The Claim

In healthy older adults aged 61.5 ± 7.4 years undergoing 12 weeks of resistance training three times per week, increased soy protein intake (1.42 ± 0.61 g/kg/d) results in significantly smaller gains in muscle strength compared to increased dairy protein intake or usual protein intake, with a statistically significant treatment effect (P = 0.002).

Source: Muscle strength gains during resistance exercise training are attenuated with soy compared with dairy or usual protein intake in older adults: A randomized controlled trial.

What the research says

Supports is higher

Support is ahead, but a single strong opposing study can change this.

Supports
51score
Challenges
0score

These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.

Cause and effect
1 study reviewed
In plain English

In older adults doing resistance training for 12 weeks, consuming soy protein leads to smaller increases in muscle strength than consuming dairy protein or their usual protein intake.

See the scientific wording

In healthy older adults aged 61.5 ± 7.4 years undergoing 12 weeks of resistance training three times per week, increased soy protein intake (1.42 ± 0.61 g/kg/d) resulted in significantly smaller gains in muscle strength (63.0 ± 23.8%) compared to increased dairy protein intake (92.1 ± 40.8%) or usual protein intake (92.3 ± 35.4%), with a statistically significant treatment effect (P = 0.002), suggesting protein source may influence strength adaptation during resistance training in this population.

Why this might work

Soy protein provides less leucine than dairy protein, so after eating soy, muscles receive a weaker signal to start building new muscle proteins. This means the muscles don't grow as strong during training, even when the person lifts weights regularly.

Supported mechanismbased on 1 study

What the research says

1 study

  1. Study: Muscle strength gains during resistance exercise training are attenuated with soy compared with dairy or usual protein intake in older adults: A randomized controlled trial.

    In older adults doing strength training, those who ate more soy protein got weaker strength gains than those who ate more dairy protein or ate their normal amount. The study found this difference was real and not due to chance.

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies

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Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.