Studies over the past few years have portrayed vitamin D as beneficial for a vast number of medical conditions: cancer, Alzheimer’s, multiple sclerosis, rheumatoid arthritis (RA), and chronic pain. However, a new study by researchers at a Canadian university suggests that this may not be the case.
Investigating ten beliefs about vitamin D
The researchers, led by Dr. Michael Allan, director of the evidence-based medicine department at the University of Alberta, analyzed previous studies about vitamin D to assess the reliability of the data as applied to 10 common beliefs about vitamin D. These beliefs included the prevention of falls and fractures; reduction of respiratory infections; depression and mental well-being; rheumatoid arthritis, multiple sclerosis; reduction in mortality; and reduction in cancer incidence and mortality. They also investigated the beliefs that more vitamin D is better and that vitamin D levels should be tested regularly.
When past studies were examined with a critical eye, many fell short. The only beliefs that received some support were a slight reduction in mortality in people more than 70 years of age, and the prevention of fractures (particularly when vitamin D is given with calcium). Dr. Allan pointed out that the latter was a small decrease, saying if someone took “1000 IU of vitamin D and 500mg of calcium as supplements every day for 10 years, a chance of fracture of 15 percent over 10 years would turn into 13 percent. Some people will look at turning a 15 percent risk into 13 percent as not very impressive, others will say it’s an important difference.”
There was no reliable evidence that vitamin D was beneficial in any of the other beliefs under scrutiny. In fact, there seems to be some indication that megadoses of vitamin D might actually increase the risk of falls in frail elderly people.
Flaws in study designs
The primary issue involved in the past studies related to bias and flaws in study design. Dr. Allan explains that “the research is mostly poorly designed from the get-go.” He used an example of research in depression and mental health where “they enrolled people into these trials to see if they could improve depression scores and the patients were not even depressed.”
Half of the 1,600 studies conducted in vitamin D over the past decade are cohort or observational studies. “These kinds of studies quite frequently demonstrated an association between low vitamin D and a higher risk of developing illness or a higher illness burden. Unfortunately, this research can show an association or a correlation, but it can’t show causation,” Dr. Allan said.
To adequately investigate the possible connection between vitamin D and its effect on health, studies should utilize randomized controlled trials (RCTs), and objective measures. Without this, it is impossible to draw any firm conclusions about causation between vitamin D and its impact on health.
What about vitamin D and rheumatoid arthritis?
Several studies on RA and vitamin D were reviewed. One cohort study showed an association between vitamin D and lower risk of developing RA. However, when looking at RCTs, no differences were found between people with RA and the control group. The authors conclude that there is a lack of consistent and reliable evidence for the effect of vitamin D on treating or preventing RA.
I asked Dr. Allan what he would say to someone with RA who is taking vitamin D or interested in taking it. “The present research does not support its utility in improving rheumatoid arthritis symptoms. If someone’s on it and they’re pretty sure they got a benefit, they might be a unique person. But I can’t recommend it for people who aren’t on it.” Dr. Allan added a caveat. “There is some benefit in fracture prevention and perhaps preventing falls. If you’re at risk for fractures and falls, maybe there is some advantage to continue to take vitamin D. It may not work for rheumatoid arthritis, but it may be working to prevent fractures and falls.”
This study provides an important objective assessment of the existing data for the impact of vitamin D on rheumatoid arthritis and other medical conditions. It is disappointing that so many of the studies that have supported this link appear to be poorly designed and therefore delivered questionable data.
Unfortunately, this is the case with many treatments in complementary and alternative medicine. At best, there may be a few studies, but rarely any that utilize randomized controlled design. At worst, all we have is anecdotal information: people we meet say something worked for them, but there is no scientific investigation can give us actual facts. Without RCTs, it is impossible to draw a conclusion about a causative link between a particular alternative intervention – supplements, natural medicine, diet – and its impact on our health.
Over the last few years, I’ve seen an increase in people with RA using alternative regimens instead of or in addition to their RA meds. Some report a difference, others not. Hopefully the future will see high-quality studies of these treatments so we can add objective evidence to anecdotal reports.
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Lene writes the award-winning blog The Seated View. She’s the author of Your Life with Rheumatoid Arthritis: Tools for Managing Treatment, Side Effects and Pain and 7 Facets: A Meditation on Pain.
Lene Andersen is the Community Leader for HealthCentral’s RA Community. Lene (pronounced Lena) is an award-winning writer, health and disability advocate, and photographer living in Toronto. She’s written several books, including Your Life with Rheumatoid Arthritis: Tools for Managing Treatment, Side Effects and Pain, and 7 Facets: A Meditation on Pain, as well as the award-winning blog, The Seated View. Follow Lene on Twitter @TheSeatedView and on Facebook. Watch her story on HealthCentral.