The Protein Glossary

The building blocks of protein. Twenty different amino acids combine in chains to form every protein in your body, from muscle tissue to enzymes. Nine of them are "essential": meaning you have to get them from food.

Branched-Chain Amino Acids: the trio of leucine, isoleucine and valine. They make up about a third of muscle protein and are the amino acids most directly involved in triggering muscle protein synthesis. Any quality whey already contains 5–6g of BCAAs per serve, so a separate supplement is rarely needed.

How efficiently your body can actually absorb and use a protein. Whey isolate has very high bioavailability and a near-perfect amino acid score; collagen, while popular, has much lower bioavailability for muscle-building purposes because it's missing tryptophan.

How many calories you get per gram of powder. Mass gainers are extremely calorie-dense (often 4–6 calories per gram); isolates are very calorie-sparse (around 4 calories per gram, almost all of it from protein itself).

A slow-digesting milk protein. Casein forms a gel in your stomach and releases amino acids over 6–8 hours, which is why it's often taken before bed. Compared to whey, it's smoother in texture but less ideal for the immediate post-workout window.

Short-chain proteins derived from animal connective tissue (hide, bone, fish skin). Heavily marketed for skin, hair, joints and nails: but because collagen lacks tryptophan, it's not a complete protein and shouldn't be your only protein source.

A protein source that contains all nine essential amino acids in meaningful quantities. Whey, casein, egg, soy and most animal proteins are complete. Single-source plant proteins like pea or rice are usually low in one or two essentials, which is why blends exist.

Whey Protein Concentrate: typically 70–80% protein by weight. Cheaper and richer-tasting than isolate, but it carries more lactose, fat and carbs along with the protein. Usually the best value for cost per gram of protein. See all concentrates →

A cold-temperature filtration method that separates whey protein without using harsh chemicals or heat. It preserves the native protein structure and most bioactive fractions like lactoferrin: and it's the gold-standard process for premium isolates.

Protein whose three-dimensional structure has been altered by heat, acid or processing. Denatured protein is still nutritionally valuable: you denature protein every time you cook an egg: but it loses some bioactive properties that intact native proteins retain.

Essential Amino Acids: the nine amino acids your body cannot manufacture on its own and must obtain from food or supplements. EAA powders contain all nine, whereas BCAA powders contain only three of them.

The most abundant amino acid in your body, important for gut health and immune function. Often added to recovery supplements, but any quality whey already contains a meaningful amount: so a separate glutamine supplement is rarely necessary for healthy adults.

Whey sourced from cows raised primarily on pasture grass rather than grain. The fatty-acid profile of the residual milk fat is slightly different (more omega-3s), but the protein itself is essentially identical to conventional whey.

Protein that has been pre-digested by enzymes into shorter peptide chains. Absorbs faster than intact protein, which is why it's used in clinical and infant nutrition: but it tastes more bitter, costs significantly more and offers minimal benefit for most healthy lifters.

An older isolate process using electrical charge to separate whey protein from other dairy components. It produces extremely high protein content (often 95%+) but can damage some bioactive compounds, which is why most premium brands now prefer microfiltration.

Whey Protein Isolate: typically 90% or more protein by weight, with very little lactose, fat or carbohydrate. The premium whey format, ideal for cutting phases or anyone with mild lactose intolerance. Usually costs 30–50% more than concentrate. See all isolates →

The natural sugar found in milk. Concentrate contains noticeable lactose (3–8g per serving); isolate has only trace amounts (under 1g); and plant proteins contain none. If dairy bothers your stomach, an isolate or a plant blend will usually solve the problem.

The single most important amino acid for triggering muscle protein synthesis. Research suggests around 2.5–3g of leucine per meal is the threshold for maximally stimulating muscle building: which is why one quality scoop of whey (around 2.5g leucine) is so effective.

