Whey protein vs whey isolate: what's the difference?

Choosing between whey protein vs whey isolate? From the taste and the calories to the protein content and the price – here are all the differences

Close up on man's hand scooping protein powder into flask
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Whey protein is a popular supplement that can be helpful if you’re trying to build muscle and strength. It’s found in milk and separated out in its liquid form during the cheese-making process. It contains all nine essential amino acids, making it a complete protein source. It is one type of dairy protein, the other being casein.

There are different types of whey protein available, including whey protein concentrate and whey protein isolate. The isolate version is a highly filtered product that removes a higher proportion of fat, carbohydrates and lactose. 

For some people, whey isolate is the best choice, but it’s also more expensive. Here, Fit&Well explains the production process, protein content, pricing differences and benefits.

Expert input from
Theresa Gentile
Expert input from
Theresa Gentile

Theresa Gentile, MS, RDN, CDN, Brooklyn, N.Y., is a National Media Spokesperson for the Academy of Nutrition and Dietetics. She is the coordinator of the home enteral nutrition program at Maimonides Medical Center and owns a nutrition consulting practice where she focuses on cardiac health and weight management by improving women's metabolisms. She previously served as an adjunct faculty member at CUNY Brooklyn College and has earned the Distinguished Dietitian of the Year Award from the Greater New York Dietetic Association. Gentile earned undergraduate and master’s degrees from CUNY Brooklyn College. 

How is whey protein isolate made  

Whey protein supplements are usually sold in powdered form, but it starts as a liquid by-product of cheese-making. 

Theresa Gentile, MS, RDN, CDN, National Spokesperson for the Academy of Nutrition and Dietetics explains: “Whey is the liquid part of milk in the cheese-making process and is composed of the eight proteins found in milk. In the process to make cheese, enzymes are added to milk that cause it to curdle, separating the liquid whey from the solid curds. The liquid part is the whey, which contains lactose and fat. Manufacturers pasteurize and dry the whey to form a powder.” 

Whey isolate undergoes more processing than whey concentrate, as it has most—if not all—of its lactose content removed. Flavorings are also often added to the powder before it hits the shelves. 

Is whey isolate better than whey protein? 

Whey concentrate and isolate are both high in protein, but the isolate powder contains slightly more protein per gram. 

According to Gentile: “Whey protein concentrate has a protein concentration of 70-80% and contains some lactose [milk sugar] and fat. Whey protein isolate is the concentrate minus some of those carbohydrates and fat—it 'isolates' the protein portion, the whey. This results in a product whose protein concentration is about 90% and is absorbed faster than whey protein concentrate.”

Absorption speed affects how quickly your body can use the protein to repair and build your muscles, however it’s unlikely that the difference in absorption speeds will affect your overall muscle growth. 

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Pricing and availability 

Since whey protein isolate requires more steps and filters out a larger amount of non-protein material, it’s also more expensive. A variety of other factors will influence the price of whey protein powder as well, including whether the milk is originally grass-fed, cold-processed and more. At the time of writing, prices range from $1 or less for concentrate to $2.50 a serving and higher for isolate.

Blends of whey protein concentrate and isolate are also available, creating a middle ground that comes with a mid-level price. Ultimately, the best protein powder you can buy is one you enjoy, so find a brand that has a flavor and consistency that you enjoy. 

Whey protein vs whey isolate: verdict

If you have trouble reaching your protein intake goal and need a supplement to help you get there, any type of whey protein will be suitable. If getting more protein into your diet without additional calories and fat or triggering any digestive issues from lactose, whey isolate may be the best choice. 

However, whey protein is more widely available, costs less and is often sold in various flavors. Unless you struggle with lactose or are on a strict diet, the slight difference in calories and higher protein concentration of isolate is typically insufficient to warrant the additional cost. 

See our round-up of the best protein powders for weight loss, if you're looking for brand suggestions.

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What are the benefits of whey protein? 

1. Whey can help you build muscle

Both whey protein and whey isolate come with a host of benefits. 

Theresa Gentile, a national spokesperson for the Academy of Nutrition and Dietetics, says that dietary whey supplementation, paired with resistance training, can increase muscle protein synthesis. 

One placebo-controlled study found that ingesting whey protein before and after exercise increased muscle strength and size. That said, a lot of people can get sufficient protein through food, so it’s not always necessary to purchase a supplement.  

2. Whey can be absorbed fast

Whey’s absorption rate has been estimated at approximately 10g per hour. Research published in the Journal of the International Society of Sports Nutrition states it would take just two hours to fully absorb a 20g dose of whey protein. The same research states it would take around seven hours for complete absorption of an omelet containing the same 20g of protein. 

Note that these results can change depending on what you pair with your whey protein supplement. Adding fats or fiber will significantly slow absorption rates.

But what has a slower absorption rate, whey protein or whey isolate? “Whey protein,” Gentile says. “It’s because of its higher calorie and fat content; it is absorbed slower than the other forms of whey.”

3. Whey isolate can be taken by those who are lactose-intolerant 

 Due to the additional manufacturing process whey isolate undergoes, it contains little to no lactose. This makes it a popular choice for those who are lactose intolerant. And, while whey protein doesn’t have masses of lactose, it could cause “bloating and/or stomach issues for those sensitive to lactose,” says Gentile.

Becks Shepherd

Becks is a freelance journalist and writer with more than 7 years of experience in the field. She writes health and lifestyle content for a range of titles including Live Science, Top Ten Reviews, Tom’s Guide, Stylist, The Independent, and more. She also ghostwrites for a number of Physiotherapists and Osteopaths. 

Health has been a big part of Becks’ lifestyle since time began. When she’s not writing about the topic of health, she’s in the gym learning new compound exercises. And when she’s not in the gym, she’s most probably reading. 

With contributions from