Balancing Your Protein Intake: The Difference Between Complete and Incomplete Proteins

  • Post last modified:September 9, 2023
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Maintaining a healthy diet is perhaps one of the most critical factors in helping us lead healthier, happier, and longer lives.

The Difference Between Complete and Incomplete Proteins

When we talk about a healthy diet, it actually encompasses many aspects. Firstly, consuming natural foods rich in essential nutrients is crucial for sustaining the body’s normal functions.

We also need to pay attention to the intake of sugars and simple carbohydrates in our diet, as excessive consumption of these components can have adverse effects on our health.

Furthermore, protein is a vital part of our diet, playing a crucial role in maintaining the health of our muscles, tissues, and immune system.

However, it’s important to note that not all proteins are the same, and their absorption by the body can vary significantly.

Now, let’s delve into the differences between complete proteins and incomplete proteins, and how to consume protein to ensure it is absorbed and utilized by the body to the fullest.

The 20 Amino Acids that Compose Proteins

To understand the difference between complete and incomplete proteins, we first need to grasp what proteins are and why our bodies require them.

Our bodies rely on proteins to strengthen muscles, transport nutrients, repair tissues, and promote a healthy metabolism. Insufficient protein intake or a lack of all essential amino acids can lead to issues throughout the body.

Proteins consist of chains of amino acids, and the body requires the use of 20 different amino acids to maintain normal biological functions.

For example:

  • Proline: Used in the synthesis of collagen, the main structural protein in skin, joints, and tissues.
  • Serine: Involved in lipid metabolism, cell membrane construction, and the synthesis of antibodies and immunoglobulins.
  • Glutamine: Plays a crucial role in immune function and serves as one of the brain’s primary fuels.
  • Glycine: Involved in the synthesis of collagen, muscle tissue, and DNA.
  • Aspartic Acid: Used in the synthesis of nucleic acids, antibodies, and many essential proteins.
  • Tryptophan: An essential amino acid for serotonin production in the brain, contributing to mood regulation, appetite, and sleep.

Based on their source and whether the body can produce them or not, these 20 amino acids are categorized into “non-essential amino acids” and “essential amino acids.”

1. Non-essential amino acids

Non-essential amino acids are a category of amino acids that the human body can synthesize on its own.

Unlike essential amino acids, non-essential amino acids do not need to be obtained from the diet because the body possesses the biochemical mechanisms required to synthesize them.

Our body can produce 11 different non-essential amino acids using various compounds or metabolic pathways, including:

  • Alanine
  • Aspartic Acid
  • Asparagine
  • Arginine
  • Cysteine
  • Glutamine
  • Glutamic Acid
  • Glycine
  • Proline
  • Serine
  • Tyrosine

These amino acids play various vital biological roles in the body, including participating in protein synthesis, neurotransmitter production, antioxidant functions, tissue repair, and immune system support.

While they are non-essential amino acids, their presence is equally crucial for maintaining normal bodily functions and health.

Non-essential amino acids are typically synthesized within the body’s metabolic processes and do not need to be directly obtained from the diet.

However, in certain situations, such as specific medical treatments or certain health conditions, individuals may require additional intake of certain non-essential amino acids.


2. Essential amino acids

Essential amino acids are a group of amino acids that the human body cannot synthesize on its own and must obtain through dietary sources.

These amino acids are crucial for maintaining normal growth, cellular repair, healthy functioning, and metabolic processes in the body. Because the human body cannot produce these amino acids independently, they must be acquired through food intake to meet the body’s requirements.

There are 8 essential amino acids that the human body needs, and they are:

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

These amino acids play various critical roles within the body, including protein synthesis, immune system support, maintenance of muscle tissue, promotion of metabolism, and cellular function.

If any of these essential amino acids are lacking in the diet, it can lead to disruptions in protein synthesis, thereby affecting human health and growth.

What is The Difference Between Complete Protein and Incomplete Protein

What is The Difference Between Complete Protein and Incomplete Protein

Understanding the 20 different amino acids makes it easier to comprehend the difference between complete and incomplete proteins.

  • Complete proteins contain all the essential amino acids.
  • Incomplete proteins only contain some of the essential amino acids.

1. Complete Proteins

Complete proteins typically come from animal-based foods such as meat, fish, poultry, dairy, and eggs.

These foods contain all 20 different amino acids required by the human body, including the nine essential amino acids that cannot be synthesized by the body and must be obtained from food.

Complete proteins often have high biological value, meaning they provide all the necessary amino acids the body needs to support various physiological functions like muscle growth, immune system maintenance, and tissue repair.

2. Incomplete Proteins

Incomplete proteins typically come from plant-based foods such as legumes, grains, nuts, and seeds. These foods lack one or more of the nine essential amino acids.

Consuming foods with incomplete proteins alone may not provide a sufficient balance of all amino acids.

However, through a diversified diet, it’s possible to obtain the necessary amino acids because different plant-based foods often complement each other by providing the missing amino acids.

Complete proteins are easier for the human body to absorb and utilize because they contain all the essential amino acids. Incomplete proteins, on the other hand, are typically not as easily absorbed and utilized by the body.

According to research in Clinical Practice & Nutrition, individuals who regularly consume incomplete proteins, such as vegetarians, especially older individuals, may need to increase their daily total protein intake to meet their body’s needs.


Proteins are constructed from amino acids, which are the basic building blocks of proteins. Therefore, it’s essential for the diet to include an adequate amount of essential amino acids to ensure the body can synthesize various proteins it needs.

Complete proteins provide all the essential amino acids required by the body, supporting functions such as muscle growth, repair, and maintaining a healthy immune system. Incomplete proteins may lack some essential amino acids but still hold value as part of a diverse diet.

This is why a balanced diet is crucial to obtain all the essential amino acids. Some of the most common protein-rich foods indeed contain all essential amino acids, such as meats, fish, poultry, dairy products, legumes, and whole grains.

For vegetarians, aside from ensuring dietary diversity, obtaining enough essential amino acids can also be achieved through the use of dietary supplements.

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