Abnormal vitamin D levels associated with ‘altered semen parameters’
MedWire News: Men with abnormally high or abnormally low levels of vitamin D (25OHD) have low sperm motility and abnormal sperm morphology, show study results from nearly 300 US men.
The results were presented at the 27th annual conference of the European Society for Human Reproduction and Embryology in Stockholm, Sweden.
"The incidence and prevalence of vitamin D deficiency is reaching an epidemic level," said presenting author Ahmad Hammoud (University of Utah, Salt Lake City, USA).
"Some estimate the incidence of vitamin D deficiency is between 27% and 100% depending on the population studied," he added.
The relationship between 25OHD and health disorders is likely to be "U-shaped" according to recent guidelines published by the US Institute of Medicine, with any levels outside the norm (20-50 ng/ml) increasing the incidence of poor health outcomes.
To investigate a possible association between 25OHD and male reproductive health, Hammoud and colleagues carried out a study involving 270 healthy men from the general community.
Participants completed a detailed questionnaire regarding their nutritional and supplementary vitamin intake, as well as their alcohol and tobacco consumption, and the men's semen parameters (morphology) and hormone levels were also examined.
A total of 75.3% of men had 25OHD levels within the normal range, which was divided into two: 20-30 ng/ml (28.8%) and 30-50 ng/ml (46.5%), respectively.
After adjusting their analysis for potential confounders, men with abnormal levels of the vitamin had significantly lower sperm motility than those with normal 25OHD levels.
Specifically, men with less than 20 ng/ml 25OHD or 50 ng/ml or more, had 71.2 and 77.6 million motile sperm, compared with 182.2 and 126.3 million in men with respective 25OHD levels of 20-30 ng/ml and 30-50 ng/ml.
Men with abnormal 25OHD levels also had a lower overall sperm concentration, a lower percentage of motile sperm, and a lower percentage of sperm with normal heads.
However, no association was observed between 25OHD levels and reproductive hormone levels including testosterone, lutenizing hormone, and sex hormone-binding globulin.
This suggests that "the deleterious effect on sperm parameters may not be hormonally mediated," said the researchers.
The study findings also highlight a link between body mass index and 25OHD, with mean vitamin levels of 36.4 ng/ml in normal weight men, compared with 22.2 ng/ml in obese men.
"Whether vitamin D is a causative factor in these changes in sperm parameters, as opposed to being a surrogate marker for poor health, remains to be elucidated," concluded the research team.
MedWire (www.medwire-news.md) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011
By Sarah Guy