Wednesday, 24 July 2024

Protein Powder

Optimum Nutrition Casein Gold Standard 100% Protein Powder Review

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Optimum Nutrition Casein delivers 24 grams of slow-digesting protein and 9.6 grams of essential amino acids per serving, all for just 120 calories (140 calories if you choose the Naturally Flavored version).

So what exactly is casein protein, and how does the Optimum Nutrition powder compare to bestsellers from MuscleTech and MusclePharm?

In this review we’ll take a closer look at the ingredients, dosages, calorie levels, price, and customer feedback, to guarantee you only buy the best Casein protein for your budget. We’ve also compared the ON Casein to the unique time released Combat protein powder from MusclePharm, and the Phase 8 multi-phase 8-hour protein powder from MuscleTech.

Both of these products blend proteins from multiple sources, and deliver more protein per serving than Optimum Nutrition. So how has the ON Casein maintained its position as market leader, with over 2400 highly rated reviews on Amazon?

Optimum Nutrition Casein Ingredients

Optimum Nutrition Casein Ingredients

Optimum Nutrition faces some serious competition from MusclePharm when it comes to the best casein protein powder. A quick look at the macronutrient profile shows Combat 100% Casein (MusclePharm) has 3 g more protein, 1 g less carbs, and zero fat compared to Casein Gold Standard (Optimum Nutrition).

In fact, there’s really only one area where Casein Gold Standard beats MusclePharm Casein, and that’s in the cholesterol level (15 mg vs. 20 mg).

The micronutrient content shows MusclePharm Casein has more calcium (600 mg vs. 500 mg), less sodium (55 mg vs. 240 mg), and no soy, compared to Gold Standard Casein.

However, in terms of customer feedback and popularity, Optimum Nutrition Gold Standard Casein remains a market leader. Each scoop delivers more protein than Six Star Casein, with less carbs and fat than Kaged Muscle Kasein.

Benefits of slow digestion and Aminogen®

Because this is a casein protein powder, you can expect a slower digestion rate, making it the perfect choice for nighttime muscle support. The slower breakdown ensures your muscles keep receiving a flow of amino acids at a time when your body typically goes for hours without food.

In addition to the micellar casein protein, the ingredients label also shows cocoa, natural and artificial flavors, sucralose and acesulfame potassium as sweeteners, and soy lecithin to improve mixability.

Each scoop also contains Aminogen®, which is a patented enzyme system designed to increase BCAA retention levels, nitrogen levels in muscle, and overall amino acid plasma levels. In essence, Aminogen® improves protein digestion and increases the efficiency of amino acid absorption from the casein protein.

Each serving contains 9.6 g of Essential Amino Acids (EAAs), 10.3 g of Conditionally Essential Amino Acids (CAAs), and 4.1 g of Nonessential Amino Acids (NAAs). This includes nearly 5 grams of BCAAs (Leucine, Isoleucine, Valine).

Optimum Nutrition Casein Gold Standard 100% Protein Powder

O.N. Casein – Product Summary

  • Made Exclusively With Micellar Casein
  • 24 Grams of Slowly Digesting Protein Per Serving
  • Use Between Meals to Support Satiety and/or Before Bed as Your PM Protein
  • Nearly 5 Grams of Naturally Occurring BCAAs per Scoop
  • Made in GMP Certified ON Owned and Operated Facilities

When is the best time to take it?

Recommended use

Take Gold Standard Natural 100% Casein immediately before bed and in-between meals when delayed protein delivery is desired.

