Which whey protein should I buy?
Concentrate, unless milk sugar upsets you. Then try isolate, or clear whey if you’d like a squash-like drink. But in one trial, pre-digested whey built no more muscle or strength than plain concentrate.
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Which whey protein powder should I buy?
Plain whey concentrate, if milk agrees with you. Whey is one of the two main proteins in cow’s milk, about 20% of its protein. Concentrate keeps more of the milk sugar (lactose) and fat.
Does milk give you tummy pain, wind or bloating? That can be lactose intolerance. Isolate has most of the lactose filtered out, so people who are lactose intolerant can often take it.
| Type | What’s in it | Suits |
|---|---|---|
| Concentrate | Sports ones are usually 70 to 80% protein. More lactose and fat. | Most people who are fine with milk. |
| Isolate | Over 90% protein. About 0.5% lactose and 0.5% fat. | Often fine for people who get symptoms from milk sugar. |
| Hydrolysed | Whey broken into tiny pieces, so it gets into the blood faster. | No extra muscle or strength in one 8-week trial. |
| Clear whey | Isolate made into a clear, sharp drink, like squash. | People who don’t like milky shakes. |
Sources: ISSN; Hoffman 2004; Lockwood 2017; Best 2025
Pick the type that sits well in your stomach. Then compare tubs by grams of protein per serving.
Is whey protein isolate better than concentrate?
Purer, yes. Better for muscle, not shown. We found no trial that tested the two against each other for muscle.
Think of isolate as concentrate filtered for longer. More filtering takes out lactose and fat, so isolate is over 90% protein. But concentrate keeps more of milk’s other active parts.
What matters more is how much protein you get at a time. Sports nutrition experts at the ISSN suggest 20 to 40 g, or 0.25 g for each kg you weigh. At 80 kg, that’s 20 g.
- Below 20 g per servingLess than the ISSN suggests.
- 20 up to 40 g per servingISSN: 20 to 40 g at a time.
- Above 40 g per servingAbove the ISSN amount.
Source: ISSN
Space your servings every 3 to 4 hours. For your total a day, see how much protein to build muscle.
What is clear whey protein?
It’s whey isolate made into a thin, sharp drink. Isolate is used because it dissolves well in acidic drinks.
From milk to clear whey
- 1
Milk
Whey is the watery part left when milk is made into cheese.
- 2
Filter
Filtering takes out lactose and fat.
- 3
Isolate
Over 90% protein is called an isolate.
- 4
Clear drink
Made very acidic, the isolate stays clear.
Sources: Hoffman 2004; ISSN; Zaitoun 2026
Some taste a bit soapy. Lab tests traced it to natural fats from milk that you only taste in acidic drinks. If one tastes soapy, try another flavour or brand.
Is hydrolysed whey protein worth it?
Probably not for muscle. That pre-digested whey from the top of the page is hydrolysed whey.
It’s whey broken into tiny pieces with gut enzymes before you drink it. Those pieces reach the blood faster.
In one trial, 56 trained men lifted for 8 weeks. They took 30 g twice a day of concentrate, hydrolysed whey or a carb drink. Everyone gained muscle and similar strength.
Hydrolysed whey may have helped fat loss: body fat fell by about 6%, while the carb drink group gained fat. The authors found no other advantage. Two authors worked in the supplement industry, and it’s one small trial.
So your training does most of the work. See our guide to building muscle.
How do I choose the best whey protein?
Ignore the brand and the size of the tub. Read the back.
Five checks on a whey protein tub
- Find the grams of protein per serving, and look for 20 to 40 g.
- Read the first ingredient. UK lists start with the main one by weight, so whey should come first.
- Look for milk in the allergens, shown in bold or a different style.
- Check for “Excessive consumption may cause a laxative effect”. Tubs with over 10% polyols, a type of sweetener, must say it.
- Compete in a sport that tests for drugs? Use only batch-tested products (each batch checked for banned substances), and check the batch number before you use it.
Sources: ISSN; GOV.UK: ingredients; GOV.UK: warnings; UKAD
UK Anti-Doping says no supplement is certain to be free from banned substances.
Do you need a tub at all? The British Nutrition Foundation says most of us already eat more than enough protein. Food is better where you can.
Comparing whey with soy or pea? See the best protein powder for muscle gain.
Worried about heavy metals? See clean protein powder.
When to speak to a GP
For healthy people who train, reviews show no sign of kidney or liver harm from more protein. Speak to a GP if:
- You have kidney disease. People with kidney failure do better on less protein, so ask before you add a powder.
- Milk keeps giving you tummy pain, bloating, wind or diarrhoea after you eat it. The NHS says don’t cut foods out without a GP’s or dietitian’s advice.
- With those symptoms, you’ve had changes in your poo that are not usual for you (looser, more often, or constipation), blood in your poo, or tummy bloating and discomfort for 3 weeks, or you’re losing weight without trying.
- You think you may have a milk allergy. Isolate is low in lactose, but it’s still milk protein. See dairy-free protein powder.
Call 999 for a serious allergic reaction, if:
- your lips, mouth, throat or tongue suddenly swell
- you’re breathing very fast or struggling to breathe
- your throat feels tight or you’re struggling to swallow
- your skin, tongue or lips turn blue, grey or pale (on black or brown skin, this may be easier to see on the palms or soles of the feet)
- you suddenly feel very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do
Had a raised kidney result after starting whey? See does whey protein affect a blood test.