8 Functions of Protein in Human Body

Protein is one of the three macro-nutrient present in the food that the body requires in large quantities. It is important for the maintenance and development of body tissues and muscles. Proteins include amino acids that form long chains together. There are 20 amino acids that help make different proteins. However, protein does most of its cell work and other functions inside the body. Here are 8 crucial functions of protein in the human body.

1. Protein Provides Energy

Proteins provide energy to your body. One gram of protein contains four calories, the same energy provided by carbs. Fats give the most energy, nine calories per gram. As we commonly use carbs and fat for energy, the last thing the body wants to use for energy is protein. Carbs and fats are much better suited for energy supply, as your body has a reserve for them. In fact, they are more metabolized compared to protein [1].

Protein provides the body under normal circumstances with very little of its energy. Your body breaks down the skeletal muscle in a state of fasting so that the amino acids can provide you with energy [2], [3]. Your body also breaks down skeletal muscle amino acids if the storage of carbohydrates is low. This can happen after intensive exercise, or calorie restriction [4].

One gram of protein contains four calories, the same amount of energy as carbohydrates. Carbohydrates and fats are better suited for energy supply because your body stores them. They are, in fact, more metabolised than protein.

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Related article: 22 delicious high-protein foods you should eat.

2. Provides Structure

Some proteins are fibrous, giving rigidity to cells and tissues. Such proteins include keratin, collagen, and elastin, which help to shape the connective tissue within your body of certain structures [5]. Keratin is a protein found in your skin, hair, and nails [6]. Collagen is your body’s most abundant protein in your bones, tendons, ligaments, and skin.

Elastin is a hundred times more flexible than collagen. Upon stretching or contracting, most tissues in your body will return to their original forms, such as your uterus, lungs, and arteries [7].

Fibrous proteins are a type of protein that provides structure, strength, and elasticity to various parts of your body.

3. Boosts Immune Health

Proteins help to prevent infection by forming immunoglobulins or antibodies [8], [9]. Antibodies are blood proteins that help protect the body from dangerous invaders such as bacteria and viruses. Your body produces antibodies for elimination of these invaders inside your cells [10]. Bacteria and viruses multiply and overwhelm your body without these antibodies.

Once your body produces antibodies to a specific bacterium or virus, your cells will never forget how to make them. This enables the antibodies to respond if a specific virus or bacteria invades the body [11]. As a result, the body develops immunity to the diseases it is exposed to [12].

Antibodies are blood proteins that aid in the body’s defence against harmful invaders such as bacteria and viruses. Your body creates antibodies to fight these invaders within your cells.

4. Muscle Growth and Maintenance

Your body needs protein for many functions, such as muscle growth and maintenance. Yet the proteins of your body are in constant turnover. The body breaks down the same amount of protein it uses to build and rebuild tissues under normal circumstances.

Sometimes your body breaks down more protein many than it can produce, thus increasing the needs of your body. However, this occurs during illness, pregnancy, and breastfeeding cycles [13], [14], [15]. Keep in mind, older adults and athletes also need more protein to recover from injury or exercise [16], [17], [18].

When your body breaks down more protein than it can make, your body’s demand for protein increase. This occurs during periods of illness, pregnancy, breastfeeding, or exercise.

5. Proper pH Levels

Protein plays a vital role in controlling blood and other body fluid levels. The pH scale is used to measure the balance between acids and bases [19], [20]. It is between 0 and 14, with 0 being the most acidic, 7 neutral, and 14 being the most alkaline [21]. Several buffering systems can preserve normal pH levels for your body fluids.

Your body needs a constant pH level because even a slight pH change can be harmful or deadly [22], [23]. Proteins are one way to control the body’s pH level. Hemoglobin, a protein that shapes red blood cells, is an example. Hemoglobin binds small amounts of acid to help maintain the blood’s usual pH level. Phosphate and bicarbonate are the other buffer structures in your skin [24].

Proteins function as a buffer mechanism, helping your body to maintain proper pH levels in your blood and other physiological fluids. Because even minor pH changes can damage to your body, and the body requires a steady pH level.

6. Transports Nutrients

Transport proteins carry molecules throughout the bloodstream, into, out of, or inside cells. Nutrients such as vitamins or minerals, blood sugar, cholesterol, and oxygen are the substances transported by these proteins [25], [26], [27]. Hemoglobin, for example, is a protein that carries oxygen to body tissues from your lungs. Glucose transporters (GLUT) carry glucose to your cells, while lipoproteins carry cholesterol and other fats in your blood. Protein carriers are unique, so they only bind to particular substances.

A protein that carries glucose will not carry cholesterol. Protein also has functions in the storage [28], [29]. For instance, ferritin is a protein that makes iron available for vital cellular functions while shielding lipids, DNA, and proteins from potentially toxic effects of iron [30]. Another protein that is processed is casein, which is the key milk protein that helps babies grow.

Proteins act as transporters of nutrients, such as vitamins or minerals, blood sugar, cholesterol, and oxygen.

7. Balances Fluid Levels

Protein regulates the body to maintain fluid balance. Albumin and globulin are blood proteins that help keep the fluid balance of your body by attracting and keeping the liquid [31], [32]. If you don’t consume enough protein, your albumin and globulin levels will fall. As a result, these proteins can no longer hold blood in your blood vessels and the fluid is pushed into the gaps between your cells.

The fluid keeps building up in the spaces between your cells. Swelling or edema will occur in the belly region [33]. This is severe protein malnutrition called kwashiorkor, that develops when a person consumes a lot of calories but does not consume sufficient protein [34]. Kwashiorkor is rare in the developed countries and present in the countries where poverty is at its peak.

Protein controls the body’s fluid levels. Albumin and globulin are blood proteins that aid in the maintenance of your body’s fluid balance.

8. Biochemical Reactions

Enzymes are proteins that support millions of biochemical reactions occurring inside and outside the cells [35]. The enzyme structure allows them to interact inside the cell with other molecules called substrates, a catalyzing reactions important to your metabolism [36]. However, enzymes may function outside the cell, such as digestive enzymes, lactase, and sucrase, which help digest sugar.

Many enzymes require other molecules for a reaction, such as vitamins or minerals. Bodily functions depend on enzymes such as digestion, energy production, blood clotting, and muscle contraction. [37]. Lack of these enzymes may lead to disease [38].

Enzymes are proteins that aid in millions of biological events that occur both within and outside of cells. A lack of these enzymes may cause illness.


Protein has many functions inside the human body. This helps to stabilize and build the tissues of your body, enables metabolic reactions to occur, and regulates body functions. Besides providing a structural foundation for your body, proteins also maintain proper pH and fluid balance in the body. They keep your immune system healthy, carry and store nutrients, and they can serve as an energy source. However, proteins are the building blocks of life and the most important nutrients.

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