The Best Grass-Fed Whey Protein Isolate
The best grass-fed whey protein isolate is Transparent Labs Grass-Fed Whey Protein Isolate, at $1.93 per 25 g of protein. It is on NSF Certified for Sport and Informed Choice, so outside labs check what is in the tub. It has 28 g of protein a scoop and is sweetened only with stevia.
By Erin Rose Updated October 28, 2026 How we score
Our pick for: Most people
- Protein
- 28 g a scoopIn a 34.3 g scoop
- Per 25 g of protein
- $1.93Less than Legion Whey+, the other isolate here
- A tub
- $64.99French Vanilla, 30 servings, on Amazon
- Testing lists
- NSF Certified for Sport and Informed ChoiceNSF lists the French Vanilla tub
- Calories
- 130 a scoop1 g of carbs, 1 g of sugar
- Sweetened with
- SteviaNo sucralose or sugar alcohols
Why we pick it Transparent Labs says all its whey comes from grass-fed American dairy cows with regular access to pasture. It is the only grass-fed isolate here on a list that also screens for drugs banned in sport, and it has the most protein a scoop here. NSF Certified for Sport lists the French Vanilla tub Amazon sells (listing 1809884). Informed Choice lists the product line too.
What you give up No outside standard backs its grass-fed claim. If you want one that does, or a lower price, see the other picks below.
The best grass-fed whey for your needs
Transparent Labs suits most people. If one of these matters more to you, buy the one made for it. Each one is on a testing list.
Want a certified grass-fed claim: Legion Whey+
Legion says its milk comes from Ireland and is certified to Truly Grass Fed, a named standard for how the cows are fed. It is on NSF/ANSI 173, which checks that the tub holds what the label says and screens for contaminants. That list does not screen for drugs banned in sport. It costs about 17% more than Transparent Labs per 25 g.
Legion Whey+
$2.25 per 25 g · $59.50 a tub (French Vanilla, 30 servings) · 22 g of protein a scoop
Lower price, one ingredient: Naked Whey
Naked Whey is unflavored grass-fed whey and nothing else. It costs about 5% less than Transparent Labs per 25 g. It is a concentrate, so it has more lactose than an isolate. It is on Informed Choice.
Naked Whey
$1.84 per 25 g · $139.99 a tub (Unflavored, 5 lb) · 25 g of protein a scoop
What "grass-fed" means on a whey tub
There is no U.S. government rule for "grass-fed" on a whey label. The USDA withdrew its grass-fed standard, which was written for meat, in 2016. So the claim means what each brand says it means. A few programs set a written standard, such as Truly Grass Fed. Of the 3 labels we read, 1 names one: Legion's.
How to choose a grass-fed whey isolate
Buy one on a testing list for the tub you get
A grass-fed claim tells you about the cows, not about what is in the tub. A testing list checks the tub. NSF Certified for Sport and Informed Choice also screen for drugs banned in sport; NSF/ANSI 173 checks the contents against the label. See which protein powders are third-party tested.
Pick isolate if lactose bothers you
Isolate is filtered further than concentrate. It is typically 0.5 to 1% lactose, against 4 to 8% for an 80% protein concentrate like Naked Whey (U.S. Dairy Export Council spec sheets). It is still milk, so it is not safe with a milk allergy.
Compare the cost of 25 g of protein, not the tub
Scoops differ in size and protein, so a cheap tub can cost more per gram. The table below does the math.
3 grass-fed whey powders compared
Cheapest per 25 g of protein first, at Amazon prices checked November 2, 2026. Some prices include an Amazon deal that day, so the order can change.
| Powder | Cost per 25 g of protein | Why it is or is not the pick |
|---|---|---|
| Naked WheyConcentrate · 25 g of protein a scoop · Informed Choice | $1.84 | A concentrate, not an isolate; lowest price |
| Transparent LabsIsolate · 28 g of protein a scoop · NSF Certified for Sport and Informed Choice | $1.93 | Our pick: two testing lists, including a banned-drug screen |
| Legion Whey+Isolate · 22 g of protein a scoop · NSF/ANSI 173 | $2.25 | The only grass-fed claim tied to a named standard |
The proof for our pick
Here is the NSF listing behind the pick, as we saw it.
The NSF listing
Questions people ask
Is grass-fed whey better than regular whey?
The protein is about the same. In one large U.S. study, milk from cows fed almost only grass had about 2.5 times the omega-3 fat of regular milk. Making an isolate removes most of the fat (Transparent Labs has 0.5 g a scoop), so that extra omega-3 mostly stays behind. The main reason to buy grass-fed whey is how the cows are raised.
How we picked
We looked for grass-fed whey isolates sold on Amazon and searched four testing lists for the exact tub each one sells. We ranked on three things, in this order: a testing list for the tub you buy, the cost of 25 g of protein, and what else is in the scoop. We left out isolates whose testing listing did not match the tub Amazon sells. Not set on grass-fed? See the best whey isolate, the best protein powder of any type, or the protein guide.
Sources
- Amazon listings, Nutrition Facts images and grass-fed claims for Transparent Labs, Legion Whey+ and Naked Whey, read October 28, 2026.
- NSF Certified for Sport listing for Transparent Labs, first read October 5, 2026 and found again in NSF's brand search October 28, 2026: Grass-Fed Whey Protein Isolate French Vanilla 1809884.
- Other testing lists: NSF/ANSI 173 (Legion Whey+ Grass-Fed Whey Isolate French Vanilla); Informed Choice (Transparent Labs, Naked Whey).
- USDA Agricultural Marketing Service, Withdrawal of United States Standards for Livestock and Meat Marketing Claims, Federal Register 81(7):1386, January 12, 2016.
- Benbrook CM, et al. Enhancing the fatty acid profile of milk through forage-based rations, with nutrition modeling of diet outcomes. Food Sci Nutr. 2018. Total omega-3: 0.049 g per 100 g in milk from grass-fed cows, against 0.020 g in conventional milk.
- U.S. Dairy Export Council spec sheets: Whey Protein Isolate and Whey Protein Concentrate 80% (typical lactose).