Investigating vitamin D deficiency

Vitamin D plays an important role in calcium metabolism, bone mineralisation and muscle strength.¹ Over 90% of vitamin D is synthesised in the skin upon exposure to ultraviolet B radiation from sunlight, and the rest is obtained from the diet. Dietary sources of vitamin D include oily fish, liver, egg yolks, fortified margarine and fortified breakfast cereals. However, with the exception of fatty fish such as North Sea salmon, herring or mackerel, the vitamin D content of unfortified food is relatively low.² Risk factors for vitamin D deficiency are listed in the Box.