Observational studies have found that men with erectile dysfunction (ED) tend to have lower levels of plasma folate compared to men without ED, and folate level seems to negatively correlate with the severity of ED.[1][2] While research is still preliminary, folic acid supplementation may improve symptoms of ED for some men, including when used in addition to the ED medication tadalafil.[2]
As it relates to male infertility, limited research suggests that folic acid supplementation may increase sperm motility in infertile men, but does not seem to affect sperm concentration or morphology. It’s currently unknown if this benefit leads to increased rates of pregnancy.[3] Interestingly, genetic polymorphisms in methionine synthase (MTR) — an enzyme involved in folate metabolism — have been strongly associated with male infertility, most notably in Asian populations.[4] It’s been suggested that folic acid may improve male fertility through antioxidant mechanisms or by promoting DNA methylation during sperm production.[3]