MedicalResearch.com Interview with:
Michael Allan, MD CCFP
Professor of Family Medicine and
Director of Evidence Based Medicine
Faculty of Medicine & Dentistry
University of Alberta
MedicalResearch.com: What is the background for this study?
Dr. Allan: A large volume of observational (lower-level) research links lower Vitamin D levels with a long list of health concerns. Other non-clinical studies show the biochemical and physiological actions of Vitamin D could impact many health states. These factors have led many clinicians and scientists to advocate strongly for Vitamin D supplementation. However, this type of research can draw false connections. Therefore, we must examine high-quality randomized studies to determine if Vitamin D supplement can help people live longer, have improved health or avoid negative health outcomes.
MedicalResearch.com: What are the main findings?
Dr. Allan: We examined 10 specific areas, considering only the highest-level evidence. There is some evidence that regular use of Vitamin D ≥800 IU, with calcium (perhaps around 500mg), will reduce fracture risk. For example, if your chance of fracture was 15% over 10 years, taking vitamin D and calcium would reduce the risk to around 13% over 10 years. Vitamin D supplementation probably reduces the risk of falls in those at highest risk but the evidence is less reliable. Mortality may also be reduced but, if real, the difference would be small. For example, if a person has a 10% chance of dying in 10 years, taking Vitamin D every day for 10 years may reduce that risk to 9.5%. These positive effects were generally derived in populations over age 50 and most are over 65. There was no reliable or consistent evidence that Vitamin D prevents cancer, rheumatoid arthritis, or respiratory infection. There was also no reliable or consistent evidence that vitamin D improves multiple sclerosis, rheumatoid arthritis or depression/mental well being. Furthermore, mega-doses (≥300,000 IU taken once in autumn) seem to increase falls and/or fractures. Lastly, evidence does not support testing Vitamin D levels in the general population.
MedicalResearch.com: What was most surprising?
Dr. Allan: Much of the research was poor quality or had significant limitations. For example, of 11 randomized studies on low mood/depression, eight allowed inclusion of patients who were not depressed.
MedicalResearch.com: What should readers take away from your report?
Dr. Allan: Vitamin D may still be appropriate for older patients (example ≥50 years old), particularly those willing to take medicines for small reduction in fracture risk or those at high risk of falls. For younger adults, Vitamin D likely provides no meaningful or measurable benefit in health.
MedicalResearch.com: Is there anything else you would like to add?
Dr. Allan: Clinicians and patients should be aware that while lower-level evidence presents some compelling justification for regular Vitamin D supplementation, the potential benefits may be limited to small changes in falls and fractures for those at risk. Unfortunately, high level evidence fails to show convincing proof Vitamin D can have a meaningful improvement of health for adults.
MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.
G. Michael Allan, Lynda Cranston, Adrienne Lindblad, James McCormack, Michael R. Kolber, Scott Garrison, Christina Korownyk. Vitamin D: A Narrative Review Examining the Evidence for Ten Beliefs. Journal of General Internal Medicine, 2016; 31 (7): 780 DOI: 10.1007/s11606-016-3645-y
Note: Content is Not intended as medical advice. Please consult your health care provider regarding your specific medical condition and questions.
More Medical Research Interviews on MedicalResearch.com.