Protein & Muscle: Does Supplementation Help?

meta-analysis PMID: 28698222

Quick Summary: Research shows that taking extra protein, along with weight training, can help you build more muscle and get stronger. However, there's a limit – more protein isn't always better!

Does Protein Supplementation Build Muscle?

Yes! This research looked at many studies and found that people who took protein supplements while doing resistance training (like lifting weights) gained more muscle mass and strength compared to those who didn't.

What The Research Found

Stronger Muscles: People got significantly stronger, able to lift about 5.5 pounds more in a single lift.

Bigger Muscles: They also gained more "fat-free mass" (muscle), about 0.66 pounds.

Muscle Fiber Growth: The size of their muscle fibers increased.

Too Much Protein? The study found that taking more than about 1.6 grams of protein per kilogram of body weight per day didn't lead to even more muscle growth.

Study Details

Who was studied: Healthy adults who were doing resistance training (weightlifting).

How long: The studies lasted at least 6 weeks.

What they took: Protein supplements, along with their regular diet and weight training.

What This Means For You

If you lift weights: Adding protein supplements to your diet can help you build muscle and get stronger.

Don't overdo it: You probably don't need to take massive amounts of protein. Aim for around 1.6 grams of protein per kilogram of your body weight per day.

Consider your age and experience: Younger people and those new to training might see bigger benefits from protein.

Study Limitations

Not everyone is the same: The study looked at a wide range of people, so results might vary.

More research needed: The study didn't look at specific types of protein or how often to take it.

Focus on total protein: The study focused on total protein intake, not specific amino acids like leucine.

Short-term study: The studies were relatively short, so we don't know the long-term effects.

Key Findings

The meta-analysis found that dietary protein supplementation significantly improved muscle strength (2.49 kg increase in 1-repetition maximum), fat-free mass (FFM) gains (0.30 kg), and muscle fiber cross-sectional area (CSA; 310 µm²) in healthy adults undergoing resistance training (RET). However, the benefits plateaued at protein intakes above ~1.6 g/kg/day. Efficacy was reduced in older individuals and enhanced in experienced trainees.

Study Design

This 2018 meta-analysis included 49 randomized controlled trials (RCTs) with 1,863 participants. Studies required RET interventions lasting ≥6 weeks and protein supplementation. Researchers used random-effects models and meta-regression with four covariates (age, training experience, protein dose, baseline protein intake). Two-phase breakpoint analysis assessed the dose-response relationship between protein intake and FFM changes.

Dosage & Administration

Total protein intake (from supplements and diet) was analyzed as a covariate. The study identified ~1.6 g/kg/day as the threshold where additional protein no longer enhanced FFM gains. Specific administration methods (e.g., timing, type of protein) were not detailed in the summary, but supplements were provided alongside RET programs.

Results & Efficacy

Protein supplementation significantly increased:
- Muscle strength: 2.49 kg (95% CI: 0.64–4.33; p<0.05) improvement in 1RM.
- Fat-free mass: 0.30 kg (95% CI: 0.09–0.52; p<0.05) increase.
- Muscle fiber CSA: 310 µm² (no CI or p-value reported).
Meta-regression showed diminishing returns above 1.6 g/kg/day. Age negatively correlated with efficacy, while training experience positively correlated with FFM gains.

Limitations

Heterogeneity: Variability in study populations (e.g., age ranges, training status) may affect generalizability.
Publication bias: Smaller studies with null results might be underrepresented.
Covariate constraints: Analysis focused on total protein intake, not specific amino acids (e.g., leucine) or protein types.
Short duration: RET interventions ≥6 weeks may not capture long-term effects beyond study periods.
Assumptions in breakpoint analysis: The ~1.6 g/kg/day threshold relies on statistical modeling rather than direct experimental comparison.

Clinical Relevance

For healthy adults engaging in RET, protein supplementation enhances muscle growth and strength gains. However, exceeding 1.6 g/kg/day offers no additional benefit for FFM. Older individuals may require tailored strategies, while experienced trainees see amplified results. Practically, this supports protein supplementation as a safe and effective adjunct to RET, with dose optimization critical for cost and compliance.

Note: The study focused on total protein intake rather than isolated leucine, though leucine’s role in muscle protein synthesis may partially underpin these results. Demographics: Participants were healthy adults (no specific age range provided in summary).

Source: PubMed (PMID 28698222)