A vitamin D deficiency - usually the result of staying out of the sun - may be the key to a range of neuromuscular diseases, such as multiple sclerosis, Parkinson's and myasthenia gravis.
Elderly people who are frail and at risk of falling should also be given vitamin D supplements, says Illeane Howard, from the University of Washington school of medicine.
Dr Howard says that vitamin D deficiency is common in neuromuscular diseases and neurological disorders. She says the association is probably complex, but she urges doctors to look at vitamin D levels in patients with neurological disorders, and offer supplements when necessary.
(Source: proceedings of the annual meeting of the American Association of Neuromuscular & Electrodiagnostic Medicine)