Essential amino acids are organic molecules your body requires to operate effectively. They must be obtained from certain foods.
Amino acids, commonly called the building blocks of proteins, are compounds that carry out numerous vital functions in your body.
You need them for key processes like making proteins, hormones, and neurotransmitters.
These amino acids are abundant in protein-rich foods such as meat, fish, and soy products.
Some individuals also use specific amino acids as supplements to naturally support athletic performance or to help mood.
They’re grouped as essential, conditionally essential, or nonessential depending on various circumstances.
This article covers the essentials about essential amino acids — how they work, foods high in them, and possible advantages of supplementation.
What are essential amino acids?
Amino acids are organic compounds composed primarily of nitrogen, carbon, hydrogen, and oxygen.
Your body depends on 20 distinct amino acids for growth and normal function. While all 20 are important, only nine are considered essential.
These include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
Although your body can synthesize nonessential amino acids, it cannot produce essential ones, so they must come from your diet.
The richest sources of essential amino acids are animal-derived proteins like meat, eggs, and poultry. Some plant foods, for instance soy products such as edamame and tofu, also provide all nine essential amino acids, making them “complete” proteins.
When you consume protein, your body breaks it down into amino acids and uses them for tasks such as muscle building and supporting immune function.
Conditionally essential amino acids
Certain nonessential amino acids become conditionally essential under special circumstances.
These are required only in specific situations, such as illness, pregnancy, infancy, or following trauma.
For example, arginine is generally nonessential, but during recovery from major injury or while battling some diseases (including cancer), your body may be unable to make enough.
Consequently, people in those situations might take arginine supplements to meet increased needs.
Likewise, some amino acids like glycine and arginine are considered conditionally essential during pregnancy because pregnant individuals need extra amounts to support both their own health and fetal development.
For a quick visual summary of the roles of essential amino acids, see the image below.
As shown, essential amino acids are central to many critical bodily functions.
While they’re best known for their role in muscle growth and repair, your body relies on them for much more.
Deficiencies in essential amino acids can negatively affect multiple systems, including the nervous, reproductive, immune, and digestive systems.
Individual amino acid needs vary by life stage, chronic conditions, and acute health events like infections or surgery.
Nevertheless, most people obtain sufficient amounts through their regular diet.
How many essential amino acids are there?
There are nine essential amino acids, each carrying out important roles in the body:
- Phenylalanine: This amino acid is converted into neurotransmitters such as tyrosine, dopamine, epinephrine, and norepinephrine. It contributes to protein and enzyme structure and the production of other amino acids.
- Valine: One of three branched-chain amino acids (BCAAs), valine has a side branch in its molecular structure. It supports muscle growth and repair and participates in energy production.
- Threonine: A key component of structural proteins like collagen and elastin, threonine is important for skin and connective tissues and also contributes to fat metabolism and immune health.
- Tryptophan: Often linked with sleepiness, tryptophan is a precursor to serotonin, a neurotransmitter that influences appetite, sleep, and mood.
- Methionine: This amino acid is involved in metabolism and detox processes. It’s also essential for tissue growth and for absorbing minerals like zinc and selenium.
- Leucine: Another BCAA, leucine is vital for protein synthesis and muscle repair. It also helps regulate blood sugar, supports wound healing, and promotes growth hormone production.
- Isoleucine: The third BCAA, isoleucine is important for muscle metabolism and is highly present in muscle tissue. It also supports immune function, hemoglobin formation, and energy balance.
- Lysine: Lysine is crucial for protein synthesis, calcium absorption, and the production of hormones and enzymes. It also aids energy production, immune health, and the formation of collagen and elastin.
- Histidine: Your body uses histidine to make histamine, a compound involved in immune responses, digestion, sexual function, and sleep-wake regulation. It also helps maintain the myelin sheath that protects nerve cells.
As shown, essential amino acids are central to many critical bodily functions.
While they’re best known for their role in muscle growth and repair, your body relies on them for much more.
Deficiencies in essential amino acids can negatively affect multiple systems, including the nervous, reproductive, immune, and digestive systems.
Individual amino acid needs vary by life stage, chronic conditions, and acute health events like infections or surgery.
Nevertheless, most people obtain sufficient amounts through their regular diet.
Health benefits of taking essential amino acid supplements
Although essential amino acids are present in many foods, concentrated supplements have been associated with several potential health benefits.
May help with mood
Tryptophan is required for producing serotonin, a neurotransmitter that influences mood and sleep.
Serotonin plays a key role in regulating mood, sleep, and behavior.
Low serotonin levels have been associated with depressive symptoms and sleep problems, and multiple studies indicate tryptophan supplementation may help reduce depression symptoms and improve mood.
