What are amino acids?
Amino acids are the building blocks of protein. Proteins are long chains of amino acids. Your body has thousands of different proteins that each have important jobs. Each protein has its own sequence of amino acids. The sequence makes the protein take different shapes and have different functions in your body.
You can think of amino acids like the letters of the alphabet. When you combine letters in various ways, you make different words. The same goes for amino acids — when you combine them in various ways, you make different proteins.
What are the different types of amino acids?
Your body needs 20 different kinds of amino acids to function correctly. These 20 amino acids combine in different ways to make proteins in your body.
Your body makes hundreds of amino acids, but it can’t make nine of the amino acids you need. These are called essential amino acids. You must get them from the food you eat. The nine essential amino acids are:
- Histidine: Histidine helps make a brain chemical (neurotransmitter) called histamine. Histamine plays an important role in your body’s immune function, digestion, sleep and sexual function.
- Isoleucine: Isoleucine is involved with your body’s muscle metabolism and immune function. It also helps your body make hemoglobin and regulate energy.
- Leucine: Leucine helps your body make protein and growth hormones. It also helps grow and repair muscle tissue, heal wounds and regulate blood sugar levels.
- Lysine: Lysine is involved in the production of hormones and energy. It’s also important for calcium and immune function.
- Methionine: Methionine helps with your body’s tissue growth, metabolism and detoxification. Methionine also helps with the absorption of essential minerals, including zinc and selenium.
- Phenylalanine: Phenylalanine is needed for the production of your brain’s chemical messengers, including dopamine, epinephrine and norepinephrine. It’s also important for the production of other amino acids.
- Threonine: Threonine plays an important role in collagen and elastin. These proteins provide structure to your skin and connective tissue. They also help with forming blood clots, which help prevent bleeding. Threonine plays an important role in fat metabolism and your immune function, too.
- Tryptophan: Tryptophan helps maintain your body’s correct nitrogen balance. It also helps make a brain chemical (neurotransmitter) called serotonin. Serotonin regulates your mood, appetite and sleep.
- Valine: Valine is involved in muscle growth, tissue regeneration and making energy.
Your body produces the rest of the 11 amino acids you need. These are called nonessential amino acids. The nonessential amino acids are alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine and tyrosine.
Some nonessential amino acids are classified as conditional. This means they’re only considered essential when you’re ill or stressed. Conditional amino acids include arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline and serine.
What is the structure of an amino acid?
An amino acid is an organic chemical. Organic chemicals contain carbon-hydrogen bonds. All amino acids have the same basic structure. Each molecule has a central carbon atom linked together with a basic amino group, a carboxylic acid group, a hydrogen atom and an R-group, or side-chain group. The R-group is what sets the amino acids apart. The R-group determines each amino acid’s chemical nature. The chemical nature controls how it’ll interact with other amino acids and its environment.
The amino acids link together with peptide bonds and become proteins. Then, the forces of other amino acids and the effects of their R-groups fold the protein into specific three-dimensional shapes.
What do amino acids do?
Your body uses amino acids to make proteins. The different types of amino acids and the way they’re put together determine the function of each protein. So, amino acids are involved in many important roles in your body. Amino acids help:
- Break down food.
- Grow and repair body tissue.
- Make hormones and brain chemicals (neurotransmitters).
- Provide an energy source.
- Maintain healthy skin, hair and nails.
- Build muscle.
- Boost your immune system.
- Sustain a normal digestive system.
How many amino acids do I need?
You don’t need to eat foods with amino acids at every meal, but it’s important to get a balance of them throughout your day. The recommended daily allowance for every 2.2 pounds of body weight for each of the essential amino acids are:
- Histidine: 14 milligrams
- Isoleucine: 19 milligrams
- Leucine: 42 milligrams
- Lysine: 38 milligrams
- Methionine: 19 milligrams
- Phenylalanine: 33 milligrams
- Threonine: 20 milligrams
- Tryptophan: 5 milligrams
- Valine: 24 milligrams
What foods contain amino acids?
Essential amino acids can be found in many different foods. The best sources of amino acids are found in animal proteins such as beef, poultry and eggs. Animal proteins are the most easily absorbed and used by your body.
Foods that contain some but not all the essential amino acids are called incomplete proteins. These foods include nuts, seeds, beans and some grains. If you follow a vegetarian or vegan diet, you need to include several types of incomplete proteins in order to ensure you’re consuming all nine essential amino acids.
Should I take amino acid supplements?
You can usually get all the essential amino acids your body needs by eating a healthy, balanced diet. Some people take amino acid supplements to get better sleep, improve their mood and enhance athletic performance. But the U.S. Food and Drug Administration (FDA) has not approved these supplements. You should speak with your healthcare provider before starting any supplements, including amino acid supplements.
A note from Cleveland Clinic
Amino acids are the building blocks of proteins. They are the molecules that all living things need to make protein, and you need 20 of them to help your body function properly. Your body makes 11 of the necessary amino acids. The good news is you don’t have to do anything special to get the remaining nine amino acids your body needs. You just need to eat a balanced diet. Focus on complete proteins — foods that contain all nine essential amino acids, such as meat, eggs and dairy. Incomplete proteins such as nuts and beans are good, too. Talk to your healthcare provider if you need help or suggestions on getting enough amino acids in your diet.
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy