Discussion: Regular tanning (not excessive) may greatly help with erection, through the synthesis of the male hormone testosterone.

Most men are unaware of the immediate effect of tanning and vitamin D on erection. The hormone testosterone is a vitamin D derivative. (Taking vitamin D supplements does not have a similar outcome.) Controlled exposure to the sun is not the cause of skin cancer! Moderate sun exposure will significantly improve erection and also strengthen the immune system.

Link: Vitamins D3, B12, and Omega-3 are critical for proper immune function.
https://www.sf-healing.com/page/135 (Copy & Paste)