Essential Amino Acids
Amino acids are organic compounds composed mainly of nitrogen, carbon, hydrogen, and oxygen.
Your body needs 20 different amino acids to grow and function properly. While all 20 of these are important for your health, only 9 are classified as essential.
These are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
Although your body can make nonessential amino acids, it cannot make essential amino acids, so you have to get them from your diet.
The best sources of essential amino acids are animal proteins such as meat, eggs, and poultry. However, some plant foods, such as the soy products edamame and tofu, contain all nine essential amino acids. This means they are “complete” sources of protein.
After you eat protein, your body breaks it down into amino acids and then uses them for various processes, such as building muscle and regulating immune function.
Conditionally essential amino acids
Several nonessential amino acids are classified as conditionally essential.
These are essential only under specific circumstances, such as during illness, pregnancy, infancy, or trauma.
For example, arginine is considered nonessential, but your body can’t make as much as you need when you’re healing from a serious injury or fighting certain diseases, such as cancer.
That’s why, in certain situations, people may take argnine supplements to meet their bodies’ needs.
Additionally, certain amino acids, including glycine and arginine, are considered conditionally essential during pregnancy because a pregnant person needs more of these amino acids to support their own health and the health of the fetus.
How many essential amino acids are there?
There are nine essential amino acids, each of which performs a number of important jobs in your body:
- Phenylalanine. Your body turns this amino acid into the neurotransmitters tyrosine, dopamine, epinephrine, and norepinephrine. It plays an integral role in the structure and function of proteins and enzymes and the production of other amino acids.
- Valine. This is one of three branched-chain amino acids (BCAAs) on this list. That means it has a chain branching off from one side of its molecular structure. Valine helps stimulate muscle growth and regeneration and is involved in energy production.
- Threonine. This is a principal part of structural proteins, such as collagen and elastin, which are important components of your skin and connective tissue. It also plays a role in fat metabolism and immune function.
- Tryptophan. Often associated with drowsiness, tryptophan is a precursor to serotonin, a neurotransmitter that regulates your appetite, sleep, and mood.
- Methionine. This amino acid plays an important role in metabolism and detoxification. It’s also necessary for tissue growth and the absorption of zinc and selenium, minerals that are vital to your health .
- Leucine. Like valine, leucine is a BCAA that is critical for protein synthesis and muscle repair. It also helps regulate blood sugar levels, stimulates wound healing, and produces growth hormones.
- Isoleucine. The last of the three BCAAs, isoleucine is involved in muscle metabolism and is heavily concentrated in muscle tissue. It’s also important for immune function, hemoglobin production, and energy regulation.
- Lysine. Lysine plays major roles in protein synthesis, calcium absorption, and the production of hormones and enzymes. It’s also important for energy production, immune function, and the production of collagen and elastin.
- Histidine. Your body uses this amino acid to produce histamine, a neurotransmitter that is vital to immune response, digestion, sexual function, and sleep-wake cycles. It’s critical for maintaining the myelin sheath, a protective barrier that surrounds your nerve cells.
While essential amino acids can be found in a wide array of foods, taking concentrated doses in supplemental form has been linked to several health benefits.
May help with mood
Tryptophan is necessary for the production of serotonin, a chemical that acts as a neurotransmitter in your body.
Serotonin is an essential regulator of mood, sleep, and behaviors.
While low serotonin levels have been linked to depressed mood and sleep disturbances, several studies have shown that taking tryptophan supplements may help reduce symptoms of depression and boost mood.
A review that included 11 high quality studies found that taking 0.14–3 grams of tryptophan per day could help decrease anxiety and increase positive mood in healthy people.
May improve exercise performance and recovery
Many people take valine, leucine, and isoleucine, the three essential BCAAs, to alleviate fatigue, improve athletic performance, and stimulate muscle recovery after exercise.
In a small 2017 study, resistance-trained athletes took BCAAs at a dose of 0.039 grams per pound (0.087 grams per kg) of body weight, with a 2:1:1 ratio of leucine, isoleucine, and valine.
Those who took the BCAAs showed improved performance and muscle recovery and decreased muscle soreness compared with those who took a placebo.
A review of eight studies found that taking BCAAs was superior to rest for promoting muscle recovery and reducing soreness after exhaustive exercise.
What’s more, another review that included nine studies found that taking BCAAs helped reduce muscle damage and soreness after resistance exercise in active men.
Taking BCAAs has also been shown to reduce the rating of perceived exertion — how intensely a person feels they are working during exercise — in people performing high intensity exercise.
May be helpful for wound healing and surgery
Taking amino acid supplements may be helpful for people who are healing after surgery.
A study in 243 people with pelvis or long bone fractures found that those who took conditionally essential amino acids for 2 weeks after surgery had lower rates of death and medical complications than those who received standard nutrition.
A review of 20 studies looking at the effects of taking BCAAs in people with cancer undergoing surgery found that those who took BCAAs around the time of surgery had reduced postoperative complications from infections and fluid accumulation in the abdomen.
What’s more, according to results from one study, taking essential amino acid supplements may help reduce loss of muscle volume in older adults recovering from knee replacement surgery.