Vitamin D strengthens bones by helping to maintain blood calcium and phosphorus levels and is important for the formation of new teeth and bones. Vitamin D deficiency in children can cause rickets, bone deformity and tooth damage. This deficiency in adults can cause osteoporosis, bone fractures and tooth decay. The risk of vitamin D deficiency is higher in infants, the elderly, people with dark skin, inadequate sunlight, impaired fat absorption, and inflammatory bowel disease and kidney failure. Sunlight is needed for the synthesis of vitamin D. Mushrooms, salmon, sardines, tuna and eggs are some of the sources of vitamin D.