Guide

Whey protein: what it's for

Whey protein is milk protein in a handy tub. It's not a drug and not magic: it helps you hit your protein when food alone doesn't get you there.

Updated October 16, 2026

What it is

When milk is made into cheese, liquid whey is left over. It contains protein — quickly digested and with the full set of essential amino acids. That protein gets filtered out and dried into a powder. That's all "sports nutrition" is here.

It's closer to milk and cottage cheese than to pills. Your muscles can't tell protein from a shaker from protein from chicken — what matters to them is how much arrives over the day.

When it's handy

When food alone doesn't get you to your target. For building muscle, aim for about 1.6 g of protein per kg of bodyweight a day (the Morton et al. 2018 meta-analysis). For 80 kg that's almost 130 g, and not everyone wants to eat that much meat and cottage cheese.

No time for a proper meal — a shake takes a minute.
Dinner is still hours away after training.
You're vegetarian but eat dairy.
Your appetite is small, and a bulk needs more.

If you already hit your target with food, protein powder adds nothing. Work out your target in the protein calculator.

Isolate, concentrate, hydrolysate

Concentrate — the most common and the cheapest. It has a little lactose and fat and slightly less protein per serving.
Isolate — filtered further: more protein, almost no lactose or fat. It costs more. Pick it if milk upsets your stomach.
Hydrolysate — the protein is already partly broken down. The most expensive; no proven advantage for muscle growth.

For building muscle the difference between them is small. Take concentrate if you handle milk fine and isolate if you don't. If you can't do dairy at all, there are plant proteins — pea, soy, rice, ideally a blend.

How much to take

One scoop usually gives 20–30 g of protein — check the nutrition label, not the front of the tub. The ISSN position stand (Jäger et al., 2017) puts a meal at 20–40 g of protein, so one or two scoops is already a serving.

How many servings a day depends on how much you're short. Add up the protein from your regular food, subtract it from your target — the difference is your protein powder. Most often that's one serving a day, sometimes two. Don't live on shakes: food brings fibre, vitamins and the stuff that keeps you full, not just protein.

When to take it

Whenever it's convenient. The idea that you must drink it within 30 minutes of training or it's all wasted didn't hold up: in the review by Aragon and Schoenfeld (2013), the window around training turned out to be wide — what matters more is protein over the day and how much you ate before and after.

Handy moments: after training if your next meal is a couple of hours away; as a snack; at breakfast when it's low in protein. More on eating around training is in the guide on what to eat before and after a workout.

It's not magic

In the Morton meta-analysis, adding protein to training increased muscle and strength gains, but only a little, and mostly in people who weren't eating enough of it. Training with progressive overload is what makes you grow; protein is the building material.

If the tub says "10 lb of muscle in a month", that's marketing. If the weight on the bar has stalled, the cause is almost never your protein brand: more often it's sleep, calories or the program. Start with the guide on supplements that work.

How to pick a tub

Look at the grams of protein per serving and the serving size — that's how you compare price per 100 g of protein, not per tub.
Ingredients: protein listed first, no "proprietary blends" that hide how much of what is inside.
Third-party lab testing — it matters if you compete and get drug tested.
Taste matters more than you'd think: protein you hate drinking will sit on the shelf.

"Growth" extras in protein powder — added amino acids, boosters — raise the price, not your muscle.

Common questions

Is it bad for your kidneys? In healthy people, normal amounts of protein haven't shown harm. If your kidneys are sick, see a doctor first.

Is it for women too? Yes, it's just protein. You can't get "too bulky" from protein powder.

Can I take it without training? As food, sure, but training is what makes you grow, not the powder.

Should I take it before bed? You can; the ISSN names 30–40 g of slow protein before sleep as a handy way to close the day's gap — casein or cottage cheese fit that better than whey.

Log your workouts — I'll show whether your weights go up. That's the answer to whether you're getting enough protein, tub or no tub.

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