My son had some blood tests last week and I got a call this morning from our surgery to say he has a vitamin D deficiency and we have to make an appointment with the pharmacist to discuss. Does anyone know if there are any other causes of Vit D deficiency other than lack of sunlight. My son is very sporty so outside a lot, walks everywhere and his diet contains foods rich in vitamin D, so I'm a little confused as to why his levels would be low, maybe he's staying in the shade too much?