Protein · Research-based buying guide
Optimum Nutrition Gold Standard 100% Casein Protein Powder: Is it right for you?
A Slow-Digesting Micellar Casein Built for Overnight Recovery
Gold Standard 100% Casein uses micellar casein as its sole protein source. Unlike whey, micellar casein forms a gel in the stomach that releases amino acids gradually, making it a practical choice before sleep or during long stretches without food. Each ~34g scoop delivers 24g protein, 120 calories, 1g fat, 1-2g sugar, 9g naturally occurring EAAs, plus 500mg calcium, 85mg magnesium (20% DV), and 11mg zinc (100% DV). Available in four flavors and two sizes (25- or 53-serving). The manufacturer calls it "banned substance tested" but does not list it under Informed Choice or NSF Certified for Sport. Contains milk and soy. Sweetened with acesulfame potassium and sucralose.
The short answer
Micellar casein with 24g protein, low carbs and fat, plus calcium, magnesium, and zinc. Good before bed or long meal gaps. No named third-party cert; contains milk, soy, and artificial sweeteners.
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How we research our recommendationsA good fit if…
People who want slow-digesting protein before bed or during long gaps between meals. Strength athletes and fitness enthusiasts looking to support overnight recovery. Those who enjoy a thick, filling shake and want added minerals in their protein supplement. Anyone pairing it with a fast-digesting whey post-workout.
Skip it if…
Anyone with a milk or soy allergy or intolerance. Drug-tested athletes who require a named, audited certification such as Informed Choice or NSF Certified for Sport. Those avoiding artificial sweeteners (acesulfame potassium, sucralose). Anyone seeking fast post-workout protein or a vegan/dairy-free option.
What actually matters
Protein source: 100% micellar casein, the intact native form that digests slower than whey. It forms a gel in the stomach and releases amino acids gradually, making it distinct from calcium caseinate, which does not behave the same way.
Macros per ~34g serving (Chocolate Supreme): 24g protein, 120 calories, 1g fat (0.5g saturated), 3-4g carbohydrates, 1g dietary fiber, 1-2g sugar, 0g added sugars. Values vary slightly by flavor.
Mineral content per serving: 500mg calcium, 85mg magnesium (20% DV), 11mg zinc (100% DV). Higher mineral density than most whey or plant protein powders at this serving size.
Allergens and additives: Contains milk and soy (soy lecithin as emulsifier). Sweetened with acesulfame potassium and sucralose. Contains a gum blend (guar, acacia, xanthan) that may cause digestive discomfort in sensitive individuals.
Texture is intentionally thick: micellar casein gels in liquid, producing a noticeably thicker shake than whey or plant proteins. The manufacturer recommends 8-10 oz of liquid for a pudding-like consistency and 12-14 oz for a thinner shake.
Third-party testing: described as 'banned substance tested' on the manufacturer page, but Gold Standard 100% Casein is not listed under a named Informed Choice or NSF Certified for Sport program. Drug-tested athletes should verify independently.
Suggested use per manufacturer: mix one scoop in 8-14 oz of cold water or milk 30-60 minutes before bed, or any time to supplement daily protein intake. Intended as part of a balanced diet and exercise program.
Available in four flavors (Chocolate Peanut Butter, Chocolate Supreme, Cookies and Cream, Creamy Vanilla) in 25-serving (1.87 lb) and 53-serving (3.97 lb) sizes from Optimum Nutrition.
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Sources, not guesswork
Published October 11, 2026. Consult the linked sources for current specifications. This is an editorial shortlist, not a verified Amazon bestseller or search-volume ranking.
Optimum Nutrition — Gold Standard 100% Casein product page (manufacturer)ProteinPowder.com — Optimum Gold Standard Casein review (independent)