The Protein Glossary

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Every protein-powder term, ingredient, certification and acronym you will ever see on a supplement label, explained in plain English. 54 entries, each linked to real products from our live catalog of 702 tracked tubs and bars.

54
Terms defined
A to W
Alphabetical
702
Products linked

Supplement labels are written for people who already know what they are looking at. The acronyms (WPC, WPI, BCAA, EAA, DIAAS), the certifications (NSF Certified for Sport, Informed Sport, USP Verified, GMP, USDA Organic), the marketing claims ('proprietary blend,' 'native whey,' 'grass-fed,' 'time-released') and the label math (protein per serving, scoop size, servings per container, net carbs) all overlap into a wall of jargon that hides whether the tub in your hand is genuinely worth its price.

This glossary is the cheat sheet. Every term in it gets a short plain-English answer at the top, a 'Why It Matters' explanation of when the term actually changes your decision, a 'How to Spot It on a Label' breakdown for the supermarket aisle, two or three example products from our live catalog, and three to five related entries to keep learning. We update every entry whenever the underlying research or US-market pricing changes meaningfully.

The fastest path through this page: if you are shopping right now, jump to Value Score, Cost Per Gram and Protein Per Serving. If you are trying to decide between whey concentrate and isolate, start with Whey Protein and follow the related links. If you are vegan, begin at Vegan and Pea Protein. If you compete in a tested sport, the only entry that matters first is NSF Certified for Sport.

Browse by Category

Amino Acids and Biology

Whey and Milk Proteins

Plant Proteins

Collagen and Specialty

Protein Quality Metrics

Certifications and Trust

Sourcing and Label Claims

Reading the Label

Sweeteners and Ingredients

Value and Timing

Product Formats

A

Amino Acid Spiking Label Math
Amino acid spiking is when manufacturers add cheap free amino acids (taurine, glycine, glutamine) to a protein powder to inflate the total nitrogen content. Because protein content is measured by nitrogen, spiked products test higher than the actual intact protein they contain.
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Anabolic Window Timing
The anabolic window is the post-exercise period during which muscle protein synthesis is most responsive to dietary protein. The classic claim was a strict 30 to 60 minutes; modern evidence suggests it is more like 3 to 6 hours, and that total daily protein intake matters more than the precise timing of a post-workout shake.
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Artificial Sweeteners Ingredient
Artificial sweeteners are non-caloric or near-zero-calorie compounds used to sweeten protein powders without adding sugar or carbs. The most common in protein supplements are sucralose, acesulfame potassium (Ace-K) and aspartame. Plant-derived alternatives include stevia and monk fruit.
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B

BCAA Acronym
BCAA stands for Branched-Chain Amino Acids: the trio of leucine, isoleucine and valine. They make up about a third of muscle protein and trigger most of the immediate muscle-building signal after a meal. Any quality whey already contains 5 to 6 grams of BCAAs per serve.
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Biological Value Quality
Biological Value (BV) is an older protein-quality measure that ranks how efficiently your body retains absorbed nitrogen from a protein. Whole egg scores 100; whey scores 104 to 159 depending on the form; casein scores about 77; soy scores about 74; collagen scores very low.
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C

Casein Protein Slow-Digesting
Casein is the slow-digesting milk protein that makes up about 80 percent of the protein in cow's milk. It curdles in the stomach and releases amino acids gradually over 6 to 8 hours. Most people drink casein before bed to keep amino acids high overnight.
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Clear Protein Water Category
Clear protein water is a juice-like protein drink made with whey protein isolate (or hydrolysate) that has been processed to dissolve clear rather than milky. The texture is light and refreshing, often citrus-flavored, with 15 to 25 grams of protein per bottle.
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Collagen Peptides Specialty
Collagen peptides are short-chain proteins derived from animal connective tissue (hide, bone, fish skin) that have been broken down for easier digestion. Marketed for skin, hair, joints and nails, collagen lacks tryptophan, which means it is not a complete protein and should not be your main protein source.
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Complete Protein Quality
A complete protein is a source that contains all nine essential amino acids in meaningful quantities. Whey, casein, egg, soy, beef and most other animal proteins are complete. Single-source plant proteins like pea, rice or hemp are usually low in one or two essentials and need to be blended.
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Cost Per Gram of Protein The Metric
Cost per gram of protein is the single most important value metric: how many dollars (or cents) you pay for each gram of actual protein. Calculated as: price divided by (servings per tub times protein per serving). In 2026 the floor for cheap whey is about $0.0174 per gram.
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D

