Optimum Nutrition vs Isopure
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These two are closer than the marketing suggests, and they carry the same certification. ON Gold Standard wins on price per gram, flavour range and taste, because the whey concentrate in the blend carries flavour that pure isolate cannot. Isopure Zero Carb wins on the nutrition label: 0g carbs, 0g sugar, trace lactose and 100 calories. Pick on whether carbs and lactose matter to you, not on which brand is “better”.
ON Gold Standard
24g protein, 120 calories per single scoop. Whey isolate-led blend with concentrate and peptides. Informed Choice certified. 20+ flavours. $54.99 for 2lb / 29 servings from optimumnutrition.com May 2026.
Check current price on Amazon →Isopure Zero Carb
25g protein, 100 calories per scoop. 100% microfiltered whey isolate. 0g carbs, 0g sugar, trace lactose. Informed Choice certified. 8 flavours. $87.99 for 3lb / 42 servings from theisopurecompany.com May 2026.
Check current price on Amazon →At a glance
- Both are Informed Choice certified: on third-party testing this is a tie
- Isopure is leaner: 25g protein at 100 calories versus 24g at 120
- Isopure has 0g carbs and trace lactose; Gold Standard has 3g carbs and more lactose
- Gold Standard costs less per gram of protein (about $0.079 vs $0.084 at list price)
- Gold Standard has 20+ flavours against Isopure’s 8, and tastes noticeably richer
Head-to-Head
| ON Gold Standard | Isopure Zero Carb | |
|---|---|---|
| Protein per serving | 24g | 25g |
| Calories per serving | 120 | 100 |
| Carbs / sugar | 3g / 1g | 0g / 0g |
| Fat | 1–1.5g | 0.5g |
| Protein type | Whey isolate, concentrate and peptides | 100% microfiltered whey isolate |
| Lactose | Present (concentrate in blend) | Trace, under 1g |
| Certification | Informed Choice | Informed Choice |
| Flavour count | 20+ | 8 |
| Brand-direct price | $54.99 / 2lb / 29 servings (optimumnutrition.com May 2026) | $87.99 / 3lb / 42 servings (theisopurecompany.com May 2026) |
| Cost per gram of protein | ≈$0.079 | ≈$0.084 |
| Best for | Everyday value, flavour variety | Keto, carb tracking, lactose sensitivity |
ON Gold Standard 100% Whey
The data: 24g protein per 30.4g scoop, 120 calories, 3g carbs, 1 to 1.5g fat, 5.5g naturally occurring BCAAs. Whey protein isolates lead the blend, supported by concentrate and whey peptides. Informed Choice certified. 20+ flavours including Double Rich Chocolate, Vanilla Ice Cream and Unflavored. From optimumnutrition.com, May 2026: 2lb (29 servings) $54.99 regular, $44.00 on sale. The 5lb and 10lb sizes cut the per-serving cost significantly.
Who it’s for: Everyday buyers who want the proven benchmark formula at mid-market pricing, and anyone who cares about flavour. The concentrate in the blend is what makes it taste like a milkshake rather than thin flavoured water. Buyers who want variety, a 30-year formula track record, and the lowest cost per gram of the two.
The honest critique: Sucralose and acesulfame potassium appear in every flavoured variant, with Unflavored the only escape inside the range. The 3g of carbs and the residual lactose from the concentrate make it the wrong choice if you are tracking carbs strictly or are lactose intolerant. At 120 calories for 24g it is slightly less calorie-efficient than Isopure.
Check current ON Gold Standard price on Amazon →Isopure Zero Carb Whey Isolate
The data: 25g protein per scoop, 100 calories, 0g carbs, 0g sugar, 0.5g fat. 100% microfiltered whey protein isolate. Trace lactose, under 1g per serving, which most lactose-intolerant users tolerate. Informed Choice certified. Eight flavours including Dutch Chocolate, Cookies & Cream, Alpine Punch and a genuinely unflavoured Unflavored. From theisopurecompany.com, May 2026: 3lb (42 servings) $87.99 regular, $70.40 on sale.
Who it’s for: Anyone on keto or tracking carbohydrates precisely, where 3g per serving actually matters. People managing lactose intolerance who still want whey rather than a plant protein. Buyers who want the highest protein-to-calorie ratio available in mainstream whey, and cooks who need a genuinely neutral unflavoured powder that will not clash with savoury recipes.
The honest critique: Thinner flavour profile than concentrate-based powders. The microfiltration that strips the carbs and fat also removes flavour compounds, so Isopure consistently tastes thinner than Gold Standard mixed at the same volume. This is inherent to pure isolate rather than a quality defect, but anyone switching from Gold Standard will notice immediately. Mix with milk instead of water if it bothers you. It also costs more per gram of protein.
Check current Isopure Zero Carb price on Amazon →Which Should You Buy?
Choose ON Gold Standard if
- You want the lowest cost per gram of protein
- Taste and flavour variety matter to you (20+ options)
- 3g of carbs per serving is irrelevant to your diet
- You have no lactose sensitivity
Choose Isopure Zero Carb if
- You are on keto or tracking carbs strictly
- You are lactose intolerant but want whey, not plant protein
- You want the leanest option: 25g protein at 100 calories
- You need a genuinely neutral unflavoured powder for cooking
FAQ
Is Isopure better than Optimum Nutrition Gold Standard?
Neither is better outright, and both carry the same Informed Choice certification. Isopure Zero Carb is 100% whey isolate at 25g protein and 100 calories with 0g carbs and trace lactose, which makes it the better pick for keto, carb tracking, or lactose sensitivity. ON Gold Standard is an isolate-led blend at 24g protein and 120 calories, costs less per gram, and has 20+ flavours against Isopure’s 8.
Which is cheaper per gram of protein, ON or Isopure?
ON Gold Standard. At optimumnutrition.com May 2026 pricing the 2lb tub is $54.99 for 29 servings, about $1.90 per serving or roughly $0.079 per gram of protein. At theisopurecompany.com May 2026 pricing the 3lb Isopure tub is $87.99 for 42 servings, about $2.10 per serving or roughly $0.084 per gram. Both run frequent sales, and ON’s larger sizes reduce cost per serving considerably further.
Is Isopure better for lactose intolerance than Gold Standard?
Yes. Isopure Zero Carb is 100% microfiltered whey isolate with trace lactose, under 1g per serving. Gold Standard is an isolate-led blend that also contains whey concentrate, and concentrate retains more lactose. If lactose is the deciding factor, choose Isopure Zero Carb or ON’s separate Gold Standard 100% Whey Isolate product.
Do both brands carry third-party certification?
Yes, and it is a genuine tie. Both are Informed Choice certified, meaning batch-tested for banned substances by an independent body. Neither carries NSF Certified for Sport, the stricter tier some Olympic and professional governing bodies require. See our safety testing guide for what each certification actually verifies.
Related Resources
- Read the full Optimum Nutrition brand review
- Read the full Isopure brand review
- See Isopure vs Transparent Labs for isolate against clean-label
- See Dymatize vs Isopure for the two big isolate brands head to head
- See ON vs Myprotein for the value-tier comparison
- Understand whey isolate vs concentrate before choosing
- See our best protein powder guide for picks across all categories
Last reviewed: by the protein.supply editorial team.