Benefits of 'Sunshine Vitamin' Not So Clear

By Pat Anson, Editor

Maybe Vitamin D isn’t all it’s cracked up to be.

We’ve reported on several studies showing that low levels of Vitamin D are linked to a variety of chronic pain conditions, as well as anecdotal reports that taking Vitamin D supplements can relieve pain and make you feel better.

But a Canadian researcher says there is very little evidence that the “sunshine vitamin” does any of that.

"Wouldn't it be great if there was a single thing that you or I could do to be healthy that was as simple as taking a vitamin, which seems benign, every day? There is an appeal to it. There is a simplicity to it. But for the average person, they don't need it," says Michael Allan, a professor of Family Medicine and director of Evidence Based Medicine at the University of Alberta's Faculty of Medicine & Dentistry.

Allan is the lead author of a review published in the Journal of General Internal Medicine that examines the evidence for 10 common beliefs about vitamin D. Those beliefs include the ability of vitamin D to prevent rheumatoid arthritis, treat multiple sclerosis, reduce falls and fractures, and improve depression.

The review found little evidence that Vitamin D supplements have much effect at all.

"Even areas that we really thought there was good evidence for benefit early on, don't seem to be bearing out," says Allan. "It makes it really difficult to determine a lot of time if there is anything substantial there that you could tell a patient, 'You can take this and it can help you this much.' There's really not nearly enough there to say that."

Allan and his colleagues did find evidence that Vitamin D can have an impact in reducing the number of falls and fractures among the elderly. But the effect is minor.

"Many people would say taking a drug for 10 years to stop one in every 50 fractures is probably not enough to be meaningful. And that's the best vitamin D gets as far as we know now," he said.

There have been over 1,600 studies conducted on Vitamin D in the last decade alone, but Allan says much of the research was poorly executed and is of low quality. He doesn’t dispute the overall health benefits of Vitamin D – such as building strong bones and teeth -- but thinks taking supplements is unnecessary and could even be harmful in large doses.

Most people get all the Vitamin D they need by being exposed to ultraviolet rays in sunlight. You can also get it by eating foods rich in Vitamin D, such as oily fish and eggs.

“Evidence does not support vitamin D supplementation for the treatment of multiple sclerosis and rheumatoid arthritis or for improving depression/mental well-being. Regular testing of 25-hydroxyvitamin D is generally not required, and mega-doses appear to increase harms,” Allan said. “Much of the evidence is at high risk of bias, with multiple flaws, including analyses of secondary endpoints, small and underpowered studies, inconsistent results and numerous other issues. Therefore, enthusiasm for a vitamin D panacea should be tempered.”

Despite the lack of evidence, belief in the benefits of vitamin D supplements remains strong. Allan believes much of it stems from misplaced trust in studies that show low vitamin D blood levels are linked with poor health. However, association does not prove causation.

"The 40 year old person is highly unlikely to benefit from vitamin D," says Allan. "And when I say highly unlikely, I mean it's not measurable in present science."

Low Levels of Vitamin D Linked to Fibromyalgia

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.