Medium-Chain Triglycerides: a type of saturated fat that's absorbed quickly and used for energy rather than stored. Sometimes added to keto-friendly protein blends and mass gainers to bump up calories without spiking carbs.

A high-calorie powder combining protein with large amounts of carbs and fat: typically 600–1,300 calories per serving. Designed for hard-gainers struggling to eat enough food to grow. Check the protein-per-calorie ratio carefully: many are mostly maltodextrin.

A physical filtration process that separates whey protein from lactose and fat using extremely fine ceramic or polymer membranes. Gentle on the protein, requires no chemicals, and preserves more of whey's natural bioactive fractions.

Whey extracted directly from skim milk rather than from cheese-making by-product. Native whey undergoes less processing, retains more intact protein fractions, and tends to be lower in lactose: but it's also significantly more expensive than conventional whey.

Made without ingredients from genetically modified organisms. For animal proteins, this usually refers to the feed the source animals ate. The Non-GMO Project's butterfly seal is the most recognised third-party verification in the US.

Plant protein extracted from yellow split peas. High in BCAAs (especially leucine) and arginine, but limited in methionine: which is why it's almost always blended with rice protein to create a complete amino acid profile.

A mix of two or more plant sources: most often pea + rice, sometimes adding hemp, pumpkin, sunflower or chia: designed to deliver a complete amino acid profile that no single plant source can match on its own.

Protein grams divided by serving size, expressed as a percent. A 24g protein scoop weighing 30g is 80% protein: a typical concentrate. A 25g protein scoop weighing 27g is 93% protein: an isolate. Higher percentages mean less filler.

How many grams of actual protein are in one scoop. Quality powders deliver 20–30g per serving. Watch out for mass gainers and meal-replacements that have surprisingly little protein per scoop despite huge calorie counts.

Plant protein extracted from brown rice. Hypoallergenic, easy on digestion, and rich in methionine: but low in lysine. Typically paired with pea protein, since each one fills in the other's amino acid gap.

How many scoops you'll get from one tub. Always check this number: a $35 tub with 30 servings is more expensive per serve than a $40 tub with 50. Total-protein-per-dollar (the metric we rank by) builds servings into the calculation automatically.

A complete plant protein with a longer research history than most. Often avoided due to phytoestrogen concerns, but clinical evidence at typical supplement doses (20–40g per day) is reassuring for both men and women.

The three most common sweeteners in protein powder. Sucralose is artificial and tastes closest to sugar; stevia is plant-derived and has a slight aftertaste; erythritol is a sugar alcohol with near-zero calories and a cooling mouthfeel.

Independently verified by an outside lab: like Informed Sport, NSF Certified for Sport, or Labdoor: for protein content accuracy and the absence of banned substances. Essential for competing athletes and worth looking for as a general quality signal.

A formula combining fast-digesting (whey) and slow-digesting (casein, sometimes egg) proteins to deliver both an immediate amino acid spike and a sustained release over several hours. Useful around training and before long gaps without food.

Servings per tub multiplied by protein per serving. This is the single number that matters for value: total protein grams ÷ price = how much protein you actually get for your money. Every ranking on this site is built on it.

Whey processed without high heat, retaining native protein fractions like lactoferrin, lactoperoxidase and immunoglobulins. Marketed for immune support and gut health. Cold-processed and microfiltered isolates are usually undenatured.

ProteinPrice.com's proprietary 0–100 ranking based purely on grams of protein per dollar at the current lowest price across 12 retailers. The top product gets 100; every other product is scored relative to it. How the score works →

The watery liquid that separates from milk during cheese-making. Once dried into powder, it's the most popular and most thoroughly researched protein supplement in the world: fast-digesting, complete, and rich in leucine.

See Concentrate (WPC). Typically 70–80% protein by weight: the budget-friendly whey format that almost always wins on protein-per-dollar. Browse concentrates →

See Isolate (WPI). 90%+ protein, very low lactose and fat: the premium choice for cutting phases or sensitive stomachs. Browse isolates →