Amino Acids for Muscle Growth

Key Takeaways

• Amino acids are the fundamental building blocks of muscle. Your body needs all nine essential amino acids from food to repair and build new muscle.
• Protein quality and quantity matter more than timing. So, aim for 1.4 to 2.0 g/kg/d with at least 20g of high-quality complete protein when you eat.
• Whole food “high-quality” proteins beat isolated amino acid supplements; complete protein sources have all EAA in proper ratios.

Amino acids are what muscle is made of. The basic units of muscle are just chains of these tiny molecules linked together. When these amino acid chains get long enough and start to fold up in different shapes, that's called a protein.

The body uses these proteins to repair old muscle and build new muscle. Think of amino acids as the bricks in your muscle-building house. Without enough bricks, no matter how skilled the builders are or how hard they work, you can't build a home. Likewise, without enough amino acids, your muscles can’t grow.

When you eat protein, whether it’s from chicken, peas, yoghurt or fish, your body breaks those proteins back down into amino acids. Then, your cells rebuild new proteins from the amino acids that are used to repair and grow muscle. Plants absorb nitrogen from the soil and make amino acids. Animals eat plants and convert them into muscle. Humans then eat the animals (or plants), break these proteins down into amino acids, and then rebuild them.

Just twenty amino acids are used to make protein. Nine of these are what’s called “essential" amino acids (EAA), as your body cannot make them, so you have to get them from your diet. The other 11 are non-essential amino acids (NEAA), which your body can produce as needed. Both are important. However, the EAA are a bit more important as far as muscle growth is concerned.

The building blocks of muscle

Amino acids are also the main source of nitrogen in the body, with each amino acid containing at least one nitrogen atom. Consequently, scientists have used a technique known as “nitrogen balance” to estimate the amount of protein you need and to also assess whether the body is gaining muscle (positive “nitrogen balance”) or losing muscle (negative “nitrogen balance”).

The process of building muscle from amino acids is called “Muscle Protein Synthesis” (MPS) — this biological process is the engine of muscle growth. To trigger it, you require both a "stimulus" (like exercise, nutrients, or hormones) and an adequate supply of amino acids, especially EAAs, with leucine playing a key role.

While carbohydrates and fats get some attention, when it comes to muscle growth, protein and amino acids are the most important things. Getting enough high-quality protein day-to-day is one of the most important things you can do to support strength, recovery, and performance. However, not all amino acids, or even all EAA, are equal in promoting muscle growth.

Amino acids and their function

These are the physiological roles of different amino acids outside of muscle repair and growth. The nine Essential amino acids are bolded.

• Alanine: Energy, brain health, immune health, detoxification
• Arginine: Immune health, circulation, detoxification
• Asparagine: Gene control, immune health, nerve health
• Aspartic acid: Energy, brain health, gene building, detoxification
• Cysteine: Protein structure, cell protection, and cell communication
• Glutamic acid: Energy, brain health, immune health, detoxification
• Glutamine: Immune health, energy, inflammation, detoxification
• Glycine: Nerve health, function, gene building, oxygen transport
• Histidine: Oxygen transport, oxidative stress, immune health, gut health
• Isoleucine: Energy, amino acid building
• Leucine: Energy, Gene Expression, immune health
• Lysine: Immune health, collagen support
• Methionine: Heart health, gene regulation, energy, antioxidant
• Phenylalanine: Brain health, circulation
• Proline: Collagen, cell maintenance, immune health, stress response
• Serine: Gene building, energy, and brain health
• Theonine: Gut Health, immune health, energy
• Tryptophan: Mood, inflammation control, immune health, energy
• Tyrosine: Brain health, immune health, energy, and antioxidant 
• Valine: Muscle energy, amino acid building

What amino acids matter

All nine of the EAA must come from your diet in adequate amounts. However, among these, three are called “Branched-Chain Amino Acids” (BCAA) — leucine, isoleucine, and valine.

Out of the three BCAAs, leucine is known to be particularly important for “flipping the switch”, turning on MPS. That’s why high-quality protein sources like eggs, dairy, and meat are generally considered “complete” proteins, as they deliver all nine EAA in the right amounts. Whereas, if one or more of the EAA are missing, or not provided in adequate amounts, the protein source is typically considered “incomplete”. Animal proteins are complete proteins with balanced profiles. Whereas, plant proteins usually have 1 or more EAA missing. Meaning that they need to be obtained from elsewhere.

Is amino acid timing important?

Your body is continuously breaking down and rebuilding muscle, about 1–2% every day. This “turnover” of muscle tissue is what allows it to adapt to new challenges, like when you start a weightlifting program. Because if your muscles weren't able to tear down and rebuild themselves, the adaptation process would be much slower.

Therefore, it is generally advised to eat several high-quality protein-rich meals or supplements spaced throughout the day to support muscle building. Timing is a well-debated topic, but consuming enough protein at each meal (with some protein at snacks too) is an effective strategy.

The general recommendation for the amount of protein you eat is about 0.8 g/kg/day minimum for most people, 1.4-2.0 g/kg/day for those who are training for hypertrophy, and possibly higher for high-performance athletes who are training a lot. Aim for at least 20 g of high-quality “complete” protein per meal to maximally stimulate muscle growth.