Amino Acids

Tissue Abundance — Free Amino Acid Pool

Approximate share of the intracellular free amino acid pool in major taurine-rich tissues (heart, skeletal muscle, brain, retina, leukocytes). Plasma proportions differ — glutamine dominates plasma; taurine dominates intracellular compartments.

#	Amino Acid / Compound	% Free Pool
1	Taurine	~50–60%
2	Glutamine	~15–25%
3	Glutamate	~5–10%
4	Alanine	~3–6%
5	Glycine	~2–5%
6	Serine	~1–3%
7	Threonine	~1–3%
8	Lysine	~1–3%
9	Arginine	~1–2%
10	Proline	~1–2%
11	Histidine	<1–2%
12	Asparagine	<1–2%
13	Aspartic Acid	<1–2%
14	Valine	<1%
15	Leucine	<1%
16	Isoleucine	<1%
17	Phenylalanine	<1%
18	Tyrosine	<1%
19	Methionine	<1%
20	Cysteine	<1%
21	Tryptophan	<1%

Bottom line: Taurine is the most abundant free amino-acid-like compound in the human body — a 70-kg adult carries ~70 g of taurine, mostly intracellular. Sources: Ripps & Shen, Mol Vision 2012 (PMC3501277); Lambert et al., Acta Physiol 2015 (DOI). See Taurine and Electrolyte Balance for the underlying biochemistry.

Featured Amino Acids

TAURINE ›

The most abundant free amino-acid-like compound in the body — heart, brain, retina, electrolyte balance, longevity.

GLYCINE ›

Calming inhibitory neurotransmitter, foundational collagen building block, sleep quality and recovery.

GLUTAMINE ›

Primary fuel for gut lining and immune cells; nitrogen carrier; recovery from illness, surgery, intense training.

CYSTEINE ›

Rate-limiting precursor for glutathione (master antioxidant) and for endogenous taurine synthesis.

METHIONINE ›

Universal methyl donor via SAMe; sulfur metabolism; epigenetic regulation; liver detoxification support.

ARGININE ›

Nitric oxide precursor for vascular dilation and blood flow; wound healing; urea cycle nitrogen disposal.

TRYPTOPHAN ›

Precursor to serotonin, melatonin, and NAD+; central to mood regulation, sleep onset, and circadian rhythm.

LEUCINE ›

Most potent BCAA; mTOR activator; primary trigger for muscle protein synthesis after exercise and meals.

LYSINE ›

Essential amino acid; collagen crosslinking, calcium absorption, carnitine precursor for fat metabolism.

THREONINE ›

Essential amino acid; mucin synthesis and gut barrier integrity; collagen and elastin building block.

HISTIDINE ›

Essential amino acid; histamine precursor; carnosine dipeptide in muscle; hemoglobin synthesis.

PHENYLALANINE ›

Essential amino acid; direct precursor to tyrosine and downstream catecholamines; mood and focus.

TYROSINE ›

Precursor to dopamine, norepinephrine, and thyroid hormone (T3/T4); stress resilience and cognitive performance.

Amino acids are the building blocks of proteins and play critical roles in virtually every biological process. They are essential for muscle growth, immune function, neurotransmitter production, hormone synthesis, and tissue repair. Browse the complete guide to all essential and non-essential amino acids below.

Essential Amino Acids

Essential amino acids cannot be synthesized by the human body and must be obtained through diet or supplementation.

