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Whey protein

Whey concentrate (~80% protein) or isolate (~90%) — isolate if lactose-sensitive; look for ≥2.5 g leucine per 25 g serving and third-party testing (Informed Sport / NSF)

StrongReal, but too small for your device to notice

Strong

Several good studies agree

Why this rating

49 RCTs with 1863 participants, plus a separate recovery meta-analysis, converge on a modest but robust effect with a clear dose-response breakpoint. The honest caveat: whey did nothing for CK or soreness at any timepoint — the benefit is function and mass, not perceived recovery.

3
studies
62
experiments
1,863
people (largest study)
2
kinds of study
In short

Over a training block it adds a little muscle (about a third of a kilo) and a couple of kilos to your best lift, and your strength comes back faster in the three days after a hard session.

The bottom line

Adds 0.30 kg of fat-free mass (95% CI 0.09 to 0.52) and 2.49 kg to 1RM strength (95% CI 0.64 to 4.33) over a training block, and speeds strength recovery at 72 h post-exercise (ES 0.7, 95% CI 0.2 to 1.3).

How it works

Rapid aminoacidemia with a high leucine fraction triggers mTORC1-mediated muscle protein synthesis; the acute dose threshold for maximal stimulation is ~0.25 g/kg containing 700–3000 mg leucine.

Who it helps, and who it doesn't

Largest gains in resistance-trained and younger adults, and in anyone whose baseline protein intake sits below ~1.6 g/kg/day. Untrained and older adults gained less in the meta-regression.

What to buy

What to look for
  • ✓Whey concentrate (~80% protein) or isolate (~90%) — isolate if lactose-sensitive; look for ≥2.5 g leucine per 25 g serving and third-party testing (Informed Sport / NSF)
  • ✓20–40 g per serving (0.25 g/kg body mass), enough to hit 1.4–2.0 g/kg/day total protein; benefit plateaus around 1.62 g/kg/day (95% CI 1.03–2.20)
  • ✓Third-party tested (USP, NSF, Informed Sport)
What to avoid
  • ✕Proprietary blends that hide the dose per ingredient
  • ✕Unstandardised extracts with no active-compound percentage
Safety notes
  • · Bloating, gas and cramping in lactose intolerance — switch to isolate or hydrolysate
  • · Acne flares are reported with whey in susceptible individuals
  • · No evidence of kidney harm in people with normal renal function, but high intakes are not appropriate in existing chronic kidney disease

As an Amazon Associate, Umbral earns from qualifying purchases. Product data is provided by Amazon and may change; ratings and prices shown are Amazon’s, not Umbral’s. Recommendations are based on the evidence grade and the form used in trials, never on commission.

Dymatize ISO100 Protein Powder, 100% Whey Isolate
Dymatize ISO100 Protein Powder, 100% Whey Isolate
4.6(20,824)
$38.22

Hydrolysed isolate, about 25 g protein and 5.5 g leucine per scoop, Informed Choice tested. The isolate matters only if lactose bothers you — otherwise concentrate does the same job cheaper.

Buy on Amazon
Amazon price on Sep 18, 2026.
Optimum Nutrition Gold Standard 100% Whey Protein
Optimum Nutrition Gold Standard 100% Whey Protein
4.6(100,257)
$49.16

A hundred thousand ratings, which makes it the most-reviewed protein on Amazon, and 24 g per scoop puts it inside the 20–40 g range that triggers the muscle-protein response.

Buy on Amazon
Amazon price on Sep 18, 2026.
NAKED Whey 2 lb, 100% Grass-Fed Whey Protein, Unflavored
NAKED Whey 2 lb, 100% Grass-Fed Whey Protein, Unflavored
4.3(10,900)
$62.99

One ingredient: whey. No sweetener, no gums, no flavour — the cleanest way to add protein to something you are already eating.

Buy on Amazon
Amazon price on Sep 18, 2026.
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What the studies measured

Every result, next to the line that means no effect

Each diamond is a study's best estimate. The thin line shows how sure the study was: the shorter the line, the more certain the result.

  • Fat-free mass gain
    kg · Morton et al., BJSM 2018
    +0.30
    +0.09 … +0.52
  • 1RM strength gain
    kg · Morton et al., BJSM 2018
    +2.49
    +0.64 … +4.33
0+2+4NO EFFECT
Different scale · effect size
  • Muscle function recovery at 72 h
    effect size · Davies et al., Nutrients 2018
    +0.70
    +0.20 … +1.30
0+0.5+1.0NO EFFECT
Different scale · effect size (null)
  • Creatine kinase / soreness
    effect size (null) · Davies et al., Nutrients 2018 — no benefit at any timepoint
    0.00
    [not given]
−0.10+0.1NO EFFECT

Each unit gets its own scale, so numbers are never mixed on one line. When a study gave no range, we leave it blank instead of inventing one.

Studies over time

3 studies over 1 years

2017 — 2018
20172018
Review combining many studiesControlled experimentEarly or observational studyHover a dot for details
Dose
20–40 g per serving (0.25 g/kg body mass), enough to hit 1.4–2.0 g/kg/day total protein; benefit plateaus around 1.62 g/kg/day (95% CI 1.03–2.20)
Timing
Anywhere in a 3–4 hourly distribution across the day; pre- or post-workout both work, the 'anabolic window' is at least 24 h wide. 30–40 g casein pre-sleep is the one genuinely time-specific protocol.
Where to buy

The studies

  1. 1.
    A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults
    British Journal of Sports Medicine · 2018 · meta-analysis · 49 experiments · n = 1,863

    FFM +0.30 kg (0.09–0.52), 1RM +2.49 kg (0.64–4.33); benefit plateaued at 1.62 g/kg/day (95% CI 1.03–2.20).

  2. 2.
    The Effect of Whey Protein Supplementation on the Temporal Recovery of Muscle Function Following Resistance Training: A Systematic Review and Meta-Analysis
    Nutrients · 2018 · meta-analysis · 13 experiments · n = 152

    Muscle function recovery ES 0.6 (0.1–1.0) at <24 h, 0.4 (0.1–0.8) at 24 h, 0.7 (0.2–1.3) at 72 h; median dose 25 g. No effect on CK or soreness.

  3. 3.
    International Society of Sports Nutrition Position Stand: protein and exercise
    Journal of the International Society of Sports Nutrition · 2017 · systematic review

    1.4–2.0 g/kg/day builds and maintains muscle; acute doses 0.25 g/kg or 20–40 g containing 700–3000 mg leucine; protein every 3–4 h.

Umbral is a wellness product, not a medical device. It does not diagnose, treat, cure or prevent any disease. Supplement information is educational; talk to a clinician before starting anything, especially if you are pregnant, under 18, managing a condition or taking medication.

These statements have not been evaluated by the Food and Drug Administration.