The study, conducted in 300 normal men, showed a positive correlation between the percentage of motile sperm and serum vitamin D levels.
Dr Martin Blomberg Jensen, Department of Growth and Reproduction, Copenhagen University, told NutraIngredients: “In animals it is known that vitamin D deficiency results in low sperm count and low sperm motility and if you knock out the vitamin D receptor in mice it results in low sperm motility and low sperm number.
“We have recently shown that the vitamin D receptor and all metabolizing enzymes are expressed in human testis and spermatozoa. Now we show that vitamin D is important for human spermatozoa by showing that activated VD (vitamin D) induces sperm motility in the lab….”
Men with high vitamin D levels of up to 75 nmol/l had a significantly higher sperm motility compared with vitamin D deficient men with up to <25 nmol/l men.
But the results are not sufficient to justify changing treatments, said Jensen. “This finding is not sufficient in determining whether vitamin D supplements may improve sperm quality in normal or infertile males. This study is one in a line of studies indicating that vitamin D is necessary for male reproduction.”
More research is needed to identify relevant factors and conduct placebo-controlled trials to clarify whether vitamin D supplements are beneficial for infertile men, said the researchers.
There is no known medical treatment proved to improve semen quality in well-designed randomised trials. Several papers have shown numerous positive associations between various treatments such as antioxidants, zinc, various vitamins and semen quality.
Professor Anders Juul, Copenhagen University Hospital’s Department of Growth and Reproduction, said: "Low semen quality may have numerous causes, but it often has a fetal origin similar to some male genital malformations and testicular cancer. However, this study indicates that factors in adult life may also play a role for semen quality.”
The semen quality of Danish men is at a low level and contributing to a high incidence of fertility problems among Danish couples, he continued.
Jensen added: “Semen quality has, in some countries, reached a level where an increasing fraction of young men are at risk of fertility problems.
“Impaired semen quality, testicular cancer, cryptorchidism and hypospadias are risk factors for each other, and the testicular dysgenesis syndrome has been put forward to explain the observations.”
Denmark and Norway have the highest incidence of testis cancer in the world and impaired semen quality. In Denmark, 10 per cent of all children are born after assisted reproduction.
Source: Oxford Journal of Human Reproduction.
Title: Vitamin D is positively associated with sperm motility and increases intracellular calcium in human spermatozoa.