By Pat Anson, Editor

Some recent studies are highlighting the importance of the "sunshine vitamin" -- Vitamin D -- in maintaining overall health, as well as possible links to fibromyalgia, rheumatoid arthritis and other chronic conditions.

Low levels of serum vitamin D were found in over 1,800 fibromyalgia patients with chronic widespread pain, according to the results of a meta-analysis (a study of studies) published in the journal Pain Physician.

Researchers at National Taiwan University Hospital found a “positive crude association” between chronic widespread pain and hypovitaminosis D, which is caused by poor nutritional intake of Vitamin D, inadequate sunlight exposure or conditions that limit Vitamin D absorption.

The most severe type of hypovitaminosis D causes general body pain, especially in the shoulder, rib cage, lumbar and pelvic regions.

A number of previous studies have explored the association between hypovitaminosis D with widespread musculoskeletal pain, including fibromyalgia, but the results were inconclusive. Fibromyalgia is a poorly understood disorder that is characterized by deep tissue pain, fatigue, depression and insomnia.

According to the Vitamin D Council, low levels of Vitamin D could be the result of fibromyalgia, rather than the cause of the disease.

Vitamin D helps control levels of calcium and phosphate in the blood and is essential for the formation of strong bones and teeth. Vitamin D also modulates cell growth, improves neuromuscular and immune function, and reduces inflammation

Sources of Vitamin D include oily fish and eggs, but it can be difficult to get enough through diet alone. Ultraviolet rays in sunlight are a principal source of Vitamin D for most people.

Taking Vitamin D supplements can improve exercise performance and lower the risk of heart disease, according to the findings of a small study at Queen Margaret University in Scotland presented at the Society for Endocrinology annual conference in Edinburgh.

Researchers gave 13 healthy adults Vitamin D supplements or a placebo daily for a period of two weeks.

The adults supplemented with Vitamin D had lower blood pressure compared to those given a placebo, as well as lower levels of the stress hormone cortisol in their urine. Previous studies suggest that Vitamin D can block the action of an enzyme which is needed to make cortisol.

A fitness test found that the group taking vitamin D could cycle 6.5km (about 4 miles) in 20 minutes, compared to just 5km at the start of the experiment. Despite cycling 30% further, the Vitamin D group showed lower signs of physical exertion.

"Our pilot study suggests that taking vitamin D supplements can improve fitness levels and lower cardiovascular risk factors such as blood pressure", said Dr. Raquel Revuelta Iniesta, co-author of the study. "Our next step is to perform a larger clinical trial for a longer period of time in both healthy individuals and large groups of athletes such as cyclists or long-distance runners.”

Around 10 million people in England have low vitamin D levels. On average, one in ten adults has low levels of vitamin D in summer, compared to two in five in winter. Because people with darker skin are less efficient at using sunlight to make vitamin D, up to three out of four adults with dark skin are deficient in winter.

"Vitamin D deficiency is a silent syndrome linked to insulin resistance, diabetes, rheumatoid, and a higher risk for certain cancers,” said lead author Dr. Emad Al-Dujaili. "Our study adds to the body of evidence showing the importance of tackling this widespread problem.”

Danish researchers recently reported that exposure to sunlight may delay the onset of multiple sclerosis (MS). Patients who spent time in the sun every day during the summer as teenagers developed the disease later in life than those who spent their summers indoors.