The functions of proteins: Which foods contain protein?

The functions of proteins: Protein is one of the basic building blocks of living things and is of great importance for the continuity of life. It has many functions in the human body; therefore it must be taken enough. It is mostly found in animal foods such as meat, milk, and fish, but vegetable proteins should also be consumed. Disruption of the balance in protein intake may pave the way for the development of many diseases such as diabetes and cancer. In its deficiency, there are problems such as decreased body defenses and the inability to synthesize collagen. If taken too much, it may cause problems such as kidney and liver failure. For this reason, a regular amount of protein should be taken every day. It should not be forgotten that protein powders, which are generally used by athletes today, can have serious harm besides their benefits.

In this article, I will talk about The functions of proteins: Which foods contain protein? Benefits and harms, Protein deficiency causes, Protein deficiency symptoms, Protein deficiency treatment, What are a protein diet and Protein powder usage

If you are ready we go!

What is a protein?

Protein is an organic substance with a complex structure found in all living organisms. It has great nutritional value and takes part in many chemical processes essential for life. It is found in many tissues and structures of the human body, especially in muscle, bone, skin, and hair. It is also in the structure of enzymes that allows many chemical reactions to take place. The human body is made up of about 100 trillion cells, and each cell has thousands of different proteins that help them do its job. Proteins are like tiny machines inside the cell.

Amino acids and proteins

Amino acids are organic molecules containing carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Proteins are made up of amino acids linked together by long chains. Amino acids are the building blocks of protein. There are as many as 20 amino acids that makeup protein and they can be arranged in millions of different ways to create millions of different proteins, each with a specific task in the body. The sequence order of amino acids determines the function of the protein.

There are 20 different amino acids that the body uses to synthesize proteins. These are Alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine.

Protein Types

  1. Complete proteins: These foods contain all essential amino acids. It is often found in animal foods such as meat, dairy products, and eggs.
  2. Missing proteins: These foods contain at least one essential amino acid. Plant foods like peas, beans, and grains often contain incomplete protein.
  3. Complementary proteins: Here, two or more incomplete protein-containing foods come together to form a complete protein. For example; beans and rice or peanut butter bread.

What is arginine? What does arginine do?

The functions of proteins: Which foods contain protein?

The functions of proteins

The functions of proteins: Basic functions of proteins in the body; are to build, strengthen, repair, or produce new tissue. Proteins play a role in almost every biological process and have a large number of different functions. Some of these are listed below The functions of proteins::

  • It produces collagen-like structures.
  • It is found in the structure of hormones such as insulin.
  • It is included in substances with transport properties such as hemoglobin.
  • It forms the structure of enzymes such as amylase.
  • It plays a role in the transport of molecules in the body.
    Provides the repair of cells.
  • It plays a role in protecting the body from viruses and bacteria.
  • It provides a growth function, especially in children and young people.

Keratin is a structural protein that strengthens protective coatings such as hair. Collagen and elastin also have a structural function and also provide support for connective tissue.

Which foods contain protein?

  • Animal proteins (in 100 g)
  • Lean beef: 36 gr.
  • Cheese: 32 gr.
  • Tuna Fish: 26 gr.
  • Salmon: 26 gr.
  • Chicken: 18.3 gr.
  • Yogurt: 6 gr.
  • Milk: 6 gr.
  • Egg: 13 gr.
  • Vegetable proteins (in 100 g)
  • Quinoa: 14 gr.
  • Beans: 8 gr.
  • Peas – 5.4 grams per 100g
  • Spinach (cooked): 3 gr.
  • Corn: 3.3 gr.
  • Broccoli: 2.8 gr.
  • Brussels sprouts: 2.6 gr.
  • Asparagus: 2.4 gr.
  • Hazelnuts, peanuts, almonds

Soy Proteins: Soy, a popular plant-based protein, is an exception. Soy is a complete protein that contains all of the essential amino acids. High protein foods from soy:

  • Tempe: 19 gr.
  • Miso: 12 gr.
  • Edamame: 11 gr.
  • Tofu: 7 gr.
  • Soybeans: 17 gr.
  • Nuts / Seeds: 33gr.

