The study, presented at the American Society of Anesthesiologists 2007 Annual Meeting in San Francisco, found that one in four patients who suffer from chronic pain also have inadequate blood levels of vitamin D. As such, the researchers put forth that the vitamin D deficiency possibly contributed to the patients' ongoing pain. Vitamin D deficiency - which can lead to osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases - s been found to be lacking particularly in inhabitants of colder climates. A recent study, for example, indicated that the median adult intake of vitamin D in the US is only 230 IU per day, versus the researchers' recommended 2000 IU per day. The latest study, undertaken at the Mayo Comprehensive Pain Rehabilitation Center in Rochester, Minnesota, involved 267 adults undergoing outpatient treatment for chronic pain. The researchers recorded their serum vitamin D levels, pain medication (morphine), as well as general health, and found patients lacking sufficient vitamin D also required higher doses of morphine for a longer period of time. Of these patients, 26 per cent had vitamin D inadequacy and needed almost twice the dose of morphine of the group with adequate vitamin D levels. The vitamin D inadequacy group were also reported as using morphine for an average of 71.1 months compared to 43.8 months for the other group. As well, the vitamin D deficient group showed lower levels of physical functioning and poorer overall health. "…this is the first time that we have established the prevalence of vitamin D inadequacy among a diverse group of chronic pain patients," said study author, Michael Hooten, medical director and anesthesiologist at the Mayo Comprehensive Pain Rehabilitation Center. However, inadequate levels of vitamin D has long been associated with causing pain and muscle weakness and studies have suggested that pain-related symptoms of vitamin D inadequacy respond poorly to pain medications. One possible outcome is supplementing patients with vitamin D. "The implications are that in chronic pain patients, vitamin D inadequacy is not the principal cause of pain and muscle weakness, however, it could be a contributing but unrecognized factor," said Hooten. Vitamin D inadequacy can be easily and inexpensively treated using a prescription supplement, once or twice a week for four to six weeks, according to Hooten. Deficiency in vitamin D affects inhabitants of colder climates, because sunlight induces synthesis of vitamin D in humans. As such, if a consumer is not getting adequate exposure to the sun for vitamin D and its subsequent impact on their serum 25 (OH)D levels, they should be supplementing with vitamin D. Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The former, produced in the skin on exposure to UVB radiation (290 to 320 nm), is said to be more bioactive. The latter is derived from plants and only enters the body via the diet.