Vitamin D deficiency in childhood causes the diseaseĀ rickets wherein it is characterized by the weakening and softening of the bones in children because of impaired mineralization. Vitamin D functions to promote intestinal absorption of both calcium and phosphate; and the lack of vitamin D leads to the lack of calcium and phosphate, both of which are needed for bone formation. The adult counterpart of rickets isĀ osteomalacia which is caused by vitamin D deficiency in adults.