Vitamin D is a fat-soluble vitamin that you can obtain from food or synthesize in your skin when it is exposed to ultraviolet rays. It performs many vital functions to maintain healthy bone growth and development, a strong immune system and normal blood calcium and phosphorus levels. Despite its many benefits, too much vitamin D can cause negative health consequences.
Cell Differentiation
Cell division and proliferation help heal wounds and promote growth in your body. Cell differentiation is the process of changing the functions of cells that perform less specific tasks to those that perform specific tasks. This process leads to a decrease in cell proliferation. Uncontrolled proliferation can lead to mutation which causes cancer. Thus, vitamin D inhibits proliferation and stimulates the differentiation of cells, according to the Linus Pauling Institute of Oregon State University.
Calcium Regulation
When blood calcium drops below normal levels, your parathyroid gland secretes parathyroid hormone, or PTH, into your bloodstream. This triggers your kidneys to produce a type of enzyme that makes vitamin D. This causes your body to absorb more calcium from food in your intestines, to remove some calcium from bones, and deposits it into your bloodstream. If you blood calcium level is too high, vitamin D also helps reabsorb calcium into your bones.
Blood Pressure Control
Vitamin D plays a role in regulating blood pressure by interacting with the renin-angiotensin system. Renin is an enzyme that splits a peptide called angiotensin I from a larger protein produced by your liver. This peptide gets converted to angiotensin II which constricts small arteries and increases the retention of sodium and water in your bloodstream. A lack of vitamin D reduces the gene expression in renin that initiates blood pressure regulation.
Toxicity and Deficiency
Deficiency in vitamin D can cause rickets in children and osteomalacia in adults. Rickets causes bone growth deformity in children, particularly in the rib cage, arms and legs. It inhibits a child's ability to walk, stand or breathe properly due to the compression of the lungs and diaphragm. In osteomalacia, the bones are unable to reform themselves due to a lack of vitamin D. This causes bone pain and the bones to become softer, according to the Mayo Clinic.
Too much vitamin D can cause an overabundance of calcium in the bloodstream, causing calcium deposits in your muscle tissues, joints, kidneys and heart. This leads to calcification in your soft tissues that makes your joints less mobile and painful to move. Vitamin D toxicity can cause kidney stone development in your kidneys from excess calcium deposits.
Recommended Intake
Although your skin synthesizes vitamin D, you can still obtain vitamin D in your diet if you do not get enough sunlight exposure. The Mayo Clinic recommends you obtain no more than 1 mg of vitamin D daily. Eight ounces of milk contain about 2.5 mcg of vitamin D, while most canned fish contain about 6 mg of vitamin D. Other good food sources of vitamin D include cheese, yogurt, salmon, mackerel and fortified cereals.
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