Osteoporosis: calcium and vitamin D

Published on January 19, 2015   33 min

Other Talks in the Series: Bone in Health and Disease

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Hello, my name is Bo Abrahamsen. I'm a professor at the University of Southern Denmark and the Research Center for Aging and Osteoporosis in Glostrup Hospital, Copenhagen. My talk today is Osteoporosis Calcium and Vitamin D. And I will try to talk about some studies that I think may be familiar to you. So it may be you'll find you'll have to go back and perhaps read the paper in question to fully understand what I'm getting at, so maybe one or two places. I'm not giving a lot of introduction. But rather, assume that you may have already read the papers. Because they've been really widely discussed in the past years.
These are my disclosures. I'm not speaking on behalf of any of the organizations listed here at all.
As you probably know, there's difference in fracture risk in different parts of the world. And there's a little bit of a tendency for fractures to be rarer the nearer you get to the Equator. So that would of course drive the hypothesis that perhaps the lack of vitamin D in the Northern and Southern Hemisphere as you get away from the Equator would be one of the reasons there are more fractures. So if you look at the right hand of the slide, you'll see rates from the International Osteoporosis Foundation. And as you can see, Argentina, Iceland, and Norway all have fairly high fracture rates, whereas Central Africa and the northern part of Latin America all have low rates. And these are the very sun-rich areas of the world. But you can also see fairly high rates of fractures in the Middle East and in the European and Asian part of Turkey.
It's been difficult to show any convincing effects of vitamin D supplementation in the general population on bone mineral density. As you know, bone mineral density is an important risk factor for fracture. It's not the only one, but it's a really important one. And there was a really nice meta-analysis in The Lancet this year looking at a number of intervention trials. And then on the left part of the chart showing the mean difference in numbers on BMD with supplementation this is percent change in lumbar spine BMD. And as you can see, the average increase is zero. If you look at the right hand, you have the chart, you have the femoral neck BMD where there is a small significant increase, but of less than 1%. And you may know that a standard deviation of BMD is about 10% or 11%. And that's the order of a change that's needed to reduce fracture risk by half. So these are quite small and quite, perhaps, inconsistent findings. The authors conclude that this systematic review provides very little evidence of an overall benefit of vitamin D supplementation on bone density. They also conclude that there's a small BMD benefit potentially at the femoral neck. But they also find signs of significant publication bias as assessed by funnel plots. And you also notice significant heterogeneity between studies statistically. So there's no clear BMD effect in the general public of vitamin D supplementation, though of course as clinicians, we know that in an individual patient who is vitamin D deficient, the response in BMD can be huge.