Amino acids are molecules that are the building blocks of proteins. There are 20 different amino acids found in proteins, each of which has its own unique characteristics. Your body uses amino acids to make proteins and each amino acid plays a vital role in the body’s metabolism and are essential for normal cell and tissue growth, development, and functioning. They are also important for the production of enzymes, hormones, neurotransmitters, and energy production.
This article will discuss what amino acids are, how to test amino acid levels, and the daily recommended required amount for proper health and function.
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What are Amino Acids?
Proteins are built from fundamental molecules called amino acids. An amino acid is a small organic molecule with a central carbon atom connected to an amino group, carboxyl group, hydrogen atom, and a unique side chain.
The 20 amino acids each have unique side chains (R groups) that determine their chemical properties. For example, some have polar R groups that dissolve in water, while others are hydrophobic and avoid water. Some R chains can also be reactive, acidic, or basic. The specific combination and interaction of these different amino acids result in each protein having a distinct 3D shape and performing particular biological functions. When multiple amino acids bond via peptide bonds, they form a long chain, constituting a protein's primary structure.
Thus, proteins are constituted by one or more chains of amino acids, known as polypeptides, the order of which is specified by a gene. The body physiologically produces some amino acids. However, other amino acids, called essential amino acids, must be obtained through dietary means as they cannot be synthesized.
What Are The Different Types Of Amino Acids?
There are 20 amino acids with different chemical and physical properties; in alphabetical order, they are:
- Alanine
- Arginine
- Asparagine
- Aspartic Acid
- Cysteine
- Glutamic acid
- Glutamine
- Glycine
- Histidine
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Proline
- Serine
- Threonine
- Tryptophan
- Tyrosine
- Valine
Despite their chemical and physical diversity, amino acids can be grouped into three categories: Essential, Nonessential, and Conditional.
Essential Amino Acids
Nine amino acids - histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine - cannot be synthesized by mammals and must be obtained through diet and are therefore called "essential amino acids." Under specific circumstances, like liver damage, non-essential amino acids may become essential.
A complete protein, which contains all nine essential amino acids, is typically obtained from animal-based sources of nutrition, such as meat and dairy products, but can also be found in soy. Essential amino acids are also obtainable from incomplete proteins, which are often plant-based foods.
Nonessential Amino Acids
Nonessential amino acids, even if not obtained from food, can be produced by the body. These include tyrosine, serine, alanine, arginine, aspartic acid, cysteine, asparagine, glutamic acid, glutamine, glycine, and proline.
Conditional Amino Acids
Conditional amino acids are usually not essential but become so under certain conditions such as illness or stress. These include arginine, cysteine, glutamine, tyrosine, glycine, proline, and serine.
What is Amino Acids' Role in The Body?
Amino acids have crucial roles in the body, such as:
- Affecting muscle and connective tissue growth and assisting in the formation of skin
- Improving the tissue strength
- Assisting in normal digestion
- Supplying energy for the body
- Helping to produce hormones in the body
- Maintaining healthy hair
Functional amino acids (FAAs) have emerged from a growing body of literature. FAAs are those amino acids that regulate crucial metabolic pathways to enhance health, growth, reproduction, and other vital processes in organisms and include essential and non-essential amino acids.
FAAs play a dual role in the body by building proteins and regulating metabolic pathways that impact health, survival, growth, and development. FAAs are necessary for muscle growth, development, and repair, as well as collagen and elasticity production, protein synthesis, energy generation from carbohydrates, and regulation of insulin secretion to maintain healthy blood sugar levels. FAAs are also critical for immune function by supporting antibody production and normal brain function. A deficiency in any FAA impairs protein synthesis and overall body balance, leading to serious health issues such as muscle loss, stunted growth, weakened immune system, skin problems, and metabolic and neurological disorders.
How to Test Amino Acids
Amino acid testing helps identify dietary protein adequacy, amino acid balance, protein intolerance, and other disorders related to amino acid metabolism. Plasma is traditionally used to assess the status of essential amino acids, while urine analysis provides more information regarding amino acid wasting and aberrant metabolism.
Different laboratory tests can be performed to analyze the amino acid balance in the body:
Amino Acids Panel: this blood test measures eight amino acids to evaluate nutritional deficiencies and abnormalities in patients.
Plasma Amino Acids: this type of nutritional testing measures what is being transported at the time of sampling. The specimen should be collected after an overnight fast to reduce the influence of dietary protein. Abnormalities are deduced by comparison of measured levels with an established reference range.
Urine Amino Acids (FMV): this profile helps diagnose various health issues such as dietary protein sufficiency, amino acid balance, gastrointestinal problems, vitamin and mineral deficiencies, kidney and liver dysfunction, and more. This test is more informative than plasma analysis when identifying amino acid wastage and unusual metabolism linked to co-factor deficiencies. The sample for this test is usually collected in the first-morning void but can also be obtained through a 24-hour collection.
How to Make Sure You are Getting Enough Amino Acids
It is not necessary to consume amino acids in every meal, but it's essential to ensure a balanced intake throughout the day.
The recommended daily allowance (RDA), calculated based on every 2.2 pounds of body weight, for each of the essential amino acids is:
- Histidine: 14 mg
- Isoleucine: 19 mg
- Leucine: 42 mg
- Lysine: 38 mg
- Methionine: 19 mg
- Phenylalanine: 33 mg
- Threonine: 20 mg
- Tryptophan: 5 mg
- Valine: 24 mg
Amino acids can be found in various foods, with animal proteins such as beef, poultry, and eggs being the best sources due to their high absorption and utilization by the body. Foods containing the nine essential amino acids, such as beef, poultry, fish, eggs, dairy, soy, quinoa, and buckwheat, are called complete proteins. Incomplete proteins, like nuts, seeds, beans, and some grains, contain some but not all of the essential amino acids.
Vegetarians and vegans should incorporate multiple sources of incomplete proteins to ensure a balanced intake of all essential amino acids. While a healthy, balanced diet provides all the essential amino acids the body needs, some individuals may take amino acid supplements for improved brain function affecting sleep and mood or athletic performance. Amino acid supplementation should only be taken after consulting a healthcare provider.
Summary
Amino acids play crucial roles in human health, including the building and repairing of tissues, hormone and enzyme production, and maintaining the balance of body fluids. They are also the building blocks of proteins, which are essential components of muscles, bones, skin, and other tissues.
Testing the levels of amino acids in adults is important to assess overall nutritional status and identify any deficiencies that may affect health. Imbalances or deficiencies in specific amino acids can lead to several health disorders, such as poor immune function, slowed growth and repair of tissues, decreased muscle mass, and increased risk of chronic diseases. Testing can also help detect and diagnose underlying medical conditions affecting amino acid metabolism, such as liver or kidney diseases.
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