PROTEINS – Definitions | Sources | RDA | Types and Functions | Deficiency

The human body contains about 100,000 different proteins produced by different combinations of 20 amino acids. Approximately 18-20% of body weight is due to proteins. This sounds like crazy, right?

Yes, proteins are very important for our body to work properly and effectively. If you want to understand its importance to include in your daily diet, you should have the overall idea about proteins. 

In this article, I will discuss Definitions, sources/examples, recommended daily allowance, types and functions, and deficiency diseases and symptoms of proteins and amino acids.

★ So, What are proteins?

First, let me know you about nutrition. In simple language nutrition is food. Nutrition is of two types. Macro & micro.

The macronutrients are nutrients that required to the body in a large amount. Macronutrients are of three types: carbohydrates, proteins, and fats.

And the micronutrient is a nutrient that required to the body in a small amount. Micronutrients are of two types: Vitamins and Minerals.

Proteins are made up of small compounds called amino acids. There are hundreds of amino acids present in nature. But only 22 of them are utilized by the body.

★ What are Amino Acids?

Amino acids are the building blocks of all biological proteins. The amino acids are linked together by peptide bonds in a specific order defined by genes. The genes are translated from RNA to amino acids; the length and order of the amino acid chain give the three-dimensional structure of a polypeptides or proteins.

Non-Essential Amino Acids: Our body able to produce 13 out of 22 amino acids. So these are called Non-Essential Amino Acids (not essential to be consumed daily).

Essential Amino Acids: 9 out of 22 amino acids are not produced by the body, so continuous supply of these are necessary to stay healthy and fit. These are called Essential Amino Acids (essential to be consumed daily).

Semi-Essential Amino Acids: 2 out of 9 essential amino acids are called semi-essential because these are synthesized by adults and not by growing children.

Conditional Amino Acids: When we’re sick or under extreme stress or trauma, our body may not be able to produce some amino acids, and need to be consumed, these are called conditional amino acids. Some debates are here regarding the number of conditional amino acids. Some researchers are told the number is six, some told seven or some told eight.

amino acids, protein, FabHealthFitness,

★ Sources or Examples of Proteins 

✪ Meat and Poultry: Chicken breast, Turkey, Pork, Beef etc.
✪ Eggs and Dairy: Egg, Cheese, Milk, Yogurt etc.
✪ Fish and Seafood: Tuna, salmon, Catfish, Cod, Lobster, Oyster etc.
✪ Beans and Legumes: Chickpeas, Lentils, Tofu, Soybeans, etc.
✪ Nuts and Seeds: Peanut, Almonds. Cashews, Flax seeds, Sunflower seeds, Brazil nuts, etc.

Top 10 Best Proteins Foods

FoodsServing SizeAmount of Protein
Turkey and chicken breast100g30g
Halibut, salmon, tuna100g26g
Pork loin100g25g
Lean meat100g36g
Yogurt and milk100g6g
Nuts and seeds100g33g


Vegetarian Protein foods, foods, source, FabHealthFitness

Top 10 Proteins Foods for Vegetarians

FoodsServing SizeAmount of Protein
Low-fat flat bread like tortillaEach30g
Kidney Beans200g15g
Baked beans200g12g
Almonds¼ cup portion8g
Peanut butter30g7.5g
Soy milk8 oz7g
Dried apricots8 oz5g
Avocado8 oz5g


★ Recommended Daily Allowance 

Proteins should be in your diet every day because it is constantly broken down and replaced. The human body cannot store proteins like it stores carbohydrates and fats. 

✪ Kids need about 10 grams a day.
✪ School-age children need 19-34 grams a day.
✪ Teenage boys need up to 52 grams per day.
✪ Teenage girls need 46 grams per day.
✪ Adult men need about 56 grams a day.
✪ Adult women need about 46 grams a day (71 grams, if you are pregnant or breastfeeding)

Each gram of proteins provides 4 calories. So, You should get at least 10% of your daily calories from proteins, but not more than 35%, according to the Institute of Medicine.

✪ For Bodybuilders: Academy of Nutrition and Dietetics reports that bodybuilders require 1.4 to 1.7 grams of protein per kilogram or about 0.63 to 0.77 grams of protein per pound of bodyweight each day. 

★ Types and Functions of Proteins

According to function and role that plays proteins in our body, they are classified into 7 categories. And each of them has different functions.

1. Contractile or Motor proteins

They are responsible for transport of nutrients in cells, cell divisions, the genetic makeup, heart and muscle contractions.

Example: Actin and Myosin together produce muscle contractions.

2. Defensive proteins

Antibodies or immunoglobulins are made by proteins and are a core part of our immune system. They are produced in white blood cells (WBC) and fights against bacteria, viruses, and microorganisms.

Examples: Fibrinogen and Thrombin are responsible for blood clotting.

3. Enzymatic proteins

Enzymatic proteins or simply called enzymes are catalysts of biochemical reactions of our body. They accelerate the metabolic process in our cells, liver functions, digestions, blood clotting etc.