Amino Acid	Body Content (g)	Key Roles	Top Food Sources
Leucine	~600 g	Protein synthesis, muscle repair, blood sugar regulation, growth hormone	Whey protein, soybeans, beef, chicken, peanuts
Lysine	~600 g	Collagen formation, calcium absorption, immune support, hormone production	Red meat, fish, dairy, eggs, legumes
Valine	~400 g	Muscle growth, tissue repair, energy production, nervous system function	Soy, cheese, mushrooms, peanuts, whole grains
Threonine	~350 g	Collagen and elastin synthesis, immune function, gut health, liver support	Lean meat, cottage cheese, lentils, sesame seeds
Phenylalanine	~350 g	Dopamine and norepinephrine precursor, mood regulation, pain relief	Soybeans, cheese, nuts, seeds, beef, fish
Isoleucine	~300 g	Muscle metabolism, energy regulation, immune function, hemoglobin synthesis	Eggs, soy, seaweed, turkey, lamb, cheese
Histidine	~200 g	Histamine production, immune response, digestion, sleep-wake cycles	Meat, fish, poultry, nuts, seeds, whole grains
Methionine	~200 g	Detoxification, antioxidant (glutathione), tissue growth, sulfur metabolism	Eggs, fish, sesame seeds, Brazil nuts, meat
Tryptophan	~100 g	Serotonin and melatonin precursor, mood, sleep, appetite regulation	Turkey, chicken, oats, cheese, nuts, seeds
Taurine	~70 g	Heart health, bile salt formation, antioxidant, electrolyte balance, nervous system	Shellfish, dark meat poultry, beef, fish, dairy

Note on Body Content (g): Approximate total grams in a 70-kg adult, combining protein-bound residues and the free amino acid pool. Most essential amino acids are ~99% protein-bound (in muscle, collagen, organ tissue); Taurine is the exception — it has no codon and is not incorporated into proteins, so its ~70 g total is entirely free-pool. By that free-pool metric Taurine dominates (see the "% Free Pool" reference table above), but by absolute mass in the body, Leucine and Lysine come out on top.

Non-Essential Amino Acids

Non-essential amino acids can be synthesized by the body, but supplementation may be beneficial during illness, stress, or intense physical activity.

Amino Acid	Body Content (g)	Key Roles	Top Food Sources
Glycine	~1,000 g	Collagen synthesis, neurotransmitter, sleep quality, creatine production	Bone broth, meat, fish, dairy, legumes, spinach
Glutamic Acid	~800 g	Excitatory neurotransmitter, brain function, gut fuel, detoxification	Tomatoes, cheese, mushrooms, soy sauce, seaweed
Alanine	~700 g	Glucose metabolism, energy production, immune support, muscle fuel	Meat, poultry, fish, eggs, dairy, beans
Proline	~700 g	Collagen formation, joint health, skin elasticity, wound healing	Bone broth, gelatin, meat, dairy, cabbage, eggs
Aspartic Acid	~600 g	Neurotransmitter synthesis, energy (Krebs cycle), hormone regulation	Oysters, avocado, asparagus, molasses, meat
Arginine	~550 g	Nitric oxide production, blood flow, wound healing, immune function	Turkey, pork, pumpkin seeds, soybeans, peanuts
Glutamine	~500 g	Gut lining repair, immune fuel, muscle recovery, nitrogen transport	Beef, eggs, tofu, corn, white rice, milk
Serine	~500 g	Phospholipid synthesis, brain function, immune support, muscle growth	Soybeans, eggs, dairy, peanuts, lentils, meat
Asparagine	~400 g	Nervous system function, protein synthesis, ammonia detoxification	Asparagus, dairy, poultry, eggs, potatoes, nuts
Tyrosine	~300 g	Dopamine, adrenaline, and thyroid hormone precursor, stress response	Cheese, soybeans, beef, lamb, fish, dairy, seeds
Cysteine	~200 g	Glutathione synthesis, detoxification, skin and hair health, antioxidant	Poultry, eggs, dairy, garlic, onions, broccoli

Understanding Amino Acid Classification

The human body requires 20 standard amino acids to build the thousands of proteins it needs. Of these, nine are classified as essential because the body cannot manufacture them — they must come from food. The remaining eleven are non-essential, meaning the body can synthesize them under normal conditions. However, several non-essential amino acids become conditionally essential during periods of illness, trauma, surgery, or intense physical stress, when the body's demand exceeds its production capacity.

A balanced intake of all amino acids — through whole proteins from animal or plant sources, or strategic supplementation — is foundational to optimal health, performance, and longevity.

Back to Home