Soy Protein for Soccer Players: Does It Boost Recovery?

randomized-controlled-trial PMID: 33726784

Quick Summary: A study found that soy protein can help male soccer players maintain their high-intensity running performance during tough training. Both soy and whey protein helped, but soy might also speed up recovery from muscle stress.

Does Soy Protein Help Athletes Recover?

This research looked at how soy protein affects soccer players after intense training. The goal was to see if it could help them recover faster and perform better. The study compared soy protein to whey protein (a common supplement) and a placebo (a sugar powder).

What The Research Found

Better Performance: Both soy and whey protein helped players maintain their high-speed running during training.

Faster Recovery (Possibly): Soy protein seemed to help players recover from muscle stress a bit faster than whey or the placebo.

Muscle Soreness: Neither soy nor whey protein significantly reduced muscle soreness or damage after training.

Study Details

Who was studied: 10 well-trained male soccer players.

How long: The study lasted for a few days, with a week of preparation beforehand.

What they took: Players took either soy protein, whey protein, or a placebo (sugar powder). They aimed for 1.5 grams of protein per kilogram of body weight each day.

What This Means For You

For Soccer Players: If you're a male soccer player, soy protein could help you maintain your speed and intensity during tough training sessions. It might also help your muscles recover a bit faster.

Plant-Based Option: Soy protein is a good option if you prefer a plant-based protein supplement.

Not a Magic Bullet: Protein supplements alone might not completely eliminate muscle soreness. Make sure you're also getting enough rest and other recovery methods.

Study Limitations

Small Study: The study only included 10 players, so the results might not apply to everyone.

Short Time Frame: The study only looked at recovery over a few days.

Only Men: The study only included men, so the results might be different for women.

Protein Intake: The placebo group had a lower protein intake, which could have affected the results.

Key Findings

Soy protein supplementation (1.5 g/kg/day) improved maintenance of high-intensity running performance during successive speed-endurance training sessions in competitive male soccer players compared to placebo. Both whey and soy protein mitigated declines in field activity, but soy uniquely accelerated recovery of protein carbonyls (a marker of oxidative stress) at 48 hours post-exercise (P ≤ 0.05). Neither protein type reduced muscle damage markers (e.g., creatine kinase, delayed-onset muscle soreness) or preserved redox status (glutathione, total antioxidant capacity) more effectively than placebo.

Study Design

This was a randomized, double-blind, crossover controlled trial involving 10 well-trained male soccer players (age: ~23 years, VO₂max: ~58 mL/kg/min). Participants completed three trials: whey protein (WP), soy protein (SP), or isoenergetic placebo (PL, maltodextrin). Each trial included a 7-day pre-loading phase to standardize protein intake, followed by two speed-endurance training sessions (1 day apart) over 3 days. Field activity (GPS), heart rate, performance metrics (sprint, jump, strength tests), and blood biomarkers were assessed at baseline, post-preloading, and recovery intervals (24–72 hours).

Dosage & Administration

Participants received supplements to achieve 1.5 g/kg/day of protein in WP and SP trials (individualized based on body weight), while PL maintained 0.8–1 g/kg/day. The study did not specify exact timing of supplementation relative to training but ensured intake was distributed across days. Supplements were administered in powder form, mixed with water, and matched for energy content.

Results & Efficacy

Field Performance: High-intensity running distance decreased in all trials (P ≤ 0.05), but WP and SP reduced performance deterioration compared to PL.
Speed: 10-m sprint time worsened at 24 hours post-training only in PL (P ≤ 0.05).
Muscle Damage: Creatine kinase (CK) increased post-training (~350 U/L peak) and DOMS peaked at 48 hours (~60 mm on VAS scale) equally across trials (P ≤ 0.05).
Redox Status: Total antioxidant capacity and protein carbonyls increased post-training (P ≤ 0.05), but SP showed 20% lower protein carbonyls at 48 hours vs. WP/PL (P = 0.03). Glutathione decreased similarly in all groups (P ≤ 0.05).
Strength & Power: Isokinetic knee strength, countermovement jump, and repeated sprint ability declined post-training (P ≤ 0.05), with no differences between supplements.

Limitations

Small sample size (n=10) limits generalizability.
Short-term design (72-hour recovery) does not assess long-term adaptations.
Dietary intake was not fully controlled, potentially confounding results.
No female participants; findings may not apply to women.
Placebo group had lower baseline protein intake (0.8–1 g/kg/day vs. 1.5 g/kg/day), which could influence outcomes.
Lack of mechanistic insights (e.g., myofibrillar protein synthesis rates).

Clinical Relevance

For competitive male soccer players, increasing daily protein intake to 1.5 g/kg via soy or whey helps maintain high-speed running performance during consecutive speed-endurance sessions. Soy protein may offer additional benefits for oxidative stress recovery (via reduced protein carbonyls at 48 hours), though both proteins were equally effective at preserving most performance metrics. However, neither supplement attenuated muscle damage markers, suggesting protein supplementation alone may not fully address recovery needs in this population. Practical applications include using soy as a plant-based alternative to whey for acute recovery support, particularly in scenarios requiring rapid return to high-intensity activity.

Source: PubMed | Trial Registration: NCT03753321