Supplemental Vit D? Meh!

The randomized trials of vitamin D and cardiovascular disease and diabetes have been, in general, quite inconsistent and inconclusive.

Whether the trials are of vitamin D alone or of vitamin D plus calcium, the results have been mixed and generally neutral and null, not showing a clear association.

So until we have more evidence from randomized trials that really assess the long-term balance of benefits and risks, it may be best — the most evidence-based and wisest approach — to use the Institute of Medicine’s recommendations for vitamin D that are based on bone health. These are intakes of 600 IU/day for patients 1-70 years of age and intakes of 800 IU/day for patients 70 years of age and above, and blood levels of 25-hydroxyvitamin D of 20 ng or higher, which should meet the needs of at least 97.5% of the population in maintaining bone health. For understanding whether high-dose vitamin D has benefits beyond bone health and whether it prevents cardiovascular disease, diabetes, cancer, and many other nonskeletal health outcomes, the randomized trials of 2000 IU/day and even higher doses are in progress, and results should be available in several years.

Amplify’d from www.medscape.com

Does Vitamin D Prevent Cardiovascular Disease and Diabetes?

JoAnn E. Manson, MD, DrPH

I would like to talk to you today about whether vitamin D prevents cardiovascular disease and diabetes, or whether the jury is still out. Many of our patients are taking high doses, even megadoses, of vitamin D: 4000-6000 IU a day or even more with the hope and expectation that these high doses will prevent heart disease, stroke, diabetes, hypertension, and many other nonskeletal chronic disease outcomes. But do we know that vitamin D in high doses has these benefits?

Several recent reports have shed light on these issues. One of these reports was a commentary written by myself and a colleague of mine (both members of the Institute of Medicine committee on dietary recommendations for vitamin D) and published in JAMA
[1] about 2 weeks ago. The other was the clinical practice guidelines from the Endocrine Society published in The Journal of Clinical Endocrinology & Metabolism.[2] Both of these reports concluded that the evidence that vitamin D prevents cardiovascular disease and most other nonskeletal health outcomes continues to be inconclusive and inconsistent.

In our commentary in JAMA, we reviewed the studies that have been conducted on this question. Most of the research has been observational. We know that association does not prove causation and that factors such as obesity or physical activity associated with higher levels of sun exposure can confound the relationship between 25-hydroxyvitamin D and the risk for diabetes or cardiovascular disease.

The randomized trials of vitamin D and cardiovascular disease and diabetes have been, in general, quite inconsistent and inconclusive. Whether the trials are of vitamin D alone or of vitamin D plus calcium, the results have been mixed and generally neutral and null, not showing a clear association. Most of these trials tested lower doses of vitamin D. However, we don’t yet know that higher doses (2000 IU/day or higher) will have a favorable benefit/risk ratio.

We can’t assume that more is better. More is not necessarily better when it comes to vitamin D, calcium, or many other nutrients. In fact, with vitamin D, there is a suggestion of a U-shaped relationship between 25-hydroxyvitamin D and risks for cardiovascular disease and all-cause mortality. There is a suggestion of increased risk at both low and very high levels of 25-hydroxyvitamin D.

So until we have more evidence from randomized trials that really assess the long-term balance of benefits and risks, it may be best — the most evidence-based and wisest approach — to use the Institute of Medicine’s recommendations for vitamin D that are based on bone health. These are intakes of 600 IU/day for patients 1-70 years of age and intakes of 800 IU/day for patients 70 years of age and above, and blood levels of 25-hydroxyvitamin D of 20 ng or higher, which should meet the needs of at least 97.5% of the population in maintaining bone health. For understanding whether high-dose vitamin D has benefits beyond bone health and whether it prevents cardiovascular disease, diabetes, cancer, and many other nonskeletal health outcomes, the randomized trials of 2000 IU/day and even higher doses are in progress, and results should be available in several years.

Read more at www.medscape.com

 

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