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:

1. 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 (7).
2. 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 (8).
3. 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 (9).
4. Tryptophan: Often associated with drowsiness, tryptophan is a precursor to serotonin, a neurotransmitter that regulates your appetite, sleep, and mood (10).
5. 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 (11).
6. 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 (12).
7. 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 (13).
8. 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 collagen and elastin production (14).
9. 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 (15).

As you can see, essential amino acids are at the core of many vital processes.

Although amino acids are most recognized for their role in muscle development and repair, your body depends on them for so much more.

That’s why essential amino acid deficiencies can negatively affect your entire body, including your nervous, reproductive, immune, and digestive systems.

People can have different amino acid needs based on stage of life, chronic illness, and acute health issues such as an infection or a surgery.

However, most people get all the amino acids they need through their diet.