Vitamin D, a hormone produced by the body through exposure to sunshine or obtained from foods such as fatty fish and egg yolk, helps the body control calcium and phosphate levels. Previous studies have linked vitamin D levels with a range of health problems including cardiovascular disease and cancer.
Up to 80% of the population in Europe are affected by low vitamin D levels. As this is particularly common amongst people who lead unhealthy, sedentary lifestyles, low vitamin D levels have been associated with obesity; at the same time as obesity is rising, vitamin D levels are falling. In addition, female fertility and semen quality have deteriorated in the recent years due to largely unknown causes. Infertility rates amongst couples who want to have children are at 10-15%, and up to 10% of women of reproductive age suffer from polycystic ovary syndrome (PCOS), a condition which may hinder fertility.
Dr Elisabeth Lerchbaum, from the Medical University of Graz, has led much research on the effects of vitamin D supplementation in different aspects of male and female fertility. Research from her group and others suggests vitamin D affects many aspects of fertility in both genders, including influencing production and maturation of sperm cells in men, egg cell and uterine lining maturation in women, and sex hormone production in both sexes. Vitamin D levels have been associated with in-vitro fertilisation (IVF) outcome, some features of PCOS and endometriosis in women. In men, levels of vitamin D have been linked to semen quality and male hormone levels in both fertile and infertile men.
Further studies have shown beneficial effects of vitamin D supplementation in some stages of egg cell maturation and menstrual cycle regulation in women suffering from PCOS. Other findings suggest benefits of vitamin D supplementation in metabolic conditions -such as type-2 diabetes, obesity and metabolic syndrome- in PCOS women.
There is evidence that vitamin D supplementation can improve semen quality, fertility outcomes and testosterone concentrations. Recent studies suggest that vitamin D supplementation could be beneficial for couples undergoing IVF.
Although accumulating evidence from animal and human studies suggests that vitamin D deficiency may have a negative effect in fertility, more research is needed to determine whether it causes it.
“High quality randomised controlled trials are needed to evaluate how vitamin D supplementation affects fertility and sex hormone production in men and women. There is also an ongoing debate about what the optimal dose of vitamin D levels and supplementation should be.” says Dr Lechbaum. “Looking at the metabolism of vitamin D could open up new treatment methods. Vitamin D supplementation might be a safe and affordable treatment option in PCOS or might support couples who want to have children.”
A second large-scale randomised controlled trial in women with and without hormonal imbalances will be finished this year. Depending on the results, the research group will focus on studying optimal vitamin D levels and supplementation dose.