At the grocery store, gym, or kitchen you’ll notice protein talked about everywhere — on labels, in recipes, and in training plans. Understanding which amino acids your body must get from food helps you choose better meals and spot gaps in your diet.
There are 9 Essential Amino Acids, ranging from Histidine to Valine. For each, you’ll find below the data organized as: One-letter code,Main function & deficiency (15 words max),Top food sources (15 words max),Adult requirement (mg/kg/day), so you can scan functions, foods, and needs — you’ll find below.
How can I get all nine essential amino acids if I eat mostly plants?
You can meet requirements by combining varied plant proteins across the day — legumes, grains, nuts, seeds, and soy together provide complementary profiles; focus on whole foods and a few servings of high-protein plants daily.
Do I need to track each amino acid separately to stay healthy?
For most adults, tracking total protein and eating diverse protein sources is enough; only athletes, those with medical issues, or strict diets usually need precise amino-acid tracking or targeted supplementation.
Essential Amino Acids
| Name | One-letter code | Main function & deficiency (15 words max) | Top food sources (15 words max) | Adult requirement (mg/kg/day) |
|---|---|---|---|---|
| Histidine | H | Nerve cell protection, histamine production. Deficiency is rare; can cause skin lesions, anemia. | Meat, fish, poultry, dairy, eggs, soy, whole grains, nuts, seeds. | 12 |
| Isoleucine | I | Muscle metabolism, hemoglobin formation. Deficiency causes muscle tremors, dizziness, fatigue, and irritability. | Meat, poultry, fish, eggs, dairy, lentils, nuts, seeds, soy products. | 19 |
| Leucine | L | Muscle protein synthesis, growth hormone production. Deficiency leads to muscle wasting and skin lesions. | Meat, poultry, fish, dairy (especially whey/casein), eggs, soy, beans, lentils. | 42 |
| Lysine | K | Protein synthesis, calcium absorption. Deficiency may cause fatigue, nausea, hair loss, poor appetite. | Meat, poultry, fish, eggs, dairy, soybeans, lentils, quinoa, pumpkin seeds. | 38 |
| Methionine | M | Metabolism, detoxification, tissue growth. Deficiency can cause fatty liver, edema, and skin lesions. | Meat, fish, poultry, eggs, dairy, sesame seeds, Brazil nuts, soybeans. | 19 |
| Phenylalanine | F | Neurotransmitter production, protein structure. Deficiency is rare; can cause confusion and memory problems. | Meat, poultry, fish, eggs, dairy, soy products, nuts, seeds, beans. | 33 |
| Threonine | T | Collagen and elastin production, fat metabolism. Deficiency can cause digestive issues and irritability. | Meat, poultry, fish, eggs, dairy, cottage cheese, lentils, sesame seeds. | 20 |
| Tryptophan | W | Serotonin and melatonin precursor. Deficiency may cause sleep issues, depression, and anxiety. | Turkey, chicken, dairy, eggs, oats, bananas, nuts, seeds, tofu. | 5 |
| Valine | V | Muscle growth, energy production. Deficiency can disrupt nervous system function and cause poor growth. | Meat, poultry, fish, dairy, soy products, beans, lentils, peanuts, mushrooms. | 24 |
Images and Descriptions
Histidine
Histidine is crucial for making histamine, a compound vital for immune response, digestion, and sleep cycles. It also helps maintain the protective myelin sheath around nerve cells, ensuring proper nervous system function.
Isoleucine
An important branched-chain amino acid (BCAA), isoleucine is heavily concentrated in muscle tissue. It plays a key role in muscle metabolism, hemoglobin production, and regulating blood sugar and energy levels, especially during exercise.
Leucine
As the primary branched-chain amino acid (BCAA) that stimulates muscle protein synthesis, leucine is a powerhouse for muscle growth and repair. It also aids in regulating blood sugar levels and producing growth hormones.
Lysine
Lysine is a fundamental building block for proteins and is essential for producing carnitine, which converts fatty acids into energy. It also plays a significant role in calcium absorption and the formation of collagen for healthy skin and bones.
Methionine
Methionine is a sulfur-containing amino acid critical for metabolism and the body’s natural detoxification processes. It is also vital for tissue growth, mineral absorption, and is a precursor to other important sulfur-containing compounds.
Phenylalanine
Phenylalanine is a precursor to tyrosine, which is used to create vital neurotransmitters like dopamine and adrenaline. These brain chemicals are crucial for mood, focus, and responding to stress, making this amino acid key for neurological health.
Threonine
Threonine is a principal component of structural proteins like collagen and elastin, which provide strength and elasticity to skin and connective tissues. It also plays a key role in fat metabolism in the liver and supports a healthy immune system.
Tryptophan
Famously known as a precursor to the “feel-good” neurotransmitter serotonin and the sleep hormone melatonin, tryptophan is essential for regulating mood, appetite, and sleep. Its role in brain chemistry makes it vital for mental well-being.
Valine
The third branched-chain amino acid (BCAA), valine is crucial for muscle metabolism, tissue repair, and maintaining nitrogen balance. It also serves as an energy source for muscles during physical activity, supporting endurance and recovery.
