When you opt to take a supplement, stick to a dosage of 40 milligrams a day, which is the recommended adult intake. Too much zinc can cause complications, like inhibiting the absorption of other minerals like copper. Vitamin D is a steroid hormone that affects hundreds of genes in your body. Biotech Pro It is important for the healthy development of your sperm cell nucleus, quality of semen, and sperm count. Vitamin D can also raise testosterone levels, which can improve libido. One study showed that after being given vitamin D supplements, the testosterone levels of men increased in one year.