May 23, 2017

expert reaction to conference talk about vitamin D supplements and fertility

In a conference poster presented at the European Congress of Endocrinology scientists investigate whether vitamin D supplementation could improve both male and female fertility.

Dr Martin Bloomberg, Member of the Society for Endocrinology, & Senior Researcher at the Department of Growth and Reproduction, Rigshospitalet, Denmark, said:

“Currently there is not enough evidence to support a recommendation that couples trying to have children should take vitamin D supplements, but I think it is fair to claim that it can be recommended to avoid vitamin D deficiency (serum 25OHD < 25 nmol/l = 10 ng/ml) in men and women part of a couple trying to conceive. There is no data indicating that sufficient vitamin D status is harmful for parents or foetus, but there is accumulating evidence for a poor outcome in mothers with vitamin D deficiency both regarding fertility, abortions and child health.

“We have supportive data from animal experiments and small RCTs in men and women part of an infertile couple where vitamin D supplementation seems to improve fertility potential. At this moment data are supportive but there is not enough evidence to suggest treatment with high dose vitamin D.

“The main problem is that there exists no large well designed randomised control trial (RCT) of the effects of vitamin D on fertility in men or woman with live birth rate, pregnancies or semen quality as the primary endpoint. Most information is based on animal models, cross-sectional human studies or small intervention studies with no placebo control. The clinical trials in PCOS women are small and results are in conflict, although there is some evidence for a beneficial effect on the sex steroid profile.

“Most human studies investigating the link between vitamin D status and fertility are limited by their cross-sectional study design that does not allow us to define any causal relevance, which implies that vitamin D status simply may be a marker for the health status of the person. However, the most compelling evidence comes from a similar phenotype in both animals and humans with vitamin D deficiency, which both results in impaired female and male fertility. In rodents, this impairment is fully reversible following supplementation with vitamin D and calcium, but more studies are required to determine whether this holds true in humans.”

Dr Yakoub Khalaf, Director of the Assisted Conception Unit, Guy’s and St. Thomas’ Hospital Foundation Trust, said:

The association between vitamin D and improving fertility in women and men has received a lot of attention recently. However, good evidence of effectiveness is needed before recommending vitamin D supplementation routinely to infertile couples. I hope that the new data promised in this presentation would provide such good evidence.

Prof. Sheena Lewis, Emeritus Professor of Reproductive Medicine, Queen’s University Belfast, said

“Antioxidants are increasingly being recommended for health improvement but this can be dangerous. A number of studies show that too many antioxidants can harm rather than help our health. Men actually need a low level of free radicals for their sperm to function normally and excess antioxidants can damage sperm irreversibly. Couples should not take antioxidants unless they have been tested and found to have a deficiency.

* ‘Effect of vitamin D supplementation on endocrine and metabolic parameters in hypogonadal men’ by Lerchbaum will be presented at the European Congress of Endocrinology on Tuesday 23 May 2017

Declared interests

Dr Martin Bloomberg: Martin Blomberg Jensen is PI on multiple clinical trials investigating vitamin D in reproduction.

Prof. Sheena Lewis: Sheena is CEO of Lewis Fertility Testing Ltd, a university spin-out company marketing a test for male infertility: www.spermcomet.com

None others received.