Vitamin D modulates calcium metabolism, which affects your bone health and muscle function. The contraction and relaxation of your muscles occurs in response to nerve stimulation that triggers rapid calcium flow between compartments within your muscle cells. This process, known as the calcium cycle, depends on normal concentrations of calcium. A low level of vitamin D in your body may lead to a reduced concentration of calcium, triggering muscle twitching and other musculoskeletal symptoms.
Vitamin D and Calcium
Vitamin D regulates active gastrointestinal absorption of calcium from your diet. A low level of vitamin D disrupts this absorptive process, leading to loss of a high proportion of dietary calcium in your stool. Because calcium is essential to many body functions, poor absorption of this mineral provokes bone breakdown to compensate. With a severe or long-standing vitamin D deficiency, your blood calcium level may drop to an abnormally low level, a condition called hypocalcemia.
Vitamin D Deficiency and Muscle Function
Vitamin D deficiency may lead to muscle twitching by causing hypocalcemia. A low calcium level leads to irritability of your muscle cells and involuntary contractions, also known as twitching or spasms. Muscle twitching related to vitamin D deficiency most commonly occurs in your hands, feet and face. In addition to twitching, you may experience muscle aches and progressive weakness. Muscle weakness and pain caused by a vitamin D deficiency is known as osteomalacic myopathy.
Skin and Vitamin D
Your skin cells possess the chemical machinery to produce vitamin D when exposed to ultraviolet light from the sun. Spending most of your time indoors, living in a location with limited sun and wearing clothing that covers most of your skin may severely limit the amount of vitamin D your body produces, potentially contributing to a deficiency. Your skin's capacity to produce vitamin D decreases as you age, which may also contribute to the development of a deficiency.
If you are otherwise healthy, you can prevent the development of a vitamin D deficiency by consuming a diet that supplies the recommended adult intake of 600 IU or 15 mcg daily. After age 70, your daily requirement for vitamin D increases to 800 IU or 20 mcg. Foods that provide you with vitamin D include egg yolks, salmon, mackerel, sardines, tuna, liver, fortified milk and vitamin D-fortified cereal and fruit juice. Cod liver oil is a source of concentrated vitamin D. In addition to muscle twitching and aches, vitamin D deficiency may cause bone pain and increase your risk of fractures.
If you have persistent muscle twitching, see your doctor. Many conditions other than vitamin D deficiency can cause this symptom. Determining the correct diagnosis is essential to providing the proper treatment for your condition.