Vitamin D plays a role in human fertility. Deficiency of vitamin D can cause infertility among women and men.
Austrian physicians Barbara Obermayer-Pietsch and Elisabeth Lerchbaum found that low levels of vitamin D often lead to too much testosterone, which therefore could increase the risk of infertility among women. Also, when men are given extra vitamin D they produce more testosterone subsequently affecting the semen quality.
Researchers said, "It may not be that controlling vitamin D is the ultimate answer to fertility problems but it could be a very cheap and simple solution at least in some cases."