Wednesday, October 28, 2009

Vitamin D and blood vessel health

I'm sure you know by now that vitamin D is the new darling of the vitamin world. If you're not taking extra, where have you been? UK investigators(1) tested blood vessel health in type 2 diabetics by an indirect method called flow mediated vasodilation or FMV and added yet another reason to consider letting a little sunshine onto your pasty white skin. And if your skin is not white, all the more reason to make an extra effort to get extra D by sun or by supplement-- darker skin is known to be more resistant to the effects of UV radiation with respect to the production of viratmin D.

First a review of FMV. This rather simple test measures the ability of the brachial artery located in the elbow to dilate in response to increased flow. A pressure gauge measures the force of blood flowing through this upper extremity vessel. A blood pressure cuff is then placed on the subject's arm and pumped up high enough to stop blood flow to the arm below. When released, the surge of blood returning to the artery causes the vessel to expand, accommodating an increased flow to the (briefly) oxygen-starved tissues of the lower arm.

This dilation is the mark of a healthy vessel. People with diabetes and hypertension have blood vessels that don't respond normally when tested--and also, unfortunately, in real-life situations such as exercise. Researchers, therefore, use this test to evaluate certain interventions like medications, vitamins, or dietary strategies that tend to normalize the wacked-out FMVs of those with such chronic conditions.

So Dr. Sugden and his colleagues took a group of sun-starved, diabetic Scots in winter and gave them a single whopping dose of D--100,000 units--testing their FMVs before and 8 weeks after the bolus. All of these subjects had D levels <50 ng/ml prior to the trial, and the D supplement raised their levels on average by 15. Darned if that D didn't do the duty! FMV levels rose significantly at follow-up.

Have you D-cided to up your D yet?

( 1)Sugden, JA et al. Vitamin D improves endothelial function in patients with Type 2 diabetes mellitus and low vitamin D levels. Diabet Med. 2008 Mar;25(3):320-5. Epub 2008 Feb 13.


laura said...

Not to be sarcastic, but do you think the vitamin D levels that are decreased come from
1 Age over 65 that missing enzyme

2 Statins and there ability to eliminate D production by a certain pathway

Medicine would not be where it is today if it weren't for those of us who do not live such a healthy lifestyle.

Iam having a senior moment. I can't think of anything more to say. Carry on.

Medtipster said...

Great write up about the super-cool benefits of Vitamin D. Do the benefits apply to all ages or is it restricted to certain age groups? Is Vitamin D just as effective among persons who are terminally ill as it is with relatively healthy people?