Whey Protein Powder

What is whey protein?

Whey is one of the two main proteins in milk, and casein is the other. Whey protein powder is whey that has been filtered to concentrate the protein and then dried, and how far it is filtered decides whether it is sold as a concentrate or an isolate.

Because it comes from milk, every whey product contains milk, which is one of the 14 allergens that must be emphasised within the ingredients list of pre-packed food. Check the label for milk and for anything else that matters to you, such as soya or gluten.

Whey concentrate, isolate or blend: what's the difference?

The main difference is how much of the powder is protein. The American Dairy Products Institute specification defines whey protein isolate as at least 89.5% protein on a dry basis, and anything below that as a concentrate, with the common WPC 80 grade at a minimum of 79.5%.

These figures are for the raw ingredient, not the finished tub: flavourings and sweeteners lower the protein per 100g. Compare concentrates, isolates and blends on the nutrition panel. "Concentrate, isolate and blends are marketed differently, and customers can end up paying considerably more without fully understanding what they're getting," says Andy Arshad, who runs SupplementHQ. "A well-known brand isn't necessarily the best-value option, and a cheaper tub isn't necessarily the most economical."

How much protein do you need a day?

The British Dietetic Association says people who don't exercise need about 0.75g of protein per kg of body weight a day, and athletes in strength and endurance sports around 1.4 to 2.0g per kg. For a 70kg adult, that is about 53g a day without regular exercise, or 98g to 140g for a strength athlete.

EFSA sets the adult reference intake at 0.83g of protein per kg of body weight a day, says there isn't enough data to set an upper limit, and considers twice that amount safe for adults. If you have a medical condition, speak to your GP or a dietitian before making big changes to your diet.

How much whey protein per shake?

Most people compare servings of 20g to 25g of protein, because that is roughly where the research shows the effect levelling off after training. A 2009 study in young men found that muscle protein synthesis (the process of building new muscle protein) after resistance exercise was maximally stimulated at 20g of protein, out of doses from 0g to 40g.

That study used egg protein in a small group of young men, so read it as a guide rather than a rule. It is one reason we compare products on the cost per 25g of protein: it is close to a typical serving and works for every tub size.

Do you need whey protein?

No. The British Dietetic Association says a healthy, balanced diet should provide enough protein to meet any increased requirements, and that supplements will not compensate for poor food choices but may be helpful in certain situations.

Whey is a convenient way to add protein when food alone is hard to fit in. Where a product is at least a source of protein, the authorised claims are that protein contributes to a growth in muscle mass and that protein contributes to the maintenance of muscle mass. Our guide to what supplements you actually need covers the bigger picture.

Is whey protein OK if you're lactose intolerant?

It depends on the product and how much lactose you can manage. The NHS describes lactose intolerance as getting symptoms, such as tummy pain, after eating food containing lactose, and the ADPI specification allows far less lactose in isolate (4%) than in WPC 80 concentrate (13%).

A milk allergy is different: the NHS says a food allergy can be life threatening, and whey is a milk protein, so it is not a way round a milk allergy. See vegan protein instead, and don't cut foods out without advice from your GP.

How do you compare whey protein on value?

Work out the cost per 25g of protein: divide the price by the total protein in the tub (servings × protein per serving), then multiply by 25. This puts different tub sizes and scoop sizes on the same footing.

How to compare value (example figures, not real products): Tub A costs £30 for 1kg, with 24g of protein in a 30g scoop. That is 33 servings and 800g of protein, or about 94p per 25g. Tub B costs £45 for 2kg, with 30g of protein in a 40g scoop: 50 servings, 1,500g of protein, or 75p per 25g. Tub B costs 50% more on the shelf but about 20% less per 25g of protein.

"When we compare products from different brands and wholesalers, serving sizes, protein concentrations and the number of servings per tub vary considerably," says Andy. "Two products can look similarly priced, but once you calculate the actual cost per 25g of protein, the value can be quite different."

Which is the best whey protein in the UK?

The best whey protein for you gives the protein you want per serving, in a type that suits your digestion and diet, at a sensible cost per 25g. A bigger brand name, more ingredients or a higher price doesn't automatically make a product better.

"The amount of protein on the front of the packaging doesn't always tell you which product offers the best value," says Andy. Start with the nutrition panel and the ingredients list (our guide to reading a supplement label shows how), then compare across all protein powder.

We sell the products on this page. That's our commercial interest, and it's why we show the evidence alongside them. This page is general information for adults, not personalised medical advice. Food supplements should not replace a varied, balanced diet.

Written by Andy Arshad, SupplementHQ. Last reviewed 11 October 2026.