One of the main causes of male infertility is sperm DNA damage. Studies show that sperm DNA damage can be efficiently treated with oral antioxidants such as vitamin E and C. (See below in Andrology Journal for Reference) If a man's sperm has been tested and shown to have poor quality sperm he should consider supplements such as A, C, E, Selenium, Zinc, Folic acid L-Carnitine and CO Q10 (in doses that are higher than what you find in a multi-vitamin mineral). If there are no problems with the man's sperm counts/motility/DNA then simply a high quality multi-vitamin mineral should be considered. More important than any supplement, is that both partners should consider eating very healthy and exercising for a minimum of 3 months prior to conception. They should also aim to achieve a healthy Body Mass Index (under 25) to improve chances of conception.
The recommended daily vitamin D dose for the average man and woman is 1,000iu but it's best to have your serum (blood) 25-OH-Vitamin D levels checked in order to know what dose is best for you.
Remember to seek advice from a primary healthcare provider (medical doctor or naturopathic doctor) before taking advice over this medium.
target="_blank">Anitoxidants C and E improve sperm quality
target="_blank">CoQ10 improves sperm quality
target="_blank">L-Carinitine improves sperm quality