DIAAS Quality
DIAAS stands for Digestible Indispensable Amino Acid Score. It is the modern replacement for PDCAAS, with no 1.0 cap. Whey isolate scores about 1.09, milk protein about 1.18, egg about 1.13, and soy isolate around 0.91. Plant proteins score lower than their PDCAAS counterparts.
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E

EAA Acronym
EAA stands for 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.
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G

Gluten-Free Label Claim
Gluten-free means a product contains fewer than 20 parts per million of gluten, the protein found in wheat, barley and rye. Most whey, casein, soy and pea proteins are naturally gluten-free; the risk is cross-contamination at facilities that also process gluten-containing products.
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GMP Certified Trust
GMP stands for Good Manufacturing Practices. A GMP-certified facility has been audited to confirm consistent quality control, sanitation, and record-keeping. In the US, GMP compliance is technically required by the FDA but the certification provides independent verification.
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Grass-Fed Whey Sourcing
Grass-fed whey is 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, more CLA), but the protein itself is nutritionally very similar to conventional whey.
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H

Hemp Protein Plant
Hemp protein is made by milling and defatting hemp seeds into a powder. It contains all nine essential amino acids but in low ratios, plus useful amounts of fiber, omega-3 fats and minerals. Hemp is usually a fiber-and-nutrition supplement first and a protein supplement second.
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Hydrolyzed Collagen Specialty
Hydrolyzed collagen is collagen protein that has been enzymatically broken down into shorter peptide fragments. Hydrolysis improves solubility (it mixes cold without clumping) and may improve absorption. The terms hydrolyzed collagen and collagen peptides are used interchangeably on most labels.
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I

Informed Sport Trust
Informed Sport is a UK-based third-party testing program that screens every production batch of a certified product against the WADA banned-substance list. It is widely used by European brands and is the de facto standard for British and European tested athletes.
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Isoleucine Amino Acid
Isoleucine is one of the three branched-chain amino acids (alongside leucine and valine) and one of the nine essentials your body cannot make on its own. It supports glucose uptake into muscle cells and contributes to hemoglobin production.
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L

Lactose-Free Label Claim
Lactose-free whey contains less than 1 gram of lactose per serving, low enough that most lactose-intolerant adults can tolerate it. Whey isolate is naturally near-lactose-free; whey concentrate retains 3 to 8g of lactose per scoop and is more likely to cause bloating.
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Leucine Key Nutrient
Leucine is the single most important amino acid for muscle protein synthesis. Hitting around 2.5 to 3 grams of leucine per meal is the well-studied threshold for maximally turning on muscle building, which is why one scoop of quality whey (about 2.5g leucine) is so effective.
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M

Micellar Casein Slow-Digesting
Micellar casein is the form of casein where the original spherical micelle structure of the protein is preserved through gentle filtration. This is the slowest-releasing protein you can buy and the standard pick for before-bed shakes.
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Monk Fruit Ingredient
Monk fruit (luo han guo) is a plant-derived sweetener extracted from the luo han guo melon. Its sweetening compounds, mogrosides, are 150 to 250 times sweeter than sugar. Monk fruit has zero calories and a cleaner aftertaste than stevia, which is why it is rising in popularity.
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mTOR Biology
mTOR (mechanistic target of rapamycin) is the cellular pathway that controls muscle protein synthesis. When you eat enough leucine in a meal (about 2.5 to 3g), mTOR is activated and the cell starts building new muscle protein. Without enough leucine, mTOR stays off.
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Muscle Protein Synthesis Biology
Muscle Protein Synthesis (MPS) is the process by which your body builds new muscle protein from amino acids. MPS happens in response to eating enough protein and to resistance training. The biggest single trigger is leucine reaching the 2.5 to 3g threshold in a meal.
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N

