Difference Between Complete and Incomplete Proteins

Main Difference – Complete vs Incomplete Proteins

Proteins are the second most plentiful substance in the human body. The building blocks of a protein are the amino acids. There are two types of proteins as complete and incomplete proteins. The main difference between complete and incomplete proteins is that complete proteins supply all essential amino acids to the body whereas incomplete proteins only supply some amino acids. Animal sources of proteins such as fish meat, poultry, eggs, and dairy products contain complete proteins. Soybeans and quinoa also contain complete proteins. Non-animal food such as nuts, beans, legumes, and tofu contain incomplete proteins.

Key Areas Covered

1. What are Complete Proteins
      – Definition, Significance, Sources
2. What are Incomplete Proteins
     – Definition, Significance, Sources
3. What are the Similarities Between Complete and Incomplete Proteins
      – Outline of Common Features
4. What is the Difference Between Complete and Incomplete Proteins
      – Comparison of Key Differences

Key Terms: Animal Proteins, Complete Proteins, Contemporary Protein, Essential Amino Acids, Incomplete Proteins, Plant Proteins

What are Complete Proteins

Complete proteins are a type of proteins which contain all essential amino acids in the correct ratio for humans and other animals. The human body needs twenty amino acids for protein synthesis. Eleven of them are synthesized by the body. The remaining nine amino acids should be obtained by food. These amino acids are called essential amino acids. Complete proteins contain all essential amino acids within the same source. Tryptophan, threonine, isoleucine, leucine, lysine, methionine+cyctine, phenylalanine+tyrosine, valine, and histidine are the nine essential amino acids

Difference Between Complete and Incomplete Proteins

Figure 1: Food containing Complete Proteins

Proteins that are derived from animal sources are complete proteins. This means meat, poultry, fish, eggs, cheese, and milk are complete proteins. Seeds such as soy, black beans, kidney beans, and quinoa contain complete proteins. Plant sources such as legumes, seeds, grains, and vegetables may also contain complete proteins.

What Incomplete Proteins

Incomplete proteins are proteins that lack one or more essential amino acids in correct proportions required by humans and other animals. Generally, most of the proteins obtained from plant sources are incomplete proteins. A combination of two incomplete proteins creates a contemporary protein, which is a complete protein. Incomplete protein sources are shown in figure 2.

Main Difference - Complete vs Incomplete Proteins

Figure 2: Grains

Grains, legumes, nuts, barley, oats, peanuts, wheat, beans, and lentils are sources of incomplete proteins. Grains and legumes, grains and nuts/seeds, and legumes and nuts/seeds are some combinations of incomplete proteins, which may act as a contemporary protein.

Similarities Between Complete and Incomplete Proteins

Both complete and incomplete proteins are important nutrients in the body.
Both complete and incomplete proteins are made up of amino acids.
Both complete and incomplete proteins may contain essential amino acids.
Both complete and incomplete proteins can be included in plants.

Definition

Complete Proteins: Complete proteins are proteins that contain all essential amino acids in the correct ratio for humans.

Incomplete Proteins: Incomplete proteins are proteins that are lacking in one or more essential amino acids in correct proportions as required by humans and other animals.

Essential Amino Acids

Complete Proteins: Complete proteins contain all essential amino acids.

Incomplete Proteins: Incomplete proteins contain some of the essential amino acids.

Sources

Complete Proteins: Animal sources of proteins such as fish meat, poultry, eggs, and dairy products contain complete proteins. Soybeans and quinoa also contain complete proteins.

Incomplete Proteins: Nuts, beans, legumes, and tofu like plant sources contain incomplete proteins.

Conclusion

Complete and incomplete proteins are two types of proteins in our diet. Complete proteins contain all the nine essential amino acids in the same source. But, incomplete proteins do not contain all essential amino acids in the same source. A combination of two or more incomplete proteins together will produce a complete protein in the diet. The main difference between complete and incomplete protein is the supplement of essential amino acids in the diet by each of these proteins.

Reference:

1. Sugar, Jenny. “This Is How to Eat Enough Protein on a Vegetarian Diet.” POPSUGAR Fitness, 2 July 2017, Available here.
2. “INCOMPLETE PROTEINS | COMBINATIONS OF PROTEIN FOODS” Myfit.ca, Available here.

Image Courtesy:

1. “Various grains” By Peggy Greb, USDA ARS (Public Domain) via Commons Wikimedia
2. “2358567” (CC0) via Max Pixel