The Claim

Leucine supplementation, at doses up to 5g/day over 8–12 weeks, does not significantly increase muscle strength (e.g., 1RM) in healthy, trained young adults undergoing resistance training when compared to a placebo.

Source: Effects of leucine intake on muscle growth, strength, and recovery in young active adults: a systematic review of randomized controlled trials

What the research says

Supports is higher

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

Supports
20score
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

Taking leucine supplements won’t make you stronger in the gym if you’re already a healthy, trained young adult lifting weights—even if you take up to 5 grams a day for a couple of months.

See the scientific wording

Leucine supplementation does not significantly increase muscle strength (e.g., 1RM) in healthy, trained young adults undergoing resistance training when compared to placebo, even with doses up to 5g/day over 8–12 weeks.

What the research says

1 study

  1. Study: Effects of leucine intake on muscle growth, strength, and recovery in young active adults: a systematic review of randomized controlled trials

    This study looked at whether taking leucine pills helps strong, active young people get stronger, and found it doesn’t — just like the claim says.

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.