Sunlight boosts fertility in both men and women by increasing their levels of vitamin D, a study has found

Known as the sunshine vitamin, vitamin D is also key to balancing sex hormones in women and improving sperm count in men, according to researchers. For women, vitamin D helps boost levels of the female sex hormones progesterone and estrogen by 13% and 21% respectively, regulating menstrual cycles and making conception more likely. Men increase their fertility by going into the sun, too – because vitamin D is essential for the healthy development of each sperm’s nucleus. It also increases levels of the male sex hormone testosterone, improving a man’s libido. The vitamin’s effect on both male and female sex hormones may explain why conception rates fall in the winter and peak in the summer in Northern European countries. The study of nearly 2,300 men, also found that levels of testosterone and vitamin D peaked in August and were lowest in March, just after the winter. Women have been found to ovulate less – and their eggs have a reduced chance of implanting in the womb – in the winter months. Although vitamin D can be obtained in small quantities by eating oily fish, eggs and liver, about 80% of the amount the body needs is obtained via a chemical process that happens when the UVB rays in sunlight are absorbed by the skin.