Head to head · Protein Powder
Optimum Nutrition Gold Standard 100% Casein vs Transparent Labs 100% Grass-Fed Whey Protein Isolate
Transparent Labs scores higher overall (8.8 vs 8.1 out of 10), mainly on efficacy, quality & purity and transparency. Optimum Nutrition still leads on value.
Updated September 2026 from our full reviews · How we score
A slow-digesting micellar casein with 24 g of protein per scoop for bedtime or long gaps between meals; thick, filling and fairly priced.
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A grass-fed whey isolate with 28 g of protein per scoop, stevia instead of artificial sweeteners, and NSF Certified for Sport status.
We may earn a commission when you buy through these links — it never affects our scores. How we make money
We may earn a commission when you buy through these links — it never affects our scores. How we make money
The short answer
Choose Optimum Nutrition if…
- A slow-digesting shake before bed
- Staying full between meals
- Thick shakes and protein puddings
- You care most about value
Choose Transparent Labs if…
- Drug-tested athletes
- Clean-label shoppers avoiding artificial sweeteners
- People who want grass-fed sourcing
- Lactose-sensitive lifters
- You care most about efficacy, quality & purity, transparency
Side by side
| Gold Standard 100% Casein | 100% Grass-Fed Whey Protein Isolate | |
|---|---|---|
| Our score | 8.1 / 10 | 8.8 / 10 |
| Efficacy (30%) | 8.3 | 9.1 |
| Quality & Purity (25%) | 7.4 | 9.4 |
| Value (20%) | 8.6 | 7.4 |
| Experience (15%) | 8.5 | 8.6 |
| Transparency (10%) | 7.8 | 9.5 |
| Form | Powder | Powder |
| Serving | 1 scoop (34 g)53 servings per container | 1 scoop (34.9 g)30 servings per container |
| Price per serving | See retailer | $2.17 |
| Testing & certifications | None verified | NSF Certified for SportInformed Choice |
| Dietary | Gluten-free | Gluten-free |
| Key ingredients |
|
|
| Flavors | 4 (Chocolate Supreme, Creamy Vanilla, Chocolate Peanut Butter…) | 8 (Milk Chocolate, French Vanilla, Dark Chocolate…) |
| Creator video reviews | 3 | 5 |
Pros and cons
Gold Standard 100% Casein
- 24 g of micellar casein protein per 120-calorie scoop
- Adds 500 mg of calcium and 100% of the Daily Value for zinc
- About $1.40 per serving, good value for casein
- 4.6 stars from more than 9,000 buyer ratings, with many saying it keeps them full
- Not listed among ON's Informed Choice-certified products
- Sweetened with both acesulfame potassium and sucralose, plus artificial flavor
- Thick texture and mixability get mixed reviews
- One scoop is below the 30 to 40 g used in most pre-sleep protein studies
100% Grass-Fed Whey Protein Isolate
- 28 g of protein per scoop from grass-fed whey isolate
- Listed in NSF's Certified for Sport database and certified by Informed Choice (per the brand)
- Every ingredient disclosed by weight, with batch test results published online
- No artificial sweeteners, dyes or preservatives
- buyers frequently describe it as easy on the stomach
- About $2.17 per serving for the 30-serving tub, well above whey blends
- Stevia can leave an aftertaste some people dislike
- Made on equipment that also processes eggs, soy, wheat, shellfish, fish oil, tree nuts and peanut oil, and some flavors contain peanuts
- Mostly sold through the brand site and Amazon, so in-store discounts are rare
Our verdicts
Gold Standard 100% Casein
Gold Standard 100% Casein is a dependable, well-priced micellar casein for nighttime or between-meal protein, with good flavor and a filling texture. It lacks the named third-party certification of ON's whey and uses artificial sweeteners, but for most people who want a slow-digesting shake it does the job at a fair price.
Full review
100% Grass-Fed Whey Protein Isolate
For shoppers who prioritize ingredient transparency and third-party verification, this is one of the strongest whey isolates available: 28 g of protein, a short stevia-sweetened ingredient list, NSF Certified for Sport status and public batch testing. The trade-off is price, at more than $2 per serving, and stevia's flavor will not suit everyone.
Full review
What creators say
Questions people ask
Is Optimum Nutrition better than Transparent Labs?
Are Optimum Nutrition and Transparent Labs third-party tested?
Who should choose Optimum Nutrition over Transparent Labs?
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