satiating role, since its digestion is slower, and its thermogenic effect, that is, metabolizing proteins uses more energy than other nutrients, such as fats or carbohydrates. However, that does not mean eating proteins will make you lose weight.
When asked if protein makes you fat, or if you can lose weight with protein, the key is the source and frequency of consumption. “If we choose fatty meats, that can translate into an increase in daily calorie intake. But if the proteins come from legumes and cereals, and we accompany them with vegetables, we not only ensure the proteins, but we are providing other essential nutrients, such as satiating fiber,” points out the dietician-nutritionist.
Sarcopenia and the role of protein intake
When a person loses muscle mass, either due to age, lack of physical activity, dietary deficits or illness, a physiological state called sarcopenia or pathological loss of muscle mass appears. In these cases, a complete assessment of the nutritional status will be necessary to adjust the contribution of proteins, carbohydrates and fats in the diet. Also to assess the need for supplements, always under health supervision, for example, that of the dietician-nutritionist in environments, generally hospital and as members of multidisciplinary teams. In these cases, again, the nutritional diagnosis will guide the recommendation of supplementation and daily protein intake. “Depending on the causes of this sarcopenia, the nutritional recommendation will go one way or another,” warns García Herreros.
Which protein foods are most sustainable?
A sustainable source of protein is “one whose production, distribution and consumption makes efficient use of natural resources.” Land use, greenhouse gas emissions, water use or the preservation of biodiversity are key determinants of the sustainability of food systems. In order, vacuum-packed meats and lamb and cheeses are at the top of the protein sources with the greatest environmental impact, followed by pork and poultry, with the most effective, in terms of sustainability, being legumes and cereals. On the other hand, García Herreros takes a stand in favor of local products, as it reduces the impact that transportation causes, which is very high in protein foods produced miles away.
“We are a very rich country in agricultural and livestock production. The food industry in Spain is excellent. In addition, it is increasingly easier to find local, ecological products that respect the environment and animal welfare. We, the consumers, have the key to make everything work well,” he concludes.
The ALDI Council
Do you want to eat healthy? Try to reduce the consumption of protein foods of animal origin and increase those that provide traditional plant proteins (legumes, nuts, cereals, etc.) and those that are new to our diet (tofu, seitan, tempeh, etc. .). .).
Begoña García. Engineer in Agri-Food Industry, graduated in Human Nutrition and master’s degree in Nutrition and Health. She is a member of the Spanish Academy of Nutrition and Dietetics and currently works as a secondary school teacher.
