The mineral zinc plays a vital role in helping to support healthy production of testosterone, which has a supportive effect on spermatozoa. Vitamin D levels and Zinc status should be checked, as these are associated with fertility in men. A specific nutrient known as D-aspartic acid; a natural amino acid shown to help support testosterone levels. Research suggests that it works mainly by supporting levels of follicle-stimulating hormone and luteinizing hormone, the latter of which stimulates Leydig cells in the testes, to produce sufficient testosterone.