What are proteins?

 Outcomes of this article are:

What are proteins?
Functions of protein, different types of amino acids, classification of proteins, protein requirements, and proteins and vegetarians. 

What are proteins?
Proteins are made up of amino acids, which are like building blocks. 

There are 20 different amino acids that join together in various combinations to make all types of proteins. 

Functions: 

Protein is an essential nutrient for your body. Proteins are the building blocks of body tissue and can also serve as an alternate source of fuel when needed. Your body uses protein for growth and maintenance. 

Proteins also function as enzymes in membranes and as transport carriers and hormones; their components serve as precursors for nucleic acids, hormones, vitamins, and other integral molecules.

One gram of protein contains four calories. 

Proteins and Amino Acids 

Proteins are made up of amino acids. Some of these amino acids can't be made by our bodies, hence they are known as essential amino acids because it is essential that our diet provide them. In terms of diet, protein sources are categorized according to how many of the essential amino acids they provide. 

Non-essential amino acids are that can be made by our bodies so they are not essential to provide in diet and semi-essential amino acids are that have to be consumed in the diet under special circumstances. 

So, a complete protein source is one that provides all of the essential amino acids. Complete proteins are also referred to as high-quality proteins. Animal-based food sources such as meat, poultry, fish, milk, eggs, and cheese are complete protein sources. 

An incomplete protein is one that is low in one or more of the essential amino acids. Plant-based food sources such as grains, lentils, and rice are incomplete proteins. 

Complementary proteins are two or more incomplete protein sources that together provide adequate amounts of all essential amino acids. For example, rice contains low amounts of the amino acid lysine and high amounts of the amino acid methionine; however, dry beans contain greater amounts of lysine and lesser amounts of methionine. Together, these two food sources can provide adequate amounts of all the essential amino acids required by the human body.
 

Protein Requirements for Sedentary Versus Active Individuals 

The main factors that determine how much protein an individual needs are training regime and habitual nutrient intake. At the same time, current literature suggests that it may be too simplistic to rely on current recommendations for daily protein intake. There are various factors that need to 

be considered, such as the quality of proteins according to the biological value of the source, caloric intake, exercise intensity, duration and type of exercise, training history, gender, age, etc. 

Currently, the RDA for protein intake is 0.8 grams per kilogram of bodyweight, which is based on the needs of sedentary individuals; this represents an intake level necessary to replace losses and avert deficiency. 

Numerous studies indicate protein requirements for active individuals are approximately double that of the RDA—at least 1.4 – 2.0 grams per kilogram of bodyweight. 

Protein Recommendations 

RDA guidelines for protein intake are less than the amount actually required for active individuals and should thus be adjusted according to one’s type of activity. Aim to consume at least 1.4 grams/kg/day of protein from various foods to get all the essential amino acids. 

Proteins and Vegetarians 

Contrary to popular wisdom, plant-based protein, when combined together, is as powerful as animal-based proteins. But you need to eat a variety of plant-based food to ensure that you get all essential amino acids that are required by the body. 

 

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