A review of 11 high-quality trials found that taking 0.14–3 grams of tryptophan daily could lower anxiety and enhance positive mood in generally healthy individuals.
May improve exercise performance and recovery
Many athletes use the BCAAs valine, leucine, and isoleucine to fight fatigue, boost performance, and speed muscle recovery after workouts.
A 2017 review included a study where resistance-trained athletes consumed BCAAs at 0.039 g per pound (0.087 g per kilogram) of body weight in a 2:1:1 leucine:isoleucine:valine ratio.
Those taking BCAAs experienced better performance, enhanced muscle recovery, and less muscle soreness compared with a placebo group.
The review also concluded BCAAs were more effective than rest alone for promoting muscle recovery and decreasing soreness after exhaustive exercise.
Additionally, another review of nine studies found BCAA supplementation reduced muscle damage and soreness after resistance training in active men.
Supplementing with BCAAs has also been shown to lower perceived exertion during high-intensity exercise.
May be helpful for wound healing and surgery
Amino acid supplements can be beneficial for people recovering from surgery.
A study of 243 patients with pelvic or long bone fractures found those who took conditionally essential amino acids for two weeks after surgery had fewer deaths and medical complications than those receiving standard nutrition.
A review of 20 studies assessing BCAA use in surgical cancer patients reported fewer postoperative complications like infections and abdominal fluid accumulation among those who took BCAAs around surgery.
Moreover, one study indicates essential amino acid supplements may help limit muscle loss in older adults recovering from knee replacement surgery.
Food sources and recommended intake
Because the body cannot make essential amino acids, it’s important to obtain them from food.
Many everyday foods supply these amino acids, so meeting daily requirements is typically straightforward.
Below are adult daily requirements per 2.2 lb (1 kg) of body weight, according to the World Health Organization:
- Histidine: 10 milligrams (mg)
- Isoleucine: 20 mg
- Leucine: 39 mg
- Lysine: 30 mg
- Methionine: 10.4 mg
- Phenylalanine combined with the nonessential amino acid tyrosine: 25 mg
- Threonine: 15 mg
- Tryptophan: 4 mg
- Valine: 26 mg
To calculate your daily needs, multiply these values by your weight in kilograms. For instance, a 60 kg (132 lb) person should aim for about 1,200 mg (1.2 g) of isoleucine daily.
Meeting these targets is easy with most diets, so tracking individual amino acids is rarely necessary.
For example, a 174-g serving of braised chicken breast provides 55.9 g of complete protein, which more than covers the amounts listed above.
Food sources
Foods containing all nine essential amino acids are called complete proteins.
Common complete protein foods include:
- meat
- seafood
- poultry
- eggs
- dairy products
Soy and pea protein are plant-based complete protein sources.
Other plant proteins such as beans, nuts, and some grains are considered incomplete because they lack one or more essentials.
Still, if you follow a plant-based diet, you can meet your essential amino acid needs by combining a variety of plant proteins throughout the day.
For example, consuming a mix of beans, nuts, seeds, whole grains, and vegetables will help ensure adequate intake even without animal products.
How to supplement with essential amino acids
Most people obtain enough essential amino acids from food.
That said, supplementation can be useful in certain cases — athletes often use them to support performance and recovery.
One review of 10 quality studies found BCAA doses up to 115.6 mg per lb (255 mg per kg) per day may reduce delayed-onset muscle soreness in trained individuals after exercise.
Some people opt for single amino acid supplements rather than blends to target specific goals, such as mood enhancement.
A review of 11 high-quality studies showed taking 0.14–3 g of tryptophan per day could improve mood in healthy subjects.
As these examples show, effective dosing depends on which amino acid is used and the intended outcome.
Amino acid supplements are generally safe for most individuals, though they’re usually unnecessary if dietary protein intake is adequate.
Still, supplements may benefit specific populations. If you’re considering essential amino acid supplements, consult a healthcare professional familiar with dietary supplements, such as your physician or a registered dietitian.
They can advise on appropriate doses, optimal timing, and reputable brands that use third-party testing.
The bottom line
Nine amino acids are essential — histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine — and must be obtained through food.
They support many body functions, including protein synthesis, tissue repair, and nutrient absorption.
Some may aid in preserving muscle, enhancing recovery after surgery, and improving mood, sleep, and athletic performance.
These important nutrients are present in many animal- and plant-based foods, so most people can meet their needs with a balanced diet. Supplements are an option when necessary.
Just one thing
Try this today: If you’re worried you’re not getting enough essential amino acids, try increasing your protein intake.
Adding foods such as eggs, fish, and Greek yogurt to meals and snacks can help you reach your amino acid targets.
You can read more about plant-based protein options in the linked article.
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