O.N. Casein vs. MusclePharm Combat

O.N. Gold Standard Casein
MusclePharm Combat
Protein: 24 g
Protein: 25 g
Carbohydrates: 3 g
Carbohydrates: 3 g
Fat: 1 g
Fat: 1.5 g
Calories: 120
Calories: 130
Protein density: 71%
Protein density: 81%
Container size: 1782 g
Container size: 2240 g
Serving size: 34 g
Serving size: 31 g
Cost per serving: $1.00
Cost per serving: $0.61

O.N. Casein vs. MuscleTech Phase-8

O.N. Gold Standard Whey
MuscleTech Phase-8
Protein: 24 g
Protein: 26 g
Carbohydrates: 3 g
Carbohydrates: 8 g
Fat: 1 g
Fat: 1.5 g
Calories: 120
Calories: 160
Protein density: 71%
Protein density: 62%
Container size: 1782 g
Container size: 2090 g
Serving size: 34 g
Serving size: 42 g
Cost per serving: $1.00
Cost per serving: $1.89

What flavors and sizes are available?

With a serving size of 33 grams, each tub provides you with either 27 or 54 servings. Following the recommendation of 2 servings per day, this is enough to last up to 4 weeks.

At the time of writing this review, the best value for money comes from the 4 pound tub. Each serving was priced at $1.00, compared to $1.18 per serving with the smaller 2 pound tub. That’s why we always recommend calculating the average cost per serving, across all sizes, before making a final buying decision.


  • Banana Cream
  • Chocolate Peanut Butter
  • Chocolate Supreme
  • Cookie Dough
  • Cookies and Cream

  • Creamy Vanilla
  • Mint Chocolate
  • Natural Chocolate
  • Natural French Vanilla
  • Strawberry

Save money with Amazon

If you’re looking to save money on your monthly protein powder order, you might want to consider the Amazon Subscribe & Save program.

Subscribe & Save allows you to unlock savings of up to 15% on a wide range of supplements, including Optimum Nutrition Casein.

You can save 5% with a subscription to 1 product, or save the full 15% by subscribing to 5 products, provided they’re all delivered to the same address. The delivery schedule can be set from monthly, up to once every 6 months.

Although 5 products might sound a lot, if you already supplement with a protein powder, multivitamin, creatine, BCAA, and glutamine, the savings can soon add up.

Who are Optimum Nutrition?

With over 30 years in the sports nutrition industry, Optimum Nutrition currently produces some of the bestselling sports nutrition products in the world. These have been designed to improve your strength and recovery, health and wellness, and help increase your protein intake, such as their Gold Standard 100% Whey.

To find out more about their protein powders, bars, ready to drinks, BCAAs, glutamine, pre-workout supplements, creatine, multivitamins, and weight loss products, we recommend our Optimum Nutrition buying guide. This includes a summary of the health benefits you can expect from each product, which sizes and flavors are available, and dosages for the top ingredients.

We’ve also added in-depth reviews and comparisons with other top rated nutrition companies, to guarantee you only buy the best supplement for your fitness goals.

Protein Powder Buying Guide

Review Overview

Overall Review Rating

4.5 / 5

At the time of writing this review, each 34 g serving of Optimum Nutrition Casein Gold Standard was priced at $0.96, based on buying the 2 pound tub. This was cheaper than the 4 pound tub, which was priced at $0.98 per serving.

So is this good value for money, and do we recommend buying Gold Standard Casein?

The price is a little higher than competing brands, some of whom deliver formulas that have more protein and less carbs.

For example, Dymatize Elite Casein was priced at $0.93 per serving for 25 g of protein and 2 g carbs, and MusclePharm Combat 100% Casein was priced at $0.90 per serving for 28 g of protein and 2 g of carbs. Each of these powders uses micellar casein, but only Optimum Nutrition has the Aminogen enzymes to improve digestion.

In terms of flavor, you’ll struggle to beat Optimum Nutrition. Even their Gold Standard Casein has 10 options to choose from, compared to 3 flavors for Dymatize, and 2 flavors for MusclePharm.

Gold Standard Casein is also backed by thousands of highly rated reviews on Amazon, with customers praising the great taste, affordable price, and fast shipping. Only a handful of reviews mention undissolved clumps when mixing, but this is usually avoided with a protein shaker and filter.

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