The Claim

In untrained young adults undergoing 12 weeks of resistance training, daily supplementation with either 26 grams of soy protein isolate or 19 grams of whey protein isolate (both providing 2 grams of leucine) results in no significant difference in the muscle thickness of the vastus lateralis.

Source: No Significant Differences in Muscle Growth and Strength Development When Consuming Soy and Whey Protein Supplements Matched for Leucine Following a 12 Week Resistance Training Program in Men and Women: A Randomized Trial

What the research says

Supports is higher

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

Supports
74score
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.

Quantitative
1 study reviewed
In plain English

For young people new to lifting weights, taking soy protein or whey protein daily seems to have the same effect on thigh muscle growth.

See the scientific wording

In untrained young adults, supplementing with 26 grams of soy protein isolate or 19 grams of whey protein isolate daily—both containing 2 grams of leucine—during 12 weeks of resistance training does not result in significant differences in muscle thickness of the vastus lateralis, with a non-significant trend toward increase (0.12 cm, p = 0.08) observed in both groups.

What the research says

1 study

  1. Study: No Significant Differences in Muscle Growth and Strength Development When Consuming Soy and Whey Protein Supplements Matched for Leucine Following a 12 Week Resistance Training Program in Men and Women: A Randomized Trial

    The study looked at the exact same protein supplements and exercise routine as described in the claim, and found that both groups had a small, not-quite-significant increase in leg muscle thickness, with no real difference between soy and whey.

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

Fit Body Science verdict — we translate health claims into clear verdicts backed by peer-reviewed research.

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