Foods containing harmful protein

  • Processed meat
  • Fried meat
  • Sugar yogurt
  • Processed salmon
  • Whole wheat or grain bread
  • Tofu deli meats
  • Nuts or peanuts covered in sugar
  • Processed protein bars
  • Ready peanut butter
  • Too much cheese
  • Ramen noodles
  • White pasta

Animal and vegetable protein differences

  • The amino acid profile varies between plant and animal proteins: Animal proteins provide all the amino acids we need in a balanced way, but some plant proteins are poor in certain amino acids. For example, some essential plant proteins are generally low in methionine, tryptophan, lysine, and isoleucine. However, some plant-based foods like quinoa and buckwheat contain full protein sources.
  • The animal protein source is higher than the nutritional values of animal sources of protein, vitamin B12, vitamin D, and omega-3 fatty acid DHA, both Iron and zinc are richer in some foods.
  • A diet rich in plant protein protects from some diseases: A diet high in plant protein is protective against health problems such as heart disease, diabetes, and obesity. It contains fiber and protects against digestive system diseases. Animal diets, especially processed meat, can increase the risk of cholesterol and heart disease.
  • Animal protein also has some health benefits: Some sources of animal protein aid weight loss and increase muscle mass.
  • Protein intake in athletes: Athletes generally prefer protein powder with high protein content to maintain their muscle mass. However, it has been suggested in a study that rice protein isolate, which is one of the vegetable proteins, may provide a similar effect to protein powder.
The functions of proteins: Which foods contain protein?

What are the benefits of protein?

  • Protein-rich foods keep you full and provide fewer calories.
  • It helps to maintain muscle mass and strengthen muscles. It can reduce muscle loss that may occur while losing weight.
  • It protects bones. It reduces the risk of osteoporosis and bone fractures.
  • Eating a protein-rich diet reduces the desire to snack at night.
  • A high-protein breakfast will make you more energetic throughout the day.
  • It speeds up the metabolism and allows you to burn more calories throughout the day.
  • It lowers high blood pressure and bad cholesterol.
  • Protein can harm people with kidney problems, but not people with healthy kidneys.
  • Helps you recover faster after being injured
  • It reduces the muscle loss associated with aging.

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What is your daily protein requirement?

We need protein for muscles, bones, and the rest of the body. Daily protein requirements may vary with age. The minimum amounts that the body should take daily according to age:

  • Babies: 10 gr.
  • School-age children: 19-34 gr.
  • Adolescent boys: 52 g
  • Adolescent girls: 46 gr.
  • Adult males: 56 gr.
  • Adult females: 46 gr.
  • Pregnant or breastfeeding
  • Women: 71 gr.


According to the Institute of Medicine, you should get at least 10% and a maximum of 35% of your daily calories from protein.

Protein deficiency causes

Deficiency due to low protein intake in the diet is a more common health problem in underdeveloped countries, unlike developed countries. The following health problems can cause protein deficiency:

  • Eating disorders (e.g. anorexia nervosa),
  • Genetic
  • Later stages of cancer
  • Irritable bowel syndrome
  • Having gastrointestinal surgery

Protein deficiency symptoms

  • Feeling tired or sick
  • Very frequent viral or bacterial infections
  • Thinning, breakage, or loss of hair
  • Cracked nails and dry skin
  • Mood changes such as irritability
  • Cravings for protein-rich foods


These symptoms are also similar to those of other health problems, such as iron deficiency anemia or an immune system problem. Therefore, tests should be done for the correct diagnosis.

