Proteins and Amino Acids
General information on proteins
Proteins are polymeric chains formed by the union of numerous amino acids, joined in sequence by bonds called peptides.
In nature there are thousands of proteins, different in structure and function; this variability depends on the number, sequence and type of amino acids, and on the overall three-dimensional structure (conferred by other stabilizing bonds).
Proteins perform many functions that are indispensable to say the least, so much so that the human body contains up to 12-15% of its weight.
The most important functions of proteins are: plastic (make up tissues), bioregulatory (enzymes), hormonal, neurotransmitters, membrane channels, blood transport, immune etc.
Amino acids: what is there to know?
Amino acids are quaternary molecules made up of carbon, hydrogen, oxygen and nitrogen.
There are many types of amino acids, differing in structure and chemical properties.
In addition to constituting proteins, they can be used for energy purposes providing 4 kcal / g. In this regard, some amino acids are used directly by the muscle (they are the branched ones: leucine, isoleucine and valine), while others are converted into glucose by the liver (with the production of residues: ammonium, urea, ketone bodies, etc.).
The human body is capable of synthesizing almost all the amino acids it needs. Only 9 of these must necessarily be introduced with the diet and - for this reason - they are called essential: phenylalanine, isoleucine, histidine, leucine, lysine, methionine, threonine, tryptophan and valine; Arginine, cysteine and tyrosine are also essential for the baby.For further information: Protein Requirement
Protein in the Diet
Proteins and amino acids in food
On the basis of what has been specified so far, it is logical to deduce that the intake of amino acids in the diet is a fundamental aspect for nutritional balance and for maintaining the overall state of health. Fortunately, proteins are widely distributed in foods, albeit with great differences in quantity and so-called "quality".
To tell the truth, there are no proteins that are qualitatively better than others; rather they differ in terms of amino acid content. The more their composition resembles that of human peptides, the greater the guarantee of getting all the essential amino acids; this degree of similarity is expressed with the criterion of "biological value".
The proteins that contain all the essential amino acids in the right quantities and proportions are called "high biological value" (some call them incorrectly "noble proteins").
Food groups and biological value of proteins
Foods that belong to the I and II fundamental groups of foods contain high biological value proteins: eggs, milk and derivatives, and animal tissues (meat, fish, molluscs, crustaceans, insects).
On the other hand, the products of groups III and IV are characterized by proteins of medium biological value: cereals and legumes (with the exception of soy, which is qualitatively superior). Furthermore, nuts (walnuts, almonds, etc.) also contain the same kind of peptides.
Vegetables and fruit (the VI and VII groups) provide only low biological value proteins. Some algae are an exception, which are rich in proteins of good biological value.
Myths to dispel
Let's start by making a distinction:
- Protein deficiency is an objectively diagnosable condition of malnutrition, which has nothing to do with the muscle catabolism of sports or bodybuilding.
- In 99,9% of cases, those who do not recover physically after a workout or who "do not grow" in the muscle, actually do not suffer from any protein deficiency. The causes could be training management or even nutritional, but often complex and more difficult to dissect.
- Protein deficiency does NOT appear before the medium-long term; avoiding mainly protein foods for a few days (for example in case of gastrointestinal infections, acute gastritis, etc.) does not lead to metabolic protein deficiency.
- Those who do not eat meat and fish and vegetarians do not suffer from protein deficiency, as they consume eggs and / or milk and derivatives. In the case of vegans, the matter is more complicated; by varying the foods a lot, it is almost always possible to reach the needs of all the essential amino acids, but it is necessary to rely on a nutrition expert and avoid doing it yourself. Unfortunately, without the use of food supplements, vegans and raw foodists are still destined for some kind of nutritional deficiency.
- Vegans can also eat separate grains and legumes without running the risk of protein deficiency, as long as both are in the right quantities, in the right proportions and are more or less alternated.
Protein deficiency occurs when the dietary supply of these nutrients is not sufficient to satisfy the body's metabolic demands.
The following factors can be the cause of protein deficiency:
- Insufficient dietary intake of total protein (overall insufficient diet, difficulty in chewing, drug addiction or alcoholism, anorexia nervosa, veganism or raw food not properly managed)
- Insufficient dietary intake of high biological value proteins, or rather, of one or more essential amino acids (same circumstances as above)
- Altered digestion and / or food absorption (anatomical - functional gastric, intestinal, pancreatic diseases, infections and parasites)
- Metabolic complications (e.g. severe birth defects or liver failure)
- Increased physiological or pathological metabolic demand (certain forms of renal failure, pregnancy, sports beyond the limits of normality).
