Protein Powder UK Guide: Whey, Casein, Pea, or Collagen — Which Is Best?

Protein powders are the most used supplement in the world — and also one of the most confusing. Whey, casein, pea, soy, hemp, egg white, collagen — the choice is overwhelming. Here's a clear breakdown of what each does, who it's for, and when to take it.

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Why protein intake matters

Most UK adults fall short of optimal protein intake for muscle retention, particularly as they age. The RDA of 0.8g/kg bodyweight is the minimum to avoid deficiency — it's not the optimal for muscle synthesis or body composition.

Research consensus: For muscle gain or retention, target 1.6–2.2g protein per kg bodyweight per day.

For a 75kg person, that's 120–165g of protein daily — difficult to hit from whole food alone.

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Whey protein: the gold standard for muscle building

What it is: A byproduct of cheese production. Highly bioavailable, complete amino acid profile, extremely high in leucine (the key trigger for muscle protein synthesis).

Types: - Whey concentrate: 70–80% protein, some lactose and fat. Cheapest option, fine for most. - Whey isolate: 90%+ protein, minimal lactose. Better for lactose-sensitive people. - Whey hydrolysate: Pre-digested, fastest absorption. Most expensive. Minimal advantage over isolate for most.

Best for: Post-workout muscle repair and growth.

Timing: Within 2 hours post-workout. Also fine any time of day.

Dose: 25–40g per serving.

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Casein protein: slow and steady

What it is: The main protein in cow's milk. Forms a gel in the stomach, releasing amino acids over 5–7 hours (vs 1–2 hours for whey).

Best for: Before bed — maintains protein synthesis overnight, reduces muscle breakdown during the fasting period of sleep.

Evidence: Studies show casein before bed improves overnight muscle protein synthesis. Works best in a recovery context.

Not ideal: Post-workout (too slow for immediate repair needs).

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Pea protein: the best plant option

What it is: Extracted from yellow split peas. Complete amino acid profile (though lower in methionine than whey).

Evidence: Multiple RCTs show pea protein comparable to whey for muscle gain when consumed at adequate doses. It's not quite as anabolic, but close enough that total protein intake matters more than source.

Best for: Vegans, people with dairy allergies, or those who prefer plant-based nutrition.

Tip: Combine with rice protein for a more complete amino acid profile that better approximates whey.

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Collagen protein: not for muscle building

What it is: Derived from animal connective tissue (bones, skin, hides). Rich in glycine, proline, and hydroxyproline — not a complete protein.

What it doesn't do: Build muscle. Collagen is very low in leucine and BCAA content. Do not use as a whey replacement.

What it does do: Supports skin elasticity, joint cartilage health, and tendon repair. Evidence supports 10–15g daily with vitamin C for joint and skin benefits.

Best for: Skin, joints, gut lining — not muscle protein synthesis.

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Hemp protein: whole-food nutrition, not a muscle builder

What it is: Ground hemp seeds. Complete amino acid profile, but only 50–70% protein content and high in fibre.

Best for: Adding plant-based protein to smoothies as part of a whole-food approach. Not ideal as a primary protein supplement.

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How to choose

| Your goal | Recommended | |-----------|-------------| | Build muscle (omnivore) | Whey isolate or concentrate | | Overnight recovery | Casein | | Build muscle (vegan) | Pea + rice blend | | Joint and skin health | Collagen peptides | | Dairy-free muscle building | Pea isolate | | General protein top-up | Any complete protein |

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Red flags to avoid

- Proprietary blends (you can't see individual ingredient doses) - Amino acid "spiking" (glycine or taurine added to inflate protein count cheaply) - Artificial sweeteners if you're sensitive (sucralose can cause GI issues at high doses) - Proprietary blend labels that don't show grams of protein per amino acid

Always check that the label shows total protein per serving (not total amino acid blend) and that it comes from third-party tested manufacturers.