Surprising
A four-week trial found 6000 IU/day of vitamin D3 boosted blood levels in MMA athletes — but 3500 IU/day did the same for untrained men, while failing in the athletes.
This pilot study suggests that training status, not just baseline deficiency, may determine how much vitamin D3 you need to raise your levels — a useful reminder that one-size-fits-all dosing advice may miss the mark, though the small sample and short duration mean the pattern is far from settled.
In a single-blind trial, mixed martial arts athletes and untrained men each took vitamin D3 for four weeks. The athletes needed 6000 IU/day to significantly increase their blood vitamin D levels, while 3500 IU/day was enough for the untrained group — but that same lower dose had no effect on the athletes. The study also noted improvements in power and work capacity among the athletes, but those results were not statistically tested.
Where this fits in the evidence
This is among the first studies we've indexed on Vitamin D3 for Increased Vitamin D Level — treat it as an early signal until more research accumulates.
The study
- Randomized Controlled Trial (RCT)
- 2026-03-26
- Nutrients
- PubMed: 41978112
- DOI: 10.3390/nu18071061
- Full study breakdown →
This is a plain-language summary of a research finding, not medical advice. Pillser surfaces research signals to help you decide what's worth investigating — always consult a qualified professional before changing what you take.