What Are Amino Acids-and Why Do They Matter for Hair Growth?

About 90% of each hair strand is made of keratin, a tough, insoluble protein built from 18 different amino acids. One of the most important is cysteine, which is rich in sulfur. Sulfur gives keratin its strong, flexible structure — meaning when your hair cells have enough cysteine, your strands become stronger, more elastic, and more resilient. Stronger hair breaks less, which allows it to grow longer, thicker, and faster.

Essential vs. Nonessential Amino Acids

There are hundreds of amino acids in nature, but the human body only uses about 20 to build all the proteins we need. These fall into two categories:

Nine Essential Amino Acids

These cannot be made or stored by the body — we must get them through food.

They include:

   •   Phenylalanine

   •   Valine

   •   Tryptophan

   •   Threonine

   •   Isoleucine

   •   Methionine

   •   Histidine

   •   Leucine

   •   Lysine

Foods containing all nine are called complete proteins:

Beef, poultry, fish, eggs, dairy, soy, quinoa, and buckwheat.

Foods with only some essential amino acids are incomplete proteins, such as nuts, seeds, beans, and certain grains.

Eleven Nonessential Amino Acids

These can be produced by the body when needed. They include:

Alanine, Arginine, Asparagine, Aspartic Acid, Cysteine, Glutamic Acid, Glutamine, Glycine, Proline, Serine, and Tyrosine.

How Amino Acids Support Healthy Hair Growth

When you eat a balanced diet with enough protein and complex carbohydrates, your body has the building blocks it needs for:

   •   Tissue repair

   •   Immune function

   •   Red blood cell production

   •   Hormone synthesis

All of these processes support the hair follicle and ensure your hair cells can produce strong, healthy strands.