Amino acids are known as the “building blocks of proteins.” This is because amino acids are connected together to form proteins. It uses the amino acids in different combinations for different things. The order in which they join determines the shape and function of the protein they form.
Amino acids come primarily from foods that contain protein. These include meat, fish, eggs, dairy, beans, lentils, soya, nuts and seeds. When protein is digested , it is broken down to amino acids . The body then takes them up and uses them.
What are amino acids?
There are 20 amino acids commonly used by the body to make proteins. Each amino acid has a similar basic structure, but they are not all the same.
A part called the side chain makes each amino acid different. The amino acid itself has its own chemical nature. This difference influences the behaviour of amino acids when they are joined together.
Amino acids do more than help make proteins. Some are also used to produce hormones, enzymes and chemical messengers. They can also be used as a source of energy when needed.
Essential amino acids
The body cannot make nine of the amino acids in sufficient amounts. These are known as essential amino acids because they need to come from your diet.
The nine essential amino acids are:
- Histidine
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Threonine
- Tryptophan
- Valine
Foods such as meat, fish, eggs and dairy products contain all nine essential amino acids. Some plant foods, including soya, can also provide all nine.
This does not mean that you need to eat animal products to get essential amino acids. A varied plant-based diet can provide them too. Beans, lentils, peas, nuts, seeds, grains and soya foods can all contribute to your protein intake.
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Non-essential amino acids
The body can make some amino acids itself. These are called non-essential amino acids.
The term can be confusing because it implies these amino acids are important. They are still needed by the body. The difference is that you normally do not have to obtain them directly from food.
Alanine, aspartic acid and glutamic acid are examples of non-essential amino acids.
There are also conditionally essential amino acids. The body can usually make these, but there may be times when it cannot produce enough. This can happen during illness, injury, periods of rapid growth or other forms of physical stress.
What do amino acids do?
Amino acids have many roles in the body. Their main job is to help make proteins.
Proteins are needed to build and maintain muscles, skin, connective tissue and organs. They are also used to make enzymes. Enzymes help control chemical reactions in the body.
Some amino acids are involved in making hormones and neurotransmitters. Neurotransmitters are chemical messengers that allow nerve cells to communicate.
For example, tryptophan is used in the production of serotonin and melatonin. Tyrosine is involved in making thyroid hormones and other important substances.
Amino acids can also be broken down to provide energy. However, their main role is to support protein production and other important processes.
Amino acids and exercise
Amino acids are often mentioned in relation to exercise and muscle growth.
When you exercise, particularly during resistance training, your muscles experience stress. The body then works to repair and adapt to that stress. Amino acids from dietary protein provide the materials needed to make new muscle proteins.
Leucine is one amino acid that has received particular attention. It plays a role in stimulating muscle protein synthesis, which is the process of making new muscle protein.
You may also hear about BCAAs, or branched-chain amino acids. These are leucine, isoleucine and valine.
BCAA supplements are commonly marketed to people who exercise. However, getting enough complete protein is generally more important than taking BCAAs on their own. Complete protein sources provide a wider range of amino acids.
Which foods contain amino acids?
Any food that contains protein will provide amino acids.
Beneficial sources include meat, poultry, fish, eggs and dairy products. Plant foods can also provide useful amounts of protein.
Examples include:
- Lentils
- Chickpeas
- Beans
- Peas
- Tofu and soya
- Nuts
- Seeds
- Wholegrains
Different foods contain different amounts of individual amino acids. Eating a varied diet can help you get a good range.
You do not need to combine specific foods at every meal. What matters more is getting enough protein and a good variety of foods across your overall diet.
Do you need amino acid supplements?
For most of us, a well-balanced diet that provides adequate protein will supply the amino acids we need.
Amino acid supplements are widely marketed for muscle growth, exercise performance and recovery. But taking extra amino acids does not automatically translate into extra health benefits.
Overall your diet is more important than one specific amino acid in general.
Supplements also may not be right for everyone. Some may interact with medicines or cause problems in some health conditions. If you are considering taking a high-dose amino acid supplement, talk to a doctor, chemist or registered dietitian first.
Why are amino acids important?
Amino acids are essential parts of human nutrition. They help the body make proteins and support many everyday functions.
Some must come from food, while others can normally be made by the body. During illness, injury or periods of increased demand, the body’s needs can change.
In simple terms, amino acids are the raw materials the body uses to make proteins and several other important substances. They come from the foods we eat and are constantly being used as the body grows, repairs tissues and replaces old proteins.
Although the term may sound complicated, amino acids are simply a basic part of how the body acquires the materials it needs to function.
Research Use Only. This glossary explains terminology used in published research. It is not medical advice and does not describe any product for human or animal use.