A disease in children where softening of the bones is caused by a deficiency of vitamin D. Humans make vitamin D from the action of sunlight on the skin. It has been calculated that exposure of hands and face to sunlight for 10 to 15 minutes a day is enough to prevent rickets (136). The liver then stores the vitamin so ensuring an adequate source throughout the winter. Many everyday foods are now fortified with vitamin D – margarines, breakfast cereals and most brands of soya milk.