To tell the truth, except for the pathological causes, the protein deficiency is a condition that mainly affects the third and fourth ways. In economically affluent societies, on the other hand, it appears very rarely and can concern the lower income brackets (it mainly affects the elderly), psychiatric pathologies, toxic addictions and alternative food philosophies.
Protein deficiency can cause many complications. However, it is necessary to classify the discomforts and symptoms of minor deficiencies from severe ones. Let's proceed in ascending order.
Mild protein deficiency with mild symptoms and clinical signs
Mild protein deficiency can cause:
- Reduced metabolic efficiency (e.g. ease of bleeding, slow wound healing etc)
- Reduction of corpuscle elements in the blood
- Weight loss (as an effect of muscle reduction)
- Reduction of muscle volumes
- Premature fatigue
- Difficulty concentrating and learning difficulties
- Muscle and / or joint and / or bone soreness
- Glycemic changes
- Greater susceptibility to infections.
Less frequently, the following may also appear:
- Increase in cholesterol, blood sugar and body weight (rather a consequence of replacing high-protein foods with junk ones)
- Anxiety (due to impaired synthesis of neurotransmitters)
- Reduced athletic performance (reduced compensation of training stimulus)
- Sleep disturbances (some speculate that it may be caused by impaired synthesis of tryptophan and serotonin)
- Digestive disorders (proteins allow the natural synthesis of digestive enzymes).
Mild protein deficiency with severe clinical symptoms and signs
- Kwashiorkor or biafra, is a malnutrition syndrome, probably multifactorial and in any case characterized by an insufficiency of proteins in the diet
- Muscle depletion: consists of the self-digestion of muscle proteins to produce energy
- Severe reduction of all protein-based components of the body: nails, hair, skin, enzymes, neurotransmitters, hormones, immunoglobulins, etc. The correlated pathologies are innumerable and the symptomatology equally vast.
How to avoid protein deficiency?
Minimum requirement to avoid protein deficiency
For the average country, avoiding protein deficiency is simple: just follow the recommendations of research institutions that suggest to consume AT LEAST 0,8 g of protein per kilogram of physiological body weight (corresponding to about 12-13% of calories totals). This parameter, absolutely "spannometric", guarantees the state of health for a sedentary adult. However, the minimum requirement can be modified by many subjective variables such as: percentage of lean mass, gender, age, level of physical activity and special or pathological physiological conditions.
Food strategy to avoid protein deficiency
Today, in the West, protein deficiency in healthy people is a more unique than rare occurrence; on the other hand, the excess of proteins is more frequent, which however we will deal with in a separate article.
For those unfamiliar with the Mediterranean Diet (naturally balanced diet), the most suitable system to avoid protein deficiency but also excess is the "flexitarian diet". It is a nutritional regime that proposes to consume only whole / whole foods (fruit with peel, whole grains, sprouted seeds, etc.) or unprocessed (raw or pasteurized milk), with a subjective frequency characterized by flexibility. It allows you to eat daily small quantities of foods of animal origin or a large portion only once a week. The prevalence of foods is of a vegetable nature, but this does not mean that the flexitarian diet is low in protein: legumes, in fact, are excellent sources of peptides.
For vegans we recommend:
- Increase the consumption of all types of legumes (soy, adzuki beans, lentils, etc.), oil seeds (walnuts, almonds, flax, chia, hemp), pseudocereals (buckwheat, amaranth, quinoa, etc.).
- Increase the most protein-rich vegetables: spinach, kale, broccoli, sprouts and mushrooms.
- Optionally, make use of legumes or protein isolates from vegetables: soybeans, peas, chickpeas, broad beans, etc.
Role of proteins in aging
Aging is a physiological, degenerative, progressive and inevitable process of cells, tissues and the whole organism. According to numerous researches, it would be accelerated by free radicals. On the other hand, it is possible that protein deficiency may also play a decisive role.
Insights from researcher Jan van Deursen of the Mayo Clinic revealed that some proteins play a very important and critical role in the aging process. By creating genetically engineered mice predisposed to a specific protein deficiency, Jan van Deursen observed that these degenerated four to five times faster than the normal control group.
This protein (BubR1), which naturally decreases even with physiological aging, is reduced not only in skeletal muscles, but also in the tissues of: heart, brain, spleen, testicles and ovaries. Jan van Deursen argues that this can also happen in humans, increasing the risk of the most common diseases in old age: cataracts, heart dysfunctions, kyphosis of the spine due to muscle atrophy, etc.