Vitamin D is essential to humans because it aids in calcium absorption and helps regulate phosphorus and calcium in the blood. Vitamin D is not naturally found in many foods, but small amounts are in eggs, fish, and fish liver oils. People can also meet their vitamin D needs through sun exposure. People most at risk for vitamin D deficiency are infants who are exclusively breast-fed, people with naturally dark skin, the elderly, and those who use sunscreen on all exposed skin.
Children who do not get enough vitamin D can develop rickets, according to Oregon State University's Linus Pauling Institute. In children with rickets, the bones do not mineralize and cannot adequately bear weight. When this happens, the long bones of the arms and legs can have a bowed appearance. In infants with rickets, the soft spots on the skull may not close as quickly as normal and the ribcage can be deformed.
In severe cases of vitamin D deficiency, children can suffer from seizures, according to the Linus Pauling Institute. The seizures develop because of a condition called hypocalcaemia, in which serum levels of calcium are extremely low.
A condition called osteomalacia, also referred to as adult rickets, can develop in adults with significant vitamin D deficiencies. With osteomalacia, bone mineral is depleted, causing bone pain and soft bones, according to the Mayo Clinic. Osteomalacia can also cause bones to break in only minor injuries. The condition is similar to osteoporosis because of the risk of bone injuries.
Muscle Pain and Weakness
Children and adults who are vitamin D deficient can experience muscle pain and weakness as a result. These symptoms can be signs of rickets and osteomalacia, but they can also occur before these conditions develop. In many cases, the pain and weakness is mild and is not noticeable early in the stages of the deficiency, according to the Office of Dietary Supplements.