Head to head · Protein Powder
Isopure Zero Carb Whey Protein Isolate vs Optimum Nutrition Gold Standard 100% Whey
Optimum Nutrition scores higher overall (8.7 vs 7.8 out of 10), mainly on quality & purity, value and experience.
Updated September 2026 from our full reviews · How we score
A true zero-carb whey isolate: 25 g of protein plus a broad vitamin and mineral blend in a 110-calorie scoop, at a price above most rivals.
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The benchmark whey blend: 24 g of protein per 120-calorie scoop, Informed Choice certified, and a flavor lineup few rivals can match.
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 Isopure if…
- Keto and strict low-carb diets
- People who want added vitamins and minerals
- Those who prefer a less-sweet vanilla
Choose Optimum Nutrition if…
- First-time protein powder buyers
- Everyday post-workout shakes
- Drug-tested athletes who want a certified product
- People who like lots of flavor choice
- You care most about quality & purity, value, experience
Side by side
| Zero Carb Whey Protein Isolate | Gold Standard 100% Whey | |
|---|---|---|
| Our score | 7.8 / 10 | 8.7 / 10 |
| Efficacy (30%) | 8.9 | 8.8 |
| Quality & Purity (25%) | 7.4 | 9.0 |
| Value (20%) | 6.8 | 8.3 |
| Experience (15%) | 7.8 | 9.0 |
| Transparency (10%) | 7.8 | 8.0 |
| Form | Powder | Powder |
| Serving | 1 scoop (31 g)40 servings per container | 1 scoop (31 g)74 servings per container |
| Testing & certifications | cGMP facility | Informed Choice |
| Dietary | Gluten-free, Sugar-free, Keto-friendly | Gluten-free |
| Key ingredients |
|
|
| Flavors | 6 (Creamy Vanilla, Cookies & Cream, Strawberries & Cream…) | 8 (Double Rich Chocolate, Extreme Milk Chocolate, Vanilla Ice Cream…) |
| Creator video reviews | 4 | 5 |
Pros and cons
Zero Carb Whey Protein Isolate
- 25 g of protein with 0 g carbs and 0 g sugar per 110-calorie scoop
- All of the protein comes from whey protein isolate
- Broad vitamin and mineral blend, including 100% of the Daily Value for vitamin B12
- Large review base on Amazon (4.6 stars from more than 13,000 ratings)
- No third-party banned-substance certification found; testing is done in-house
- About $2.24 per serving for the 40-serving tub, and more on the brand site
- Contains soy lecithin, sucralose, artificial flavor and xanthan gum
- Flavor and texture draw mixed feedback, with some reviewers calling it gritty or bland
Gold Standard 100% Whey
- 24 g of protein in a 120-calorie, 31 g scoop (about 77% protein by weight)
- Informed Choice certified and regularly tested for banned substances
- More than 20 flavors on the brand's US store, with consistently strong feedback on taste and mixability
- Fully disclosed ingredient list with no proprietary blend
- Widely available on Amazon, TikTok Shop and at major retailers
- Sweetened with acesulfame potassium and uses artificial flavors
- Contains whey concentrate, and a share of buyers report digestive discomfort
- No longer cheap: about $1.39 per serving at typical retail prices for the 5 lb tub, and the brand-site list price is higher
- Servings per tub vary by flavor (roughly 68 to 75 in 5 lb-class tubs), which complicates price comparisons
Our verdicts
Zero Carb Whey Protein Isolate
Isopure Zero Carb does exactly what the name promises: 25 g of isolate protein with no carbs or sugar, plus a vitamin and mineral boost. It is a sensible pick for strict low-carb and keto eaters, but the lack of third-party certification, the artificial sweetener and a price well above rivals such as ISO100 keep it out of the top tier.
Full review
Gold Standard 100% Whey
Gold Standard 100% Whey remains a default recommendation for good reason: a lean 24 g protein dose, banned-substance certification, and taste and mixability endorsed across about 100,000 buyer ratings. It is no longer a bargain, and the concentrate and artificial sweetener will not suit everyone, but few powders balance quality, variety and availability this well.
Full review
What creators say
Questions people ask
Is Isopure better than Optimum Nutrition?
Are Isopure and Optimum Nutrition third-party tested?
Who should choose Isopure over Optimum Nutrition?
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