Native Whey Premium
Native whey is whey protein extracted directly from skim milk through cold microfiltration, rather than as a by-product of cheese-making. Native whey undergoes less heat and acid processing, retains more intact protein fractions, and tends to be lower in lactose. It is also significantly more expensive than conventional whey.
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Net Carbs Label Math
Net carbs is total carbohydrates minus fiber and sugar alcohols. The math approximates how many digestible carbs raise blood sugar. Whey isolate typically has 1 to 2g net carbs per serving; mass gainers can have 60 to 100g; protein bars vary from 2 to 25g.
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Non-GMO Label Claim
Non-GMO means a product is made without ingredients from genetically modified organisms. For animal proteins like whey, this usually refers to the feed the source animals ate (no GMO corn or soy). The Non-GMO Project butterfly seal is the most recognized US verification.
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NSF Certified for Sport Trust
NSF Certified for Sport is the gold-standard third-party testing program for athletes. Products are tested for banned substances, heavy metals, microbial contamination, and label accuracy. The certification mark is required by the NFL, MLB, NHL and most college athletic programs.
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O

Organic Label Claim
Organic protein products are certified by the USDA to come from sources grown or raised without synthetic pesticides, synthetic fertilizers, antibiotics, growth hormones, or GMO inputs. Organic certification is the strictest sourcing claim on a protein label.
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P

PDCAAS Quality
PDCAAS stands for Protein Digestibility-Corrected Amino Acid Score. It is the FDA's official method for ranking the quality of a protein, scoring from 0 to 1. Whey, casein, egg and soy all score the maximum 1.0; rice and pea score 0.7 to 0.8; collagen and gelatin score very low.
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Pea Protein Plant
Pea protein is extracted from yellow split peas and is the dominant plant protein on the market. It is high in BCAAs (especially leucine) and arginine, but limited in methionine. That is why it is almost always blended with rice protein to create a complete amino profile.
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Post-Workout Protein Timing
Post-workout protein is a 20 to 40g serving of fast-digesting protein consumed within 30 to 60 minutes after training. It supplies amino acids during the period of heightened muscle protein synthesis sensitivity that follows resistance exercise.
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Pre-Workout Protein Timing
Pre-workout protein is a 20 to 30g serving of fast-digesting protein (typically whey or whey isolate) consumed 30 to 60 minutes before training. It primes muscle protein synthesis during the workout and may slightly reduce post-workout soreness compared to fasted training.
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Proprietary Blend Label Math
A proprietary blend is a label trick that lists multiple ingredients under a single total weight, without disclosing how much of each is included. Proprietary blends let manufacturers hide cheap fillers and underdose expensive ingredients.
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Protein Bar Category
Protein bars are solid-form protein snacks combining whey, casein, milk protein isolate, soy or pea protein with binders, fats, sweeteners and sometimes chocolate coating. A typical bar delivers 15 to 25g of protein in a 50 to 70g serving with 150 to 250 calories.
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Protein Per Serving Label Math
Protein per serving is the most important single number on a protein-powder label: how many grams of actual protein are in one scoop. Quality powders deliver 20 to 30 grams per serving. Mass gainers, meal-replacements and some 'protein cereals' deliver surprisingly little protein per scoop.
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R

Ready-To-Drink (RTD) Category
Ready-to-drink (RTD) protein is a pre-mixed, shelf-stable protein shake sold in a bottle or carton, typically containing 20 to 30 grams of protein per serving. RTDs trade some cost efficiency for convenience: you pay roughly 2 to 3 times more per gram of protein than mixing your own powder.
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Rice Protein Plant
Rice protein is extracted from brown rice and is one of the most hypoallergenic plant proteins on the market. It is high in methionine but low in lysine, which is why it is almost always blended with pea or soy protein to make a complete amino profile.
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S

