Vitamin D3 plays a crucial role in maintaining hormonal balance and supporting testosterone production. A randomized controlled trial demonstrated that vitamin D supplementation significantly increased total, bioactive, and free testosterone levels in healthy overweight men
undergoing a weight reduction program.
Pilz, S., Frisch, S., Koertke, H., Kuhn, J., Dreier, J., Obermayer-Pietsch, B., ... & Zittermann, A. (2011). Effect of vitamin D supplementation on testosterone levels in men. Hormone and Metabolic Research, 43(3), 223–225.