The reason why many couples seem to conceive while they are on holiday in a beach may have been explained by scientists: sunlight might be good for a man’s sperm.

New research has indicated that Vitamin D – which is produced by the human body when it is exposed to sun – is critical to the production of sperm, and that a lack of the nutrient may be linked to male infertility.

The findings, from a team at the Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire, suggest that boosting Vitamin D production, either by increasing exposure to sunlight or by taking dietary supplements, might improve fertility among men.