Scoop Size Label Math
Scoop size is the total weight of one serving of powder, measured in grams. A typical whey scoop is 27 to 35g; an isolate scoop is 27 to 30g; a mass gainer scoop is 100g or more. Smaller, denser scoops generally indicate higher-purity protein.
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Soy Protein Plant
Soy protein is a complete plant protein extracted from soybeans. It contains every essential amino acid, has a long research history, and matches whey in most muscle-building studies. Soy isolate is the most refined form and is used in many ready-to-drink shakes.
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Stevia Ingredient
Stevia is a plant-derived sweetener extracted from the Stevia rebaudiana leaf. The two main sweetening compounds are stevioside and rebaudioside A (Reb A). Stevia is 200 to 400 times sweeter than sugar, has zero calories, and is the default sweetener for natural-positioned proteins.
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Subscribe and Save Value
Subscribe and Save is the Amazon (and increasingly other retailer) discount program where you commit to a recurring delivery of a product in exchange for a 5 to 15 percent discount. For high-volume protein buyers, Subscribe and Save can be the cheapest legitimate way to buy whey.
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Sucralose Ingredient
Sucralose (brand name Splenda) is the most common artificial sweetener in protein powders. It is about 600 times sweeter than sugar, contains no calories, and is stable in heat and acid. The FDA approved it in 1998 and considers it safe at typical doses.
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T

Third-Party Tested Trust
Third-party tested is a general claim that an outside lab (not the manufacturer's own quality control) has verified protein content, ingredient identity, or absence of contaminants. Common testing partners include Informed Sport, NSF, Labdoor and ConsumerLab.
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U

USP Verified Trust
USP Verified is a US Pharmacopeia certification program that verifies that a supplement contains the ingredients listed on the label, in the declared potencies, and is free of harmful contaminants. The USP seal is one of the strictest non-pharmaceutical quality marks available.
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V

Valine Amino Acid
Valine is the third branched-chain amino acid (after leucine and isoleucine) and one of the nine essentials. It supports energy production during long training sessions and helps repair muscle tissue post-exercise.
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Value Score The Metric
Value Score is ProteinPrice.com's 0 to 100 ranking of how much protein you get per dollar at the current lowest price across our 12 tracked retailers. A score above 90 is excellent value. Value Score updates automatically whenever a tracked price changes.
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Vegan Label Claim
Vegan protein products contain no animal-derived ingredients. The protein base is typically pea, rice, soy, hemp, pumpkin or oat. Look for vegan-certified seals (Certified Vegan, Vegan Action) for the most reliable verification.
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W

Whey Concentrate Whey Format
Whey protein concentrate (WPC) is the standard 70 to 80 percent protein form of whey. It contains more lactose, fat and bioactive milk fractions than isolate, which makes it richer-tasting and significantly cheaper. WPC is the value sweet spot for most lifters.
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Whey Hydrolysate Whey Format
Whey hydrolysate (sometimes labeled hydrolyzed whey or WPH) is whey protein that has been pre-digested by enzymes into shorter peptide chains. It absorbs even faster than isolate, costs significantly more, and tastes more bitter. For most lifters it is overkill.
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Whey Isolate Whey Format
Whey protein isolate (WPI) is whey that has been filtered further than concentrate, reaching 90 percent or more protein content by weight. Very little lactose, fat or carb remains. WPI is the premium whey format: low calorie, fast digesting and easier on sensitive stomachs.
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Whey Protein Basics
Whey protein is the liquid fraction of milk that separates during cheese-making. Once filtered and spray-dried into a powder, whey is the most studied and most popular protein supplement on earth. It digests in roughly 90 minutes and is high in leucine, BCAAs and essential amino acids.
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X

Xanthan Gum Ingredient
Xanthan gum is a polysaccharide thickener and emulsifier produced by fermenting sugar with the bacterium Xanthomonas campestris. In protein powders, it is added at very small doses (under 1 percent) to improve mouthfeel, prevent separation, and keep flavors evenly distributed.
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