Protein Glossary

The building blocks of protein. There are 20 amino acids total, and your body needs all of them to build and repair tissue — but 9 of them, called essential amino acids, must come from food.

Branched-chain amino acids — leucine, isoleucine, and valine. Three essential amino acids that play a direct role in muscle recovery and reducing exercise-related fatigue.

Essential amino acids — the 9 amino acids your body cannot produce on its own. They must come from food or supplements, and all 9 are needed for muscle building and repair.

The most important amino acid for triggering muscle protein synthesis. Research shows a threshold of about 2.5 grams per meal is needed to maximize the muscle-building signal.

A dairy protein that digests slowly, providing a sustained release of amino acids over several hours. Often recommended before bed to support overnight muscle repair.

A structural protein that supports skin, joints, hair, and connective tissue. Important: collagen is NOT a complete protein — it scores 0.0 on the PDCAAS scale and cannot replace whey or other complete proteins for muscle building.

A dairy-based protein derived from cheese production. Fast-absorbing, high in leucine, and rated 1.0 on the PDCAAS scale — widely considered the gold standard for muscle preservation.

How efficiently your body absorbs and uses protein from a given source. Higher bioavailability means more of what you eat actually reaches your muscles and tissues.

A protein source that contains all 9 essential amino acids in adequate amounts for human needs. Most animal-based proteins are complete; many plant proteins are not.

Short for macronutrients — protein, carbohydrates, and fat. These are the three main nutrients your body needs in large amounts for energy and tissue building.

The process by which your body builds new muscle tissue. It requires both adequate protein intake and a stimulus like resistance training to work effectively.

Protein Digestibility Corrected Amino Acid Score — a standardized rating of protein quality on a scale of 0 to 1.0, measuring both amino acid completeness and digestibility.

The practice of distributing protein intake across meals throughout the day rather than consuming most of it in one sitting. Spreading protein out produces a stronger muscle-building response.

The feeling of fullness and satisfaction after eating. Protein is the most satiating macronutrient — it keeps you feeling full longer than carbohydrates or fat.

A protein powder containing 70-80% protein by weight, retaining more fat, lactose, and natural compounds than isolate. Less processed and typically more affordable.

Protein that has been pre-digested by breaking it into smaller peptides. Absorbs faster than isolate or concentrate and is the gentlest option for sensitive stomachs.

A protein powder processed to contain 90% or more protein by weight, with most fat, lactose, and carbohydrates removed. The purest common form of protein powder.

The recommended amount of protein powder per use, usually one scoop. Serving sizes vary widely between brands — always check grams of protein per serving, not just scoops.