The Journal of urology2026n = 2,205 men
Cross SectionalHuman
This study looked at whether time spent outdoors is linked to testosterone in men. It analyzed 2,205 men in the US National Health and Nutrition Examination Survey, tracking daily outdoor…
Nutrients2026n = 75 enrolled, 70 completed
RCTHuman
This study looked at whether vitamin D changes how well metformin (a common diabetes drug that lowers blood sugar) can bring down prolactin (a pituitary hormone that suppresses testosterone when…
European urology focus2026n = 2209
Cross SectionalHuman
This study set out to see whether exposure to bright light is linked to testosterone in men, an area far less studied than diet and exercise. It analyzed data from…
Nutrients2026n = 34
RCTHuman
This study looked at how high-intensity exercise and vitamin D3 supplements affect vitamin D levels differently in trained athletes versus untrained men. It compared 22 mixed martial arts athletes and…
Clinical nutrition research2026n = 4,819
Cross SectionalHuman
This study looked at whether vitamin D levels are linked to metabolic health, measured by the TyG index (a score from fasting blood sugar and triglycerides that flags insulin resistance,…
Nutrients2026n = 21 comparison-level records from 18 reports
Meta AnalysisHuman
This systematic review and meta-analysis set out to see whether vitamin D supplements raise testosterone or related markers in men. It pooled randomized trials measuring total testosterone, SHBG (sex hormone-binding…