What Does Whey Protein Do?

About whey protein

Whey is one of the two proteins found in milk, the other being casein. When milk is separated during cheesemaking, the liquid left behind is whey. That liquid is filtered, dried and turned into the powder you buy.

Whey is a complete protein, meaning it contains all nine essential amino acids — the ones the body cannot make and has to obtain from food. It is also naturally high in the three branched chain amino acids: leucine, isoleucine and valine.

The three forms of whey

Whey protein concentrate is the least processed form, typically 70–80% protein by weight, with the remainder made up of lactose, fat and minerals. It is the most affordable and generally the best tasting.

Whey protein isolate is filtered further, usually to 90% protein or above. Most of the lactose and fat is removed along the way, which is why isolates suit people who find concentrate hard going.

Whey protein hydrolysate has been partially broken down using enzymes before you drink it, producing shorter chains of amino acids called di- and tri-peptides. It is the most expensive of the three and usually the most bitter.

Many products blend all three, using the faster and slower fractions together.

How whey is used

Whey digests quickly compared with casein, which thickens in the stomach and takes considerably longer to break down. That difference in digestion rate is why whey is commonly taken around training and casein before bed.

A typical serve of 25 to 35 grams of powder delivers somewhere between 20 and 30 grams of protein, depending on the form. Check the label rather than assuming — the gap between a 70% concentrate and a 90% isolate is significant when you work it out per scoop.

Reading the label

Two things are worth checking on any tub.

Protein per serve against serving size. Divide grams of protein by grams of powder. That percentage tells you more than the marketing on the front.

The ingredient list order. Ingredients are listed by weight. If whey protein isolate appears first, isolate is the main protein source. If it appears after concentrate, it is not.

Whey and dietary protein

Whey protein is a food, and it supplements dietary protein rather than replacing it. Whole foods — meat, eggs, dairy, legumes — provide protein alongside other nutrients that a powder does not. Most people use protein powder for convenience: when a meal is not practical, or when hitting a daily protein target through food alone is difficult.

If you have a medical condition, are pregnant or breastfeeding, or take prescription medication, speak to your doctor or pharmacist before adding any supplement to your diet.