The Claim

In vitamin D-deficient young males, resistance training alone—without protein or vitamin D supplementation—leads to improvements in lower-body strength, such as leg press one-repetition maximum, but does not significantly increase muscle mass or alter key muscle-related hormones.

Source: Muscle-Related Effect of Whey Protein and Vitamin D3 Supplementation Provided before or after Bedtime in Males Undergoing Resistance Training

What the research says

Challenges is higher

Challenge is ahead, but a single strong supporting study can change this.

Supports
0score
Challenges
54score

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

If young guys who don’t have enough vitamin D do strength training without taking extra protein or vitamin D, they can get stronger legs—but their muscles won’t grow much, and their muscle hormones won’t change.

See the scientific wording

Resistance training alone without protein or vitamin D supplementation leads to improvements in lower-body strength (e.g., leg press 1RM) but does not significantly increase muscle mass or alter key muscle-related hormones in vitamin D-deficient young males.

What the research says

1 study

  1. Study: Muscle-Related Effect of Whey Protein and Vitamin D3 Supplementation Provided before or after Bedtime in Males Undergoing Resistance Training

    The study looked at young men doing strength training without protein or vitamin D, but it didn’t specifically study those who were vitamin D deficient, so it doesn’t fully match the claim.

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.