Where does vitamin D come from?
Vitamin D (vitamin D3) is created in the skin when exposed to ultraviolet B radiation in sunlight. In the UK, between May and September, about 20 to 30 minutes a day spent outdoors in direct sunshine in the middle of the day will meet vitamin D needs for most fair skinned people1. Factors such as darker skin, the use of sunscreen, levels of pollution and the unpredictability of the British summer can all lower availability and between October and April, the level of ultraviolet is too low for vitamin D to be made.
There are dietary sources of vitamin D3 from fish and dairy products and vitamin D2 from plant sources, but at much lower levels than from sunlight. As a result, levels of vitamin D in the UK are generally low. The Department of Health reports that a quarter of the population have no more than a third of what is considered an adequate level