Essential Amino Acids | Fitness, Health & Exercise Glossary

What Are the 8 Essential Amino Acids and What Are Their Benefits?

Definition of Essential Amino Acids

Essential Amino Acids (also known as Indispensible Amino Acids) are amino acids that cannot be synthesized by the body, and thus must be supplied by diet. 

Essential Amino Acids, while required by the human body to support life, are not called “essential”  because they are more important than other amino acids, but instead because they cannot be produced by the body. In other words, they must be obtained through food sources since the body cannot produce them itself.

Non-essential amino acids are those that are synthesized by the body and do not require dietary supplementation.

List of Essential Amino Acids

In adults, there are eight amino acids that have traditionally been considered essential:

• Phenyalanine
• Valine
• Threonine
• Tryptophan
• Isoleucine
• Methionine
• Leucine
• Lysine

Histidine has recently been discovered to not be synthesized in adults, which raises the list of 9 essential amino acids in adults.

In infants or growing children, the list grows to 12 essential amino acids, including:

• Cysteine
• Tyrosine
• Histidine
• Arginine

Benefits of Essential Amino Acids

Amino acids play a central role as the building block of protein, as well as intermediaries in metabolism. 

The 20 amino acids found in protein facilitate everything from catalyzing most reactions in living cells to controlling cellular activity, including the creation and preservation of muscle.

There are 20 amino acids that make up critical proteins in the body, and depending on age and certain conditions, the body can produce 10-12 of the necessary amino acids independent of diet.

However, a deficiency in even one of the eight essential amino acids (or ten essential amino acids, in the case of infants or growing children) can cause degradation in the body’s proteins, resulting in muscle loss or developmental defects.

Essential Amino Acids and Complete Proteins

Foods that contain all 8 essential amino acids are known as “complete proteins.”  

Animal-based sources of food such as meat (beef, lamb, bison), poultry, eggs, dairy and fish/seafood are considered sources of complete proteins, along with a small number of plant-sources of protein like quinoa, buckweat, hemp and soya.

Most grains, legumes, pulses and vegetables contain some of the essential amino acids, but not all, qualifying them for the moniker “incomplete proteins.”

This means that vegetarians or vegans need to eat a wide variety of plant-based proteins across the day, or combine complementary proteins (for example beans and rice or wheat and corn), in order to ensure that they are consuming all essential amino acids in the right proportions to ensure proper health.

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Category: Fitness, Health & Exercise Glossary