We score every product on the same six criteria used for the ProEnergy review: protein purity, ingredient quality, sweetener profile, transparency, taste and mixability, and value per gram — equally weighted, averaged to one decimal. Full method on the About page. Where a figure couldn’t be verified at a credible source, that criterion is left out of the average rather than estimated, and the review says so.
Transparent Labs 100% Grass-Fed Whey Protein Isolate — 7.6/10 (scored on 5 of 6 criteria)
Transparent Labs’ isolate is the real thing — a single-source isolate, not a blend, sweetened only with stevia and carrying 0g added sugar. It backs that up with the strongest transparency record of any product here: batch-level, lab-signed Certificates of Analysis published and linked directly from the product page, something almost none of its competitors do. It falls short of a 90%+ purity bar at roughly 80–82% protein by scoop weight, and it doesn’t say where the milk itself comes from — “grass-fed” is claimed without naming a country or farm, and no cold-processing method is specified. We couldn’t find a large enough, product-specific body of verified customer feedback on taste and mixability to score that criterion with confidence, so it’s left blank rather than guessed. At $0.071 per gram of protein, it’s mid-to-premium priced.
Sources: transparentlabs.com, Certificate of Analysis, Trustpilot
Jay Robb Grass-Fed Whey Protein Isolate — 7.2/10
Jay Robb is a genuine, cold-processed, cross-flow microfiltered isolate — not a concentrate — sweetened only with stevia, and it earns the best-reviewed taste and mixability of any competitor we checked: buyers on ObesityHelp and Walmart consistently call it the best-tasting protein they’ve found, with minimal aftertaste and no foaming. It falls just short of a 90%+ purity standard (81–87% by weight depending on flavor) purely because of added flavoring and stevia, and while it claims grass-fed, non-rBGH sourcing, it doesn’t name a specific farm or country (“secures large quantities abroad”). We found no published batch-level or third-party lab test results linked from the product page. At $0.075 per gram of protein, it’s mid-priced.
Sources: jayrobb.com, ObesityHelp reviews, H-E-B
Isopure Zero Carb (Unflavored) — 6.6/10
Isopure’s unflavored isolate is about as simple as a label gets: whey protein isolate and a trace of lecithin, nothing else, zero sugar, zero added sweetener. Buyers on iHerb rate it 4.6 out of 5 across more than 2,700 ratings and consistently describe it as nearly tasteless and easy to mix into food or drinks without clumping. Where it comes up short: at 86.2% protein by weight it’s just under the isolate-purity bar, and Isopure discloses no milk sourcing, no filtration method, and no batch-level or third-party lab test results anywhere on its own site — a real transparency gap for a brand at this price. Flavored versions trade the clean label for sucralose. At $0.077 per gram of protein, it’s mid-priced.
Sources: iHerb, theisopurecompany.com, Walmart
Naked Whey (Unflavored) — 6.2/10
Naked Whey is upfront about what it is: a single-ingredient, grass-fed whey protein concentrate, not an isolate, at roughly 82% protein by weight — no gums, no artificial sweeteners in the unflavored version. Where it falls down is transparency: the company’s own FAQ states it will not release lab reports to customers “as we are prohibited from doing so by the lab,” and its “cold-processed” marketing sits oddly next to that same FAQ’s admission that the whey is heated to 163°F during processing — a discrepancy we couldn’t resolve from public sourcing. Amazon buyers rate it 4.2 out of 5 across a very large review base, with a recurring complaint that it doesn’t mix well with liquids. At $0.074 per gram of protein, it’s mid-priced for a concentrate.
Sources: nakednutrition.com, Naked Nutrition FAQ, Garage Gym Reviews
Optimum Nutrition Gold Standard 100% Whey — 5.1/10
Gold Standard is the category’s default bestseller for a reason: it dissolves cleanly even in plain water, and buyers on Amazon rate it 4.6–4.7 out of 5 across more than 130,000 ratings, consistently praising the taste across its large flavor lineup — the strongest taste record in this comparison. But the “100%” in the name refers to 100% whey, not 100% isolate: it’s an undisclosed-ratio blend of isolate, concentrate, and whey peptides at about 79% protein by weight, sweetened with acesulfame potassium rather than a natural sweetener, and milk sourcing is disclosed only as “cow’s milk” with no further detail. Optimum Nutrition doesn’t publish batch-level lab results on the product page. At $0.054 per gram of protein, it’s the best value in this comparison by a wide margin.
Sources: optimumnutrition.com, NIH Dietary Supplement Label Database, Walmart
NOW Foods Whey Protein — 4.4/10
NOW’s flagship whey earns real praise for taste and mixability — iHerb buyers rate it 4.7 out of 5, describing the texture as “silky rather than chalky” — and it carries genuine third-party Informed Sport certification against banned substances. But it’s the least pure product in this comparison: an undisclosed-ratio blend of concentrate and isolate at just 57% protein by weight, sweetened with xylitol (a sugar alcohol) alongside stevia, with no milk-sourcing or filtration claim anywhere on the product page, and no batch-level Certificate of Analysis linked from it. At $0.074 per gram of protein, it isn’t actually the budget option its reputation suggests once you price it per gram of protein rather than per jar.
Sources: nowfoods.com, iHerb, Vitacost
Dymatize ISO100 — 4.3/10
ISO100 has the best-corroborated taste and mixability record we found outside of Jay Robb — reviewers on Bodybuilding.com (9.3/10, 2,387 ratings) and Vitamin Shoppe (4.4/5, 522 ratings) repeatedly call it smooth and clump-free, especially in the chocolate flavors. It’s a genuine isolate (hydrolyzed isolate plus isolate, no concentrate), but at 78% protein by weight it’s diluted well below the 90%+ bar, it’s sweetened with sucralose alongside stevia, its milk sourcing is undisclosed, and — despite a banned-substance testing badge — Dymatize doesn’t publish batch-level lab results on its product pages. At $0.095 per gram of protein, it’s the most expensive product in this comparison.
Sources: dymatize.com, Bodybuilding.com, Vitamin Shoppe