Vitamin D and Neuromuscular Function

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Curr Rheumatol Rep. 2005 Oct;7(5):356-64.

Vitamin D: more than just affecting calcium and bone.

Staud R.

University of Florida, PO Box 100221, 1600 SW Archer Rd, D2-39,

Gainesville, FL 32610-0221, USA. .

Vitamin D is a fat-soluble steroid that is essential for maintaining

normal calcium metabolism. In vitamin D deficiency, calcium

absorption is insufficient and cannot satisfy the body's needs.

Consequently, parathyroid hormone production increases and calcium is

mobilized from bones and reabsorbed in the kidneys to maintain normal

serum calcium levels--a condition defined as secondary

hyperparathyroidism. Most organs, including the gut, brain, heart,

pancreas, skin, kidneys, and immune system have receptors for 1,25

(OH)vitamin D. Furthermore, all of these organs have the capacity to

synthesize 1,25 (OH)vitamin D from vitamin D. Extensive research

suggests that vitamin D deficiency is common and represents a global

health problem. Clinical consequences related to low vitamin D levels

include not only osteomalacia, osteoporosis, and rickets, but also

neuro-muscular dysfunction and fractures. Falls related to

neuromuscular dysfunction lead to 40% of all nursing home admissions

and are the largest single cause of injury-related deaths in elderly

people. About one-third of all persons 65 and older fall at least

once a year, resulting in more than 1.5 million emergency room

treatments and more than 300,000 hospitalizations. Falls cause more

than 11,000 deaths per year, most of them in elderly patients (>/= 75

years) who suffer hip fractures. It is well established that vitamin

D deficiency not only has serious consequences for bone health, but

also for other organ systems. Previous studies have shown that

vitamin D supplementation reduces the number of fractures and

directly improves neuromuscular function, thus helping to prevent

falls and subsequent fractures. In addition, vitamin D appears to

have other important functions as a regulator of cell differentiation

and cell growth.