SAC StudioThe premium grass-fed minimalist — cold-processed, additive-free casein, but no third-party seal.
ProMix Casein is the premium grass-fed pick for purists who want sourcing and a clean label together. It's a cold-processed, acid-free micellar casein from pasture-raised cows, with no artificial sweeteners, gums or fillers, delivering 25 g of protein per serving (BCAA content isn't broken out on the label). It overlaps with Naked on the additive-free, unflavored philosophy but leans harder into the grass-fed, cold-processed story, and it's soy-free, non-GMO and made without added hormones.
The catches are a premium price per serving, the unflavored-only format, and the lack of a formal banned-substance certification — the brand's clean-sourcing claims are disclosed but not third-party certified on the listing. If you specifically want grass-fed, minimally-processed casein and don't mind flavoring it yourself, it earns its spot, just a notch behind the certified minimalist above it.
It's cold-processed, acid-free micellar casein — the acid-free processing is a genuine plus, since it avoids the harsher methods that produce faster-digesting caseinate — from grass-fed dairy, unflavored with just sunflower lecithin for mixing. That's a clean, minimally-processed form. It scores solidly rather than at the very top here because a few picks edge it on pure form specificity, but the additive-free, cold-processed micellar profile is exactly what this axis wants.
A strong axis: 25 g of protein per serving with low carbs and no added sugar — a lean, night-appropriate macro from a clean, additive-free base. It scores among the better protein/macro results in the lineup, reflecting a full 25 g dose with nothing diluting it. Two caveats: that 25 g comes from a 2-scoop serving, and the Supplement Facts panel doesn't break out a BCAA figure — an earlier version of this review cited 5.3 g of BCAAs, which isn't stated on the label, so we're not crediting a number we can't verify.
The honest read: ProMix makes disclosed clean-sourcing claims — soy-free, non-GMO, no added hormones, grass-fed — but carries no Informed Sport or NSF banned-substance seal. Those are manufacturer claims, not an independent certification, and we won't frame them as one. It scores below the certified picks on this axis for exactly that reason; if you need a verified seal, Naked (NSF) or the Informed Sport pair are the choices.
At about $50 for a 2.5 lb bag of ~39 servings, cost per serving lands near $1.30 — premium, driven by the grass-fed sourcing and cold processing. It's fair value for what it is, but on pure price per gram of protein it can't match Dymatize or the unflavored bulk bags. A reasonable but not standout value, consistent with a premium-sourcing product.
The weak axis, as with all the unflavored picks: there's no flavor to rate and plain casein is bland and thick. The sunflower lecithin helps it mix better than raw casein, and it blends fine into oats, yogurt or a flavored smoothie, but on its own it's not something you'll enjoy drinking. Lowest weight, and the expected trade-off of an additive-free, unflavored powder.
“Grass-fed, pasture-raised, cold-processed acid-free micellar casein.”
These are disclosed sourcing and processing claims from the brand. Acid-free cold processing is genuinely relevant — it helps preserve the intact micellar structure rather than producing faster-digesting caseinate — but the grass-fed/pasture-raised sourcing isn't independently certified on the listing, so it's a credible manufacturer claim, not a verified seal.
“Additive-free — no artificial sweeteners, gums or fillers.”
The label is an unflavored single ingredient plus sunflower lecithin as a mixing aid, with no sweeteners, gums or fillers — a genuinely minimal, verifiable formula.
“25 g of protein per serving.”
The nutrition panel states 25 g protein per serving — accurate, with the honest note that it's a 2-scoop serving. The panel does not break out a BCAA figure, so we no longer cite a BCAA number for this product.
“Soy-free, non-GMO, no added hormones.”
Soy-free is consistent with the sunflower-lecithin formula. Non-GMO and no-added-hormones are disclosed supply claims from the brand; without an Informed Sport/NSF seal or a published third-party audit on the listing, they're credible manufacturer statements rather than independently certified facts.
“Premium quality casein for muscle building.”
