Food holds the main portion of nutrition we acquire for our body. Hence consumption of the right amount of them is essential. As the generations passed, the healthy eating habits have reduced which resulted in people being more conscious about their health leading to different kinds of diets.
However, these dietary habits might help in losing weight but at the same time makes the body deficient in essential nutrition. Proteins are the building blocks of life. They are polymers of amino acids linked via alpha peptide bonds. They can be represented as primary, secondary, tertiary, and quaternary structures. But from a nutritional viewpoint, only primary proteins are considered.
Similarly, although many compounds in the body can be chemically defined as amino acids, we are only concerned with the 20 canonical amino acids encoded in DNA, plus 5 others—ornithine, citrulline, γ-aminobutyrate, β-alanine, and taurine—that play quantitatively important roles in the body.
Every cell in the human body consists of protein being a chain of amino acids. The proteins we acquire through diet helps in repairing cells and making new ones. It also contributes hugely to the growth and development of children, teens, and pregnant women.
Protein Absorption From Food
Protein foods are broken down into parts called amino acids during the process of digestion. The human body requires several amino acids in large enough amounts to maintain good health. Once consumed and reaches the digestive sites, the portions of food are broken down with the help of a variety of digestive enzymes acting on it.
We consume proteins, which are digested in the gastrointestinal tract, absorbed as small peptides (di- and tripeptides) and free amino acids, and then used for the resynthesis of proteins in our cells. Additionally, some amino acids are also used for the synthesis of specific (non-protein) products such as nitric oxide, polyamines, creatine, glutathione, nucleotides, glucosamine, hormones, neurotransmitters, and other factors.
Again, such functions are not quantitatively important for most amino acids, and the bulk of amino acid metabolism is directly related to protein turnover (synthesis and degradation). For an individual in nitrogen balance, an amount of protein equal to that of the daily protein (nitrogen) intake is degraded each day with the nitrogen being excreted as urea and ammonia (with limited amounts of creatinine and uric acid).
The carbon skeletons of the amino acids degraded to urea and ammonia are recovered through gluconeogenesis or ketone synthesis, or oxidized to carbon dioxide.
Amino acids required for our body is classified into three groups i.e., Essential Amino Acids, Non-Essential Amino Acids and Conditional Amino Acids.
- Essential amino acids include those that cannot be made by the body and must be supplied by food. They do not be eaten completely within one meal. The balance of these over a whole day is important.
- Non-essential amino acids are made by the body from the essential amino acids or in the normal breakdown of proteins.
- Conditional amino acids are already stored in the body via various amounts of nutrition and are used when the body undergoes any illness and any form of stress. Of the 20 amino acids present in proteins, 9 are considered nutritionally indispensable or essential in adult humans, these include leucine, valine, isoleucine, histidine, lysine, methionine, threonine, tryptophan, and phenylamine.
It is suggested that an adult human must consume 0.8g of protein concerning their body weight, with an extra 10 or 15g recommended for pregnant and lactating women. Requirements are higher for growing children and in some pathologic states also.
The protein content of food varies considerably, but general animal sources tend to be superior in both protein quantity and quality when compared with greens. Meat, eggs, and milk are generally considered excellent sources of proteins. Egg protein is often considered as the ideal or complete protein with which the indispensable amino acid profile of other foodstuffs is compared.
Certain plant-based foods such as legumes like beans, peas, and lentils do contain a considerable amount of proteins. However, most legumes tend to be deficient in methionine. Certain cereals contain protein-rich substances however are low in lysine and tryptophan content.
Thus, the combination of different plant-based foods in dishes such as rice and beans, or peanut butter and bread, results in a complementary effect that raises the protein quality when compared with either of these food types consumed alone.
Therefore, adults can obtain adequate amounts of high-quality protein from a vegetarian or vegan diet. It should be noted, however, that taurine may be required for neonates, and that taurine is only present in animal-based foodstuffs.
The protein quantity in each food item is determined usually by the calculation of total nitrogen content in that food item multiplied by 6.25.
With the increase in various types of diets, people usually skip on protein content food, hence everybody chooses to consume proteins in the synthetic form as supplements or protein powders. The use of supplemental amino acids or a general increase in total protein intake may be appropriate in disease-specific circumstances.
Conversely, in some conditions, such as renal failure or inborn errors of the urea cycle, a low-protein diet may be prescribed, but this does not mean that protein requirements have decreased; indeed, they may have increased. Similarly, various inborn errors of amino acid metabolism may result in the restriction of certain amino acids and possibly increased requirements for others.
For example, dietary phenylalanine should be restricted in patients with phenylketonuria but, due to a lack of tyrosine synthesis in such patients, tyrosine now becomes essential. Similarly, patients with inborn errors of the urea cycle (except a deficiency of arginase) require a source of arginine in the diet. It is therefore important to provide specific amino acids as appropriate for these and other inborn errors of amino acid metabolism.
Even though powdered forms of proteins can be found in natural foods such as eggs, milk, soya milk, etc. some synthetic protein powders contain a vegan option of mixtures that comes from different sources such as peas, pumpkin seeds, sunflower seeds, and alfalfa.
However, the companies to be opted from are crucial as some of them can contain non-protein ingredients including vitamins and minerals, thickeners, added sugars, non-caloric and artificial sweeteners, and flavoring.
It is advised to get the proteins from plants and meats equally. It includes all the legumes, nuts, and seeds such as almonds, pistachios, cashews, walnuts, hazelnuts, whole grains such as quinoa, wild rice, millet, oats, meat such as cooked chicken breast, low amounts of ground beef, and bacon.
Deficiency in Protein
It’s important to note that millions of people worldwide, especially young children, don’t get enough protein due to food insecurity. The effects of protein deficiency and malnutrition range in severity from growth failure and loss of muscle mass to decreased immunity, weakening of the heart and respiratory system, and death. As the protein holds the building blocks of life, our DNA deficiency in it is a serious concern.