The Claim

In young males with vitamin D deficiency who are undergoing resistance training, daily supplementation with 25 grams of whey protein and 4000 IU of vitamin D3 for 6 weeks results in significantly greater increases in total lean tissue mass, leg lean tissue mass, and appendicular lean tissue mass compared to resistance training alone with placebo, with reported gains of 1.5–1.8 kg in total lean mass and 0.6 kg in leg lean mass.

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

Supports is higher

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

Supports
54score
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

If young guys who don't get enough vitamin D lift weights and take a daily combo of whey protein and a high dose of vitamin D, they'll gain more muscle — especially in their legs — than those who just lift weights without the supplements.

See the scientific wording

In vitamin D-deficient young males undergoing resistance training, combined supplementation with 25 grams of whey protein and 4000 IU of vitamin D3 daily for 6 weeks causes significantly greater increases in total lean tissue mass, leg lean tissue mass, and appendicular lean tissue mass compared to resistance training alone with placebo, with gains of 1.5–1.8 kg in total lean mass and 0.6 kg in leg lean mass.

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 shows that young men who took whey protein and vitamin D3 while doing strength training gained more muscle than those who didn’t, which supports 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.