Diseases caused by protein deficiency

  • Kwashiorkor: A type of protein deficiency that affects young people. If left untreated, it can hinder the mental and physical development of the patient.
  • Marasmus disease: It is a disease that causes muscle and fat loss in children as a result of protein deficiency.
  • Mental impairment
  • Organ failure
  • Loss of muscle mass in adults
  • The weakening of the immune system
  • Hormone imbalances
The functions of proteins: Which foods contain protein?

Protein deficiency treatment

Treatment is determined directly by the cause of the protein deficiency. A detailed medical history, physical exam, and tests may be required to determine what is causing the deficiency. Afterward, the appropriate treatment method is determined.

  • A person with an eating disorder may need to be treated for this so that they can switch to a healthy, balanced diet with adequate protein.
  • Someone with celiac disease will need to follow a gluten-free diet so that nutrients, including proteins, can be properly absorbed in the small intestine.
  • Liver and kidney diseases often require regular follow-up by the doctor, extensive medical treatment, and further follow-up.
  • Pregnant women with extreme nausea and vomiting may need treatment to relieve their symptoms so they can consume enough calories and protein for the healthy development of their babies.

Diseases in protein excess

Excessive intake of protein can cause the following:

  • Gaining weight
  • Bad breath
  • Constipation
  • Diarrhea
  • Loss of water
  • Kidney damage
  • Kidney stone
  • Increased risk of cancer
  • Heart diseases
  • Calcium and bone loss
  • Liver complications


For all these reasons, meat-heavy diets can be dangerous and increase a person’s risk of developing coronary heart disease, and breast, bowel, and prostate cancer.

What is a protein diet?

Normally, your body burns carbohydrates for energy. When carbohydrates are suddenly cut, the body enters a metabolic state called ketosis and starts burning fat to provide energy. When your primary source of energy is fat stores, you begin to lose weight.

Low-carbohydrate diets with high protein consumption are recently recognized as one of the effective weight loss methods. This diet program usually recommends that the person get 30% to 50% of their total calories from protein.

Protein diet harms


The American Heart Association, the National Cholesterol Education Program, and the American Cancer Society have stated that high-protein and low-carbohydrate diets pose health risks. We can list these risks as follows:

  • High cholesterol: Certain protein-containing foods (such as fatty cuts of meat, dairy products, and other fatty foods) can increase bad cholesterol, which can increase the risk of heart disease.
  • Kidney problems: If you have kidney problems, eating a high-protein diet can tire your kidneys and worsen kidney function.
  • Osteoporosis and kidney stones: When following a high-protein diet, you can excrete more calcium than normal in your urine. There are conflicting reports on this issue, but some experts think this increases the risk of osteoporosis and kidney stones.

If you are considering a high-protein diet, consult a doctor or a nutritionist to determine if it is right for you.

Protein powder usage

The functions of proteins: Protein powder is generally used by athletes and those who want to improve their bodies. With protein powder, they get the protein that should be taken daily, fast, and ready. Protein powder obtained by isolating whey is preferred because it enables athletes to build muscle faster.

Protein powder damages

Protein powder, which is also recommended by some sports trainers, is actually not considered very healthy. It is a supplement that functions outside of the body’s natural balance and can even cause death when consumed in excess. In general, the following situations may occur in excess protein intake:

  • May cause acne
  • Antibacterial compounds such as lactoferrin found in whey can damage the intestinal flora and, as a result, cause gastrointestinal problems.
  • Protein powder produced by some companies other than well-known brands may contain highly toxic metals such as lead, cadmium, arsenic, and mercury. These metals can cause headaches, muscle and joint pain, fatigue, and constipation.
  • Consuming post-workout protein powder can cause increased insulin levels.
  • It contains protein concentrated relative to natural protein sources, resulting in nutrient composition imbalance.

What does L-Carnitine do? L-Carnitine Guide

Resources and References:

1- Protein for Life: 2- How to increase the protein in your diet, 3- Protein 4- Dietary Proteins

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