Research published in the Asian Journal of Andrology aims to explore the association between serum vitamin D levels and semen and hormonal parameters.
Previous animal and human studies have demonstrated the importance of adequate vitamin D status for male and female reproductive health. However, research supporting a specific vitamin D status range for optimal reproductive health has been elusive.
Dr Ahman Hammoud and colleagues recruited 170 healthy men to participate in the study. The population consisted of men 18-67 years, from all ethnic backgrounds.
The participants’ vitamin D status was assessed, as well as hormone and sperm parameters, including sperm concentration, motility, morphology (percent normal sperm head), total sperm count per ejaculate, and total motile sperm count per ejaculate.
The researchers found surprising results. The percent normal sperm head, percent progressive motile sperm, sperm concentration, and total progressive motile sperm count were lower in men with 25(OH)D status ≥50 ng/mL. Men with 25(OH)D <20 ng/mL exhibited lower total sperm count values and lower total progressive motile sperm. The authors found no statistical differences between the mean hormonal values in the different 25(OH)D categories.
The authors note the results suggest a possible inverted ‘U shaped’ relation of vitamin D to sperm parameters.
Dr A Wayne Meikle, MD, co-author of the study states, “We did not expect that high level of vitamin D would adversely affect semen parameters.” In regards to future research on the subject, “There continues to be interest in male reproductive endocrinology and vitamin D. This study might shift further research to reproductive function.”
The authors recognize limitations to the study. Vitamin D deficiency was lower in the study population (12.4%) than for a healthy population. Also, participants provided one semen sample, which doesn’t account for individual variation in semen quality. The researchers conclude,
“The unexpected finding in this study calls for more studies that included larger numbers of participant with more men in either the high or low vitamin D categories and studies of the effect of vitamin D supplementation on semen analysis to demonstrate causality.”