Examples: Amylase and Pepsin are enzymatic proteins or enzymes that are responsible for digestion of starch and proteins respectively.

4. Hormonal proteins

Hormonal proteins or simply called hormones are a type of chemical messenger which transmit signals from one cell to another. Each hormone targets or affects certain cells in our body so-called target cells. They are responsible for initiate or influence or coordinate a specific metabolic process in our body.

Example: Oxytocin, a female hormone that stimulates the contraction during childbirth. Another example is Insulin. Which regulates the blood glucose level.

5. Storage proteins

This protein mainly stores nutrients like amino acids and energy-rich molecules like potassium, irons etc for later use.

Example: Casein is a storage protein, found in the milk of mammals, which stores amino acids, carbs, phosphorus, and calcium.

6. Structural proteins

Also called fibrous proteins, structural proteins maintain structure and provide support to the human anatomy.

Example: Collagen is a structural protein that forms a connective framework of muscle, bones, tendon, skins and cartilage. Keratin also a structural protein which is a main structural component of hair, nails, teeth and skins.

7. Transport proteins 

These types of proteins are transport various molecules and nutrients around the body and in & out of cells.

Example: Haemoglobin in red blood cells (RBC) picks up oxygen from the lungs and deliver it to all the tissues in our body. Lipoproteins transport lipid or fat.

Last Function: Providing Energy | Works like a Carbs

It happens only when you do not consume sufficient amounts of carbs that will fulfill your energy needs. In this case, proteins will break down to provide energy. If it is not needed, proteins can convert and stored as fat.

★ Proteins Deficiency

First, let’s discuss Proteins Deficiency Diseases

Proteins are building blocks of the body. They provide the energy needed for the body to function properly and are crucial for the development of muscles. The proteins also facilitate the development of nails, promote healthy skin and hair growth. Lack of proteins has many side effects and can lead to medical conditions if untreated.

1. Marasmus Marasmus, protein deficiency, FabHealthFitness

Children and infants are vulnerable to the consequences of the lack of proteins. Marasmus is a serious lack of important nutrients. Food4Africa notes that people suffering from marasmus seem fragile and thin. This is a dangerous disease that causes weight loss and dehydration. 

2. KwashiorkorKwashiorkor, protein deficiency, FabHealthFitness

The lack of protein sources of carbohydrates such as rice, potatoes, and bananas cause kwashiorkor. It’s a serious disease of malnutrition common in older children. The University of Maryland Medical Center explains that the symptoms of this disease include a bloated stomach due to fluid retention. Its symptoms are common as Marasmus including irritability, diarrhea, limited growth and cognitive development as well as mental health.

3. The protein C and protein S deficiency

Research indicates that 1 in 300 people suffer from lack of proteins C. Similarly, the protein S deficiency affects 1 in 20,000 people. MedlinePlus states that the lack of protein C and protein S is an inherited disease that leads to blood clotting. These deficiencies are characterized by pain, redness, swelling and tenderness in the affected region.

What is Protein C  and Protein S? : Test for protein C and protein S are two separate tests that are performed together to investigate the possible excessive clotting disorder (hypercoagulable). It also uses to diagnose the cause of inadequate clots such as deep venous thrombosis (DVT) or venous thromboembolism (VTE).

4. CachexiaCachexia, FabHealthFitness

This is a condition involving protein deficiency, skeletal muscle fatigue, and an increased protein degradation rate. Cachexia causes weight loss and mortality associated with cancer, AIDS, chronic renal failure, heat illness, chronic obstructive pulmonary disease and rheumatoid arthritis.

Protein deficiency symptoms

The lack of proteins showed signs and symptoms of changes in the body. If you experience any of the symptoms or you notice someone with signs, you should immediately consult a doctor. Some of these symptoms include:

✪ Weak and sore muscles,
✪ Increased water retention,
✪ Flakiness, dry skin, and rashes,
✪ Lethargy,
✪ Weight loss,
✪ Anxiety,
✪ Nausea,
✪ Skin ulcers,
✪ Formation of deep line around the toes and nails,
✪ Stubborn nonhealing wounds,
✪ Constant headaches,
✪ Changing feelings,
✪ Blackouts,
✪ Depression,
✪ Changes in skin color.

So, now I think you got an overall idea about Proteins. Please tell me how much you like this article. Comment down about you thoughts, doubts, questions and suggestions.

Like this post? Share it with your friends! 

You can also find us on YouTube, Twitter, Facebook, LinkedIn, Instagram, Google+.


PROTEINS – Definitions | Sources | RDA | Types and Functions | Deficiency
5 (100%) 8 votes
Follow me

A. R. Choudhury

Hi, This is A. R. Choudhury, a professional blogger & fitness expert from New Delhi, India.

Here at FabHealthFitness, I write about Health, Fitness, Bodybuilding, Supplements and Diet & Nutrition.

You can read more about me at About us page.
Follow me

Comments 1

Leave a Comment