Whey Protein Isolate: What It Is and How to Use It

EnergyFirst sells whey protein, so read this with that in mind. This article covers what whey protein isolate is, what makes it a high-quality protein, and how to use it sensibly.

What whey is

Milk contains two families of protein. Casein makes up about 80 percent and digests slowly. Whey is the other 20 percent: the protein fraction of milk that stays in the liquid when milk is made into cheese. Whey protein powders are made by filtering that liquid to separate the protein from the lactose, fat and minerals.

How far the filtering goes decides what you get. Whey protein concentrate ranges from about 34 to 80 percent protein, with the rest mostly lactose and fat. Whey protein isolate is filtered further, to about 90 percent protein, with very little lactose and fat left. We explain why isolate is worth paying for in a separate article.

Protein quality and leucine

Whey is a complete protein: it contains all nine essential amino acids, the ones your body cannot make. It is digested and absorbed quickly, and it scores at or above 1.0 on DIAAS, the current measure of protein quality, which means essentially all of it is usable.

The amino acid that matters most for muscle is leucine. It acts as the signal that switches on muscle protein synthesis, and that signal is strongest when a meal delivers roughly 2 to 3 g of leucine. Whey is about 10 to 11 percent leucine, so a 25 g serving of whey protein gives roughly 2.5 g. That is more leucine per gram of protein than most other common protein sources, which is why whey is the reference protein in so much of the research. We compare it with the alternatives in Whey vs. Casein, Soy, Pea and Egg.

Why isolate

Because isolate is about 90 percent protein, more of each scoop is the thing you are buying it for. The low lactose content means most people who are sensitive to lactose tolerate it well. The low fat content keeps the calories down, so a scoop is mostly protein and little else.

How much protein to aim for

Our target is about 0.85 g of protein per pound of bodyweight a day, which is about 1.9 g per kilogram. At 175 lb that is about 150 g a day, and the same is true at 80 kg (176 lb). Go toward 1 g per pound if you are losing weight, over 65, training hard or taking a GLP-1 medication. The research behind those numbers is in How Much Protein Do You Actually Need Per Day?

Spread that across three or four meals, each with 30 g or more. Most people fall short at breakfast, and that is where a scoop of whey isolate does the most good. A typical breakfast carries around 10 g of protein; a 20 g scoop with it brings the first meal of the day to 30 g without cooking anything extra. After training, and mid-afternoon in place of something sweet, are the other two places a shake fits well.

Food should still do most of the work. Use whey to close the gap on the days when food does not get you there.

Who should be careful

Whey is a dairy protein. If you have a true milk protein allergy, isolate is not a workaround, because the allergen is the protein itself. Anyone with reduced kidney function should set a protein target with their doctor rather than from a label.

Our whey protein isolate

EnergyFirst ProEnergy is a grass-fed whey protein isolate with 20 g of protein per scoop, in Ultimate Vanilla, Chocolate Decadence and Natural Unflavored.