Sun, sex and babies: Could vitamin D boost fertility?

Exposure to increased levels of vitamin D could boost your fertility, a recent study suggests. The findings may also explain why conception rates fall in the winter and peak in the summer in Northern European countries.

According to researchers from the Medical University of Graz in Austria, it has been known for some time that the vitamin D receptor is found in the reproductive organs of women and men. However very little was known about the role the nutrient played in reproductive health.

The study, published in the European Journal of Endocrinology, reviewed previously conducted research evaluating the relationship between vitamin D and fertility in women and men, as well as in animals.

The investigations showed that male mice bred to lack vitamin D receptors had lower sperm counts, while the females had abnormal ovary function.

Studies in humans present evidence that increased levels of vitamin D balance sex hormones in women and regulate the menstrual cycle, increasing levels of progesterone by 13 percent and oestrogen by 21 percent. In men, the nutrient was found to increase sperm count and improve sperm quality and testosterone levels.

Furthermore, in two of the studies reviewed it was found that conception may be more likely in the summer months. In a study of 2,300 men, researchers found that levels of testosterone and vitamin D peaked in the summer months and were at their lowest in March, after the winter. Women were also found to ovulate less in the winter months.

The studies led the Austrian team to conclude that, 'in addition to… the classic regulators of human reproduction, vitamin D also modulates reproductive processes in women and men'.

Does this mean that a sunshine holiday is in order? Lead author Dr Elisabeth Lerchbaum warned that although vitamin D could help to improve fertility, overexposure could lead to skin cancer.

She said: 'People could either spend more time outside in the sun - or they could take vitamin D supplements, which are a safe and cheap way to increase levels'.

Fertility practitioner Zita West agrees. 'Vitamin D is becoming increasingly important for fertility', she told Marie Claire magazine, 'Having done over 800 vitamin D tests, we have found that around 70 percent of our clients are deficient'.

However, as West points out, vitamin D deficiency is linked to other health problems such as obesity, polycystic ovaries and immune disorders. This demonstrates that the link between vitamin D levels and fertility are not clear cut.