Whey Protein Compared: What's Actually in Each Scoop

Quick Verdict

Not all protein powders are equal — even when they claim similar protein per serving. Myprotein Impact Whey and Bulk Pure Whey offer the best value per gram of actual protein. PhD Diet Whey has the lowest protein percentage at ~65%, meaning a third of each scoop is filler. Applied Nutrition ISO-XP delivers the cleanest profile as an isolate but at a higher price.

Product Overview

Factor	Myprotein Impact	Bulk Pure Whey	ON Gold Standard	PhD Diet Whey	AN ISO-XP
Type	Concentrate	Concentrate	Blend (concentrate + isolate)	Blend + extras	Isolate
Price (1kg)	~£20	~£18	~£30	~£22	~£28
Servings per 1kg	40	33	33	25	40
Cost per serving	~£0.50	~£0.55	~£0.91	~£0.88	~£0.70

Nutritional Comparison (Per Serving)

Per Serving	Myprotein Impact	Bulk Pure Whey	ON Gold Standard	PhD Diet Whey	AN ISO-XP
Serving size	25g	30g	30.4g	40g	25g
Protein	21g	23g	24g	26g	22g
Calories	103 kcal	119 kcal	121 kcal	170 kcal	93 kcal
Fat	1.9g	2g	1.8g	3.5g	0.3g
Carbs	1g	1.5g	1.5g	9g	0.5g
Sugar	1g	1g	1g	5g	0.4g
Protein %	84%	77%	79%	65%	88%

The Protein Percentage Test

This is the number that matters most. Divide protein by serving size and multiply by 100.

Applied Nutrition ISO-XP leads at 88% — expected for an isolate. Myprotein Impact Whey is impressively high for a concentrate at 84%. PhD Diet Whey scores just 65%, meaning 35% of every scoop is carbs, fat, thickeners, and added ingredients like CLA and L-carnitine.

When PhD Diet Whey claims 26g protein, it needs a 40g scoop to get there. Myprotein delivers 21g from just 25g of powder. You are paying for significantly more filler with PhD.

Real Cost Per Gram of Protein

Brand	Cost per serving	Protein per serving	Cost per gram of protein
Myprotein Impact	£0.50	21g	£0.024
Bulk Pure Whey	£0.55	23g	£0.024
ON Gold Standard	£0.91	24g	£0.038
PhD Diet Whey	£0.88	26g	£0.034
AN ISO-XP	£0.70	22g	£0.032

Myprotein and Bulk are virtually tied at 2.4p per gram of protein — nearly 40% cheaper than ON Gold Standard per gram.

Leucine Content: The Muscle Trigger

Leucine is the amino acid that triggers muscle protein synthesis. You need roughly 2.5g per meal to maximise the response.

Brand	Leucine per serving (approx)	Hits 2.5g threshold?
Myprotein Impact	~2.1g	Close — have with leucine-rich food
Bulk Pure Whey	~2.3g	Close
ON Gold Standard	~2.5g	Yes
PhD Diet Whey	~2.2g	No — despite higher total protein
AN ISO-XP	~2.4g	Close

ON Gold Standard edges ahead here because its isolate fraction has a slightly higher leucine percentage. For the others, pairing your shake with a leucine-rich meal (eggs, chicken, dairy) bridges the gap easily.

Concentrate vs Isolate vs Hydrolysate

Concentrate (~80% protein) — the standard. Retains some fat and lactose. Cheapest to produce. Fine for most people.

Isolate (~90% protein) — extra filtration removes nearly all fat and lactose. Worth it if you are lactose intolerant or want minimal calories around protein. Not worth a 2x price premium for general use.

Hydrolysate — pre-digested for faster absorption. Research shows negligible real-world benefit for muscle building. Almost never worth the premium.

What the Labels Don’t Highlight

Amino spiking was historically an issue where manufacturers added cheap amino acids (glycine, taurine) to inflate the protein number on the label. Reputable brands like those listed here have largely moved away from this, but it is worth checking ingredient lists for standalone amino acids listed before flavouring.

Thickeners and gums (xanthan gum, guar gum) affect texture and mixability but are nutritionally irrelevant. PhD Diet Whey and ON Gold Standard use more of these for a thicker shake. Myprotein mixes thinner but that is not a quality issue.

Who Each Product Suits

Myprotein Impact Whey — best overall value. High protein percentage, low cost, wide flavour range.

Bulk Pure Whey — matches Myprotein on value with slightly larger servings. Good alternative.

ON Gold Standard — the reliable mid-range choice with strong leucine content and good mixability. You pay more but get a polished product.

PhD Diet Whey — misleading name. It is not a superior diet product — it is a lower-protein blend with added CLA and L-carnitine at sub-effective doses. Skip it.

AN ISO-XP — best for those wanting a pure isolate without the premium price of ON Isolate. Great protein percentage and low calorie.

Where to Buy

For more on choosing the right protein, see our whey protein guide.