Vitamin D has many important roles in maintaining health in the body. Natural food sources of vitamin D are limited, but include fish such as cod or salmon, as well as eggs and beef liver. Milk, cereals and orange juice are often fortified with vitamin D as well. Alternatively, you can take a vitamin D supplement, but the primary source of vitamin D is the synthesis of it in the body when the sun's ultraviolet rays hit the skin. If you do not get a lot of sunlight, take a supplement or eat foods that contain vitamin D, you are at risk of vitamin D deficiency, and a lack of vitamin D can increase your risk for several health problems.
Increased Risk of Bone Disease
One of the roles of vitamin D is to help with the body's absorption of calcium, which helps strengthen bone structure. Because of this important role, the National Institutes of Health Office of Dietary Supplements explains that a deficiency of vitamin D may cause brittle bones that can become deformed. In children, this is referred to as "rickets," and in adults it is called osteomalacia. While rickets and osteomalcia are linked to long-term severe vitamin D deficiency, even a mild deficiency can lead to osteoporosis, or bone loss.
Increased Risk of Heart Disease
The fact that vitamin D regulates the body's calcium levels does not only affect the bones, but it also affects muscles, including the heart. Calcium helps regulate heart muscle contraction, and without proper regulation, the heart will be affected. The October 2008 issue of the "Journal of Clinical Endocrinology and Metabolism" reports a study conducted at the Medical University of Graz, Austria, which found that insufficient vitamin D increases the risk of heart disease, heart failure and sudden cardiac death.
Increased Risk of Diabetes
The March 2008 issue of "Diabetes, Obesity and Metabolism" reports that insufficient levels of vitamin D can negatively affect the production and release of insulin in the body, leading to the onset of diabetes. Lead author, X Palomer, from the Institut de Recerca in Barcelona, Spain, states that vitamin D regulates calcium levels, and calcium helps regulate the production and secretion of insulin, but vitamin D also has a direct effect on the functioning of cells in the pancreas, which is where insulin is produced.
Increased Risk of Cold and Flu
Low levels of vitamin D also increase your chances of catching a cold or flu virus. Vitamin D plays such a powerful role in maintaining a healthy immune system that the 2009 issue of the "Journal of Environmental Pathology, Toxicology and Oncology" published a report stating that health care workers should undergo testing to make sure they are not vitamin D deficient, especially at the onset of flu season or possible swine flu outbreaks. The relationship between vitamin D and flu lies in the fact that vitamin D is largely produced in the body from exposure to the sun, and outbreaks of flu occur when sun exposure is limited, such as during winter months.
Increased Risk of Cancer
Although researchers can't explain exactly why, a report in the January-February 2010 issue of "Cancer Journal" states that those with low levels of vitamin D have an increased risk of the development and progression of cancer cells, and the risk is not limited to one particular type of cancer. The report, submitted by the Roswell Park Cancer Institute in Buffalo, N.Y., does state that one way vitamin D appears to stop the progression of cancer is by encouraging cancer cell death.