What is vitamin D deficiency? Vitamin D deficiency is a common condition in which the body has inadequate stores of vitamin D. This fat-soluble vitamin is produced in the skin as a result of exposure to the sun’s rays, which are the main source of vitamin D. Vitamin D is also available in dietary supplements and in liver, eggs, oily fish, and fortified milk and dairy products. Vitamin D is essential for many aspects of health, including the absorption of calcium and phosphorus from food and the building of strong bones. Vitamin D is also important for hormone regulation, inflammation reduction, and the optimal functioning of the nervous system and the immune system. It is critical for normal development and growth of cells, bones and teeth. Vitamin D deficiency is far more common than once believed. The sun’s rays are the primary source of vitamin D, and lifestyle changes have made it difficult for many people to get enough time in the sun. Reasons for limited sun exposure include working indoors, as well as using sunscreen and avoiding the sun to prevent skin cancer. People who live in Northern latitudes also have difficulty getting enough vitamin D because in these areas the sun’s rays are not strong enough during winter months to allow the skin to produce sufficient amounts of vitamin D. Untreated vitamin D deficiency can lead to serious complications, such as bone fractures and bone deformities. Vitamin D deficiency has also been linked to a variety of serious conditions, such as certain cancers and cardiovascular disease. Seeking regular medical care and following your treatment plan can help reduce the risk of serious complications from vitamin D deficiency.