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What Is Protein?


What Is Protein?

Proteins are often called “the building blocks of life” — and for good reason. They are complex molecules that play more important roles in your body than you can imagine.

Protein makes up the bricks and mortar of your body. It is incorporated into every one of your muscles, organs, and tissues. It is also essential for your body to create energy and function properly overall. Hormones, antibodies, transport and storage systems, and enzymes that trigger millions of chemical reactions each day are made from proteins.

To maintain the structure and function of the proteins throughout your body, you must eat enough of the right types of protein foods as part of a balanced diet.

What is The Function of Protein?

As an essential macronutrient, protein functions along with fats and carbohydrates. Each plays a different role in your body, but they also work together to keep you healthy.

Carbohydrates provide the glucose that fuels your muscles and brain. Carbs come from foods that are high in starches and sugars, such as fruits, potatoes, corn, squash, peas, beans, and grains.

Fat makes up the linings of all your cells, and it is used to produce many hormones. It also insulates your organs, helps absorb certain vitamins, and serves as an important fuel source. The healthiest fats come from nuts, seeds, and oils as well as foods such as oily fish, avocados, and olives.

While carbs and fats are essential, they would not have much of a role without protein. If you think of your body as a complex machine, all the major parts, as well as the technology that runs the machine, are made from protein. To prevent your machine from breaking down, or to repair it when it does, you need a steady supply of protein foods from your diet.

Protein Starts With Amino Acids

All protein, including the proteins that make up your body and the protein you eat, is made from smaller molecules called amino acids. They are like individual letters in the alphabet. Depending on how they are combined, you can make words, sentences, or paragraphs. Amino acids can be assembled in countless ways to make different types of simple or complex proteins in your body depending on whether your body needs to build more muscle, make more red blood cells, boost your immune system, or do anything else it needs to survive and thrive. Since much of the protein we absorb does so as di and tripeptides, the configuration of amino acids in these smallest peptides is important. Animal proteins will have di and tripeptides that are different than plant proteins, one of the issues that make plant proteins less efficient for human nutrition.

There are 20 different amino acids that make up the different proteins in your body. You make many of the amino acids as long as you are eating a healthy diet and have enough of the basic nutrients available. The amino acids you make are called nonessential amino acids.

However, nine amino acids are considered essential. You have to get them from your diet because your body cannot make them. The essential amino acids include:

  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine

There are other amino acids, such as arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine, which are considered conditional amino acids. While they are not essential and you can make them, they are easily depleted when you are sick or under stress, so you can’t go wrong by supplementing them through your diet.

Why Is Protein Important?

Protein foods are important because they provide the nutrients you need to make nonessential amino acids, and they supply the essential amino acids you must get from your diet.

If you are protein deficient, every part of your body is affected since protein plays so many different roles. You will lose muscle mass because your body needs to break down muscle tissue to free up amino acids for other more important functions. You may be more susceptible to illnesses because your immune system is protein-dependent. You may not heal easily from cuts or wounds because skin and collagen are also made from proteins.

However, it is rare to be truly protein deficient if you are young and healthy. What is more common is for your protein to be unbalanced. That could happen if you are not eating enough protein, if you are not absorbing it properly, or if you are not getting an ideal protein. Your body will not work as well as it could. Most importantly, your energy level, metabolism, and weight could suffer.

One of the most important reasons to focus on getting ideal protein is that eating more protein helps maintain lean body mass (aka muscle), which in turn is associated with a healthier weight and a healthier body, especially as you age.

Sources of Protein:

You can get protein from both animal and plant sources. Foods that provide protein include meats, poultry, fish, eggs, nuts, dairy, and beans or legumes. While both sources of protein are important and good for you, they are not created equal.

Protein that comes from animals, such as meats, poultry, fish, eggs, or dairy foods, is complete protein. That means when you eat any of these protein foods, you get all your essential amino acids. Animal foods are packed with protein. In general, you can get more protein from less food.

Of the animal proteins, whey, which comes from dairy foods, is considered an ideal protein. Not only does it provide all the amino acids you need, but it also does a great job of maintaining your muscles. Many consider whey to be the premier protein.

Protein that comes from plant foods, such as tofu, beans, vegetables, plant milk, nuts, or seeds, is an incomplete protein, which means it is lacking one or more of the essential amino acids. However, there’s no need to worry about your protein quality as long as you’re eating a variety of foods. Any amino acids that are lacking from one food will be supplied by other food.

Although plants have many health benefits, one drawback is that they tend to be lower in protein, so if you are looking to consume more protein strictly from plant foods, you will also have to eat a larger quantity of food, which means more overall calories and additional wear on the lining of the small intestine.

Protein supplements in the form of powders, shakes, or protein bars can be made from either animal or plant proteins. Some common types of animal proteins include whey, casein, egg, or collagen. Plant proteins can be made from any type of plant, but most contain a mix of protein sources such as soy, pea, hemp, or rice. A major plant protein issue rarely discussed is the amount and types of antinutritive factors contained in plant protein whether raw or processed. Plants might seem to be passive and as good as animal food, but evolution has produced significant antinutritive devices to dissuade plant-eaters from growing on plant foods, and consequently, evolution has equipped plant-eaters with all sorts of devices to defeat innate plant defenses. Humans have no such advantages.

Digestion of Protein

Before you can use the amino acids that your protein provides, you have to digest it. Some types of protein may be easier for you to digest than others.

Protein digestion starts in your stomach where acid and enzymes begin to unwind and break apart or denature strands of protein into di and tripeptides. These smaller protein fragments pass through the microvilli in your small intestine where they are released into your bloodstream and shipped off to work where they are needed. Most protein will be delivered into the blood as di and tripeptides, which is much more efficient than amino acid delivery.

Whole protein foods take a bit of work to be digested, but one way to make the process easier is to eat (or drink) hydrolyzed protein. Hydrolyzed protein is broken apart, or partially digested, even before you eat it. The advantage of hydrolyzed protein is that your body has less work to do, so the protein is absorbed and used much quicker and there is little propensity for losing protein as waste or generating intestinal distress like gas and bloating.

If you are exercising regularly, hydrolyzed whey protein gets to your muscles faster to help with muscle synthesis and recovery. It has been shown to stimulate muscle synthesis after a workout better than other forms of protein, so it is an ideal protein.

If you have problems digesting larger proteins, hydrolyzed proteins are a better choice. Hydrolyzed protein, especially from a quality protein bar, is also a great choice when you need your protein but do not have a big appetite, because it packs a powerful punch with minimal calories. A protein bar or supplement not only provides the right type of protein for you, but it is also nicely packaged with healthy carbs and fat so that protein works better for you.

The Bottom Line

Protein is an essential nutrient that makes up much of the structure and function of your body. It is important to get enough high-quality protein each day from a variety of foods and supplements, if needed.

If you are looking for a premier protein source that is easily digested and absorbed and gets right to work for you, hydrolyzed whey protein is one of the best options available.


  1. Amino acids:
  2. Protein leverage and energy intake:
  3. Influence of amino acids, dietary protein, and physical activity on muscle mass development in humans:
  4. Whey Protein Hydrolysate Increases Amino Acid Uptake, mTORC1 Signaling, and Protein Synthesis in Skeletal Muscle of Healthy Young Men in a Randomized Crossover Trial:
What is protein? infographic



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