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Study analysis · Nutrients · 2023

Protein shakes after workouts are a multi-billion dollar industry—but this study shows they might be useless if you already eat enough protein.

If you already eat enough protein every day, adding a protein shake or chia drink after your workout doesn't build more muscle or strength than just lifting weights alone.

Reading level
Moderate certainty
Level 1b · Individual RCT

Overview

What the study found

The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.

In simple terms

This study is like a test where they gave three groups of people the same exercise program, but one group got a special drink with chia, one with whey protein, and one with just juice. They measured muscle and strength before and after. They found that all groups got stronger and gained muscle, but the drinks didn't make a difference. So this study shows that for these people, the extra protein drinks didn't help more than the exercise alone.

What’s the bottom line?

We tested if drinking a protein shake or chia drink after workouts helps build more muscle than just working out alone. In young men who already eat enough protein, it didn't help.

How strong is this study?

The study was done carefully - they randomly assigned people to groups, and the people didn't know which drink they got. But there were only 18 people total, which is a small number, so we can't be very sure that the results would be the same for everyone. Also, they only studied young men who already eat a lot of protein, so we can't say the same for other people.

Reporting

40 / 100

  • COI disclosure+40/40
  • Data availabilitydata not shared
  • Code availabilitycode not shared
Methodology

70 / 100

  • Randomization+20/20
  • Blinding+9/15
  • Control group+15/15
  • Sample size (n=18)+1.7/20
  • Follow-up+10/10
Publication

100 / 100

Statistical

46 / 100

  • P-values+15/15
  • Effect sizeno effect size reported
  • Confidence intervals+15/15
  • Pre-registrationnot pre-registered

Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.

Where it sits

RCT reviews

Max 100

Randomized Trials

Max 90

Reviews of Cohort Studies

Max 85

Cohort Studies

Max 72

Reviews of Case-Control Studies

Max 63

Case-Control Studies

Max 58

Cross-Sectional & Case Series

Max 50

Expert Opinion

Max 5
StrongerWeaker
Randomized Trials
Level 1b
64

64 / 100

Probability of being correct

Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.

This design can establish causation. As an RCT, this study can establish causal relationships, but the null result is limited by the small sample size (n=18) and the specific population (healthy untrained young men with high habitual protein intake). The absence of a significant effect does not prove that no effect exists in other populations or under different conditions.

No Conflicts

No conflicts of interest identified

Not Disclosed

No conflicts of interest were declared in the provided text. The study appears to be independently conducted.

Undisclosed — Suspicious

The study uses commercial products (Benexia chia powder, Syntrax whey protein, Daily juice) but no funding or COI is disclosed. The full paper may contain a COI statement not included in the provided excerpt.

Key takeaways

  1. 01

    All groups gained 2-3% more muscle and got stronger, but the protein drinks didn't add extra gains.

  2. 02

    For people with high protein diets, extra supplements may not be needed.

Surprising findings

  • Neither whey protein nor chia flour improved muscle or strength gains compared to placebo in young men with high protein intake.Most fitness culture emphasizes post-workout protein as crucial, and previous studies often show benefits, but this contradicts that when total protein is high, extra doesn't help.
  • The placebo group gained 3.0% fat-free mass, which was not significantly different from the whey group's 2.3% and chia group's 3.6%.Even without any protein supplement, beginners can gain muscle from training alone, and adding protein didn't add extra.
  • Participants couldn't guess which supplement they received – all were blinded successfully.The placebo was a sugar-free orange juice, but participants didn't know if they got protein or not, so the psychological effect of knowing you're taking something might not matter.

Practical takeaways

If you already eat 1.2-1.5 g/kg of protein daily, you probably don't need to rush a protein shake after your workout – just hit your daily protein target.

This study only looked at young untrained men with high protein intake; if you're older, vegan, or eat less protein, you might still benefit from supplements.

medium confidence

Focus on total daily protein intake rather than obsessing over post-workout timing or source.

The study was short (8 weeks) and small (n=6 per group), so longer-term effects might differ.

medium confidence

If you're a beginner, just lifting weights consistently will build muscle even without supplements – don't think you need protein shakes to see gains.

All groups gained muscle, so training itself is effective.

high confidence

Why this study matters

The 'muscle full' effect: when extra protein does nothing

In this 8-week study, 18 untrained young men who already consumed 1.3–1.5 g/kg/day of protein gained 2.3–3.6% fat-free mass from resistance training alone, but adding 23g whey protein or 20g chia protein after each workout gave no extra benefit. The 'muscle full' hypothesis suggests that once your body has enough amino acids, extra protein doesn't trigger more muscle growth.

Most gym-goers believe protein timing is critical, but this shows that total daily protein intake matters more than the supplement you chug after a workout.

Chia vs. whey: plant protein doesn't lag behind animal protein

Chia flour (20g protein, 3g omega-3) performed just as well as whey protein (23g) and placebo in terms of muscle and strength gains. All groups improved similarly, with no significant differences between them.

Plant-based protein sources are often considered inferior, but this study suggests that when total protein is adequate, the source doesn't matter for muscle gains.

The placebo group gained just as much muscle as the protein groups

The placebo group (no protein supplement) gained 3.0% fat-free mass, while whey gained 2.3% and chia gained 3.6% – no statistical difference. Strength gains were also similar across all groups.

This challenges the idea that post-workout protein is essential for muscle growth, especially for beginners.

The study's limitations: small sample, short duration, only young men

Only 18 young men (6 per group) were studied for 8 weeks, and all were untrained and had high habitual protein intake. This limits generalizability to other populations like women, older adults, or those with lower protein intake.

It's important to know that this 'no effect' might not apply to everyone – vegans, vegetarians, or elderly might still benefit from supplements.

Want the whole report?

Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.

Standing

Who’s using this study?

The videos and claims on this site that lean on this study, and the researchers who wrote it.

1 video from Siim Land cite this study, drawing 1 claim from it.

Siim Land
This Is Why Your Workouts Stopped Working
Citing claim
All 1 video reference this study through extracted claims.