Whey protein vs whey isolate: dietitians explain the difference

There are so many types of protein powders on the market, it’s no wonder people are asking: whey protein vs whey isolate—what’s the difference?

Let’s start with the basics and explain what whey protein is. Also known as whey concentrate, whey protein is made from the watery bit of milk that separates from the curds when making cheese. This can be dried and turned into the protein powder that you see stocked on shelves.

Whey isolate is a product that's filtered even further to remove a higher amount of fat, carbohydrates and lactose (milk sugar) so it’s a leaner protein source.

Kylie Bensley, registered dietitian and founder of Sulini Nutrition, told Fit&Well: "Whey protein isolate is higher in protein and lower in fat and carbs than concentrate. It also contains less lactose so may be more appropriate and tolerable for people with lactose intolerance and sensitivities, but isolate does tend to be more expensive."

Kylie Benson

Kylie Bensley is a highly regarded clinical dietitian with a wealth of expertise in nutrition. With an unwavering dedication to patient care, Bensley has spent over a decade working in renowned medical facilities in Boston and Cambridge, MA. Throughout her extensive career, she has provided invaluable guidance to patients recovering from surgery, establishing herself as a leading and trusted authority in the field.

Whey concentrate vs whey isolate: the real differences

Whey concentrate and isolate are both a by-product of cheese-making but the latter is more filtered. As mentioned above, isolate has a higher protein content with less fat, carbohydrate and lactose.

According to Bensley: "Whey protein can offer anywhere between 10-15% protein content per serving with over 50% lactose and almost 2% fat. Whey protein isolate contains over 90% pure protein content with under 1% lactose or milk fat."

Theresa Gentile, spokesperson for the Academy of Nutrition and Dietetics, also told Fit&Well: "Whey protein isolate essentially 'isolates' the protein portion, which results in a product that is absorbed faster than concentrate."

However, Gentile says the speed at which the body absorbs protein is unlikely to affect overall muscle growth, so don't let this dictate which protein powder you buy.

Expert input from

Expert input from

Theresa Gentile

Theresa Gentile, MS, RDN, CDN, is a national 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. 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.

Because whey isolate has a more complex filtering process, it tends to be more expensive. Other factors could also impact the price—including whether the milk is cold-pressed or from grass-fed cows. Blends of concentrate and isolate are also available at a slightly cheaper price.

How exactly 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. 

"In the process to make cheese, enzymes are added to milk that cause it to curdle, separating the liquid whey from the solid curds," explains Gentile. "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.

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. The body can absorb isolate at a quicker rate, but this isn't likely to affect the speed of your muscle growth.

To be honest, the best protein powder you can buy is one you enjoy drinking and cooking with, so opt for a brand that has a flavor and consistency you like. See our guide to the best protein powders for weight loss to browse some options.

Whey protein vs whey isolate: verdict

If you’re trying to build muscle or reach your protein goals on the go, then both concentrate and isolate are good options. However, if you have a sensitive tummy, digestive issues, or are on a calorie deficit, then whey isolate could be the best choice.

Whey protein is more widely available and more budget-friendly, and often comes in a wider variety of flavors. Unless you are lactose intolerant or on a restricted diet, the small difference in calories and higher protein content of isolate might not be enough to warrant the steeper price tag.

What does protein powder do?

We need protein for muscle growth as well as to repair tissue and make enzymes and hormones. Research published in the British Journal of Sports Medicine found that taking protein powder could improve muscle size and strength in healthy adults who do resistance training, such as weight lifting.

Most people can get enough protein from their diet, however, so it’s not always necessary to take supplements to achieve hypertrophy (muscle growth). If you are trying to build muscle, make sure you read up on the progressive overload principle and do regular strength training.