It's a genuinely clean, well-sourced casein, so 'premium quality' is fair. But 'for muscle building' rests on general casein/protein evidence (Res 2012 pre-sleep MPS); grass-fed, cold-processed sourcing doesn't add hypertrophy over a well-made casein — total daily protein does that (Morton 2018).
An earlier version of this review said the label lists 5.3 g of BCAAs per serving. The Supplement Facts panel on this listing shows Calories, Total Fat, Cholesterol, Sodium, Total Carbohydrates and Protein (25 g) per 2-scoop serving — no separate BCAA line. We re-read the label on Sep 7, 2026 and corrected every mention of the 5.3 g BCAA figure to reflect that it is not stated on the label.
ProMix fills a precise gap: you want grass-fed, pasture-raised dairy AND a fully additive-free label. It's cold-processed and acid-free (which helps keep the micellar structure intact), 25 g protein, no sweeteners or fillers, soy-free. If that combination is your priority, it's the strongest option for it in the lineup — Naked is the certified minimalist, ProMix is the grass-fed one.
Unlike the marketing fluff on many tubs, the cold-processed, acid-free method matters here: acid or heat processing is what turns casein into faster-digesting caseinate, which defeats the slow-release purpose. Keeping it acid-free helps preserve the intact micellar form. It's one of the few processing claims on this page that connects to an actual functional property.
ProMix leans on disclosed clean-sourcing claims — grass-fed, non-GMO, no added hormones — but carries no Informed Sport or NSF seal. Those are manufacturer statements, not independent certification. That's precisely why it sits a notch behind Naked (#6), which offers a similar additive-free profile plus an actual NSF seal. If verification matters more than grass-fed sourcing, Naked is the better call.
At about $1.30 a serving it's a premium buy, and it's unflavored, so it's bland and thick on its own. Consistent with quality-over-price, it earns its spot on sourcing and clean processing, not on cost. Blend it into oats or a flavored smoothie; don't expect to enjoy it plain. If you want grass-fed but flavored, Legion (#5) is the ready-to-drink alternative.
ProMix Casein is the premium grass-fed pick for purists who want sourcing and a clean label together. It's a cold-processed, acid-free micellar casein from pasture-raised cows, with no artificial sweeteners, gums or fillers, delivering 25 g of protein per serving (BCAA content isn't broken out on the label). It overlaps with Naked on the additive-free philosophy but leans harder into the grass-fed, cold-processed story, and it's soy-free, non-GMO and made without added hormones. The catches are a premium price per serving, the unflavored-only format, and the lack of a formal banned-substance certification — the clean-sourcing claims are disclosed but not third-party certified. If verification matters more, Naked (#6) offers a similar profile plus a real NSF seal; if you want grass-fed but flavored, Legion (#5) is the pick. But if you specifically want grass-fed, minimally-processed casein and don't mind flavoring it yourself, this earns its spot, just behind the certified minimalist above it. (Dairy protein — low lactose, not lactose-free.)
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The certified minimalist sibling: also single-ingredient and additive-free at 26 g, but NSF Certified — trading ProMix's grass-fed sourcing for an actual third-party seal. The pick if verification matters more than pasture-raised dairy.
See it on the list →The flavored grass-fed alternative: also grass-fed and naturally sweetened at 26 g, but ready to drink as a chocolate — the pick if you want the grass-fed story without going unflavored.
See it on the list →The best overall: 100% micellar at 25 g, smooth-mixing chocolate and far better value — but conventional dairy and sucralose-sweetened. The pick if pure form, taste and value beat the grass-fed, additive-free story for you.
See it on the list →Casein before sleep raised overnight muscle protein synthesis versus placebo — supporting a 25 g cold-processed micellar serving like ProMix's for the overnight window.
Casein produced a slow, prolonged amino-acid release and stronger suppression of protein breakdown than whey — the mechanistic reason acid-free cold processing (which preserves the intact micellar form) matters for a true slow release.
Training gains tracked total protein (~1.6 g/kg/day) with no clear source advantage — confirming grass-fed sourcing is a values/quality choice, not a muscle-growth upgrade.
