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.

Tuesday, October 27, 2009

Small thigh circumference and cardiac risk

Here's a new take on body build and health! We are all familiar with the apple/pear thing in that those who carry their weight around the waist in an apple-ish silhouette are at greater risk of heart disease than those whose excess pounds hang on their hips. These Danish researchers took the measurements one level lower(1); here's what they found:

Professor Berit Heitmann and company from Copenhagen's Research Unit for Dietary Studies took tape measure to thigh on over 2800 legs still attached to as many Danes, then followed the group for 12+ years checking out incidence of heart disease and death. Pipe cleaner thighs that fell short of 60 cm. (23.6 in.) in circumference were an independent risk marker for both unfortunate endpoints.

So what's the problem with skinny thighs? Two of our biggest muscles are contained therein, namely the quadriceps and the hamstrings. A loss of muscle mass could be a marker for inactivity or chronic disease such as COPD that prevents exercise. In fact, a Canadian study found that loss of mid-thigh muscle mass as measured by CT scanning was a better predictor of mortality in chronic pulmonary patients than a low body mass (both indicative of the wasting associated with lung disease).(2) Less muscle mass is also known to predispose to insulin resistance and type 2 diabetes as demonstrated by the elevated fasting blood sugars and cases of diabetes that we unexpectedly see in scrawny old ladies.

So should we be measuring thighs along with waistlines, blood pressures, and pulse rates (and also asking about physical activity, sleep habits, diet histories and domestic violence in the leftover minutes of annual physicals)? Says Australian epidemiologist Dr. Ian Scott in an editorial accompanying the Danish study: "Will this association help clinicians predict risk in individual patients more accurately than they already do using readily accessible and validated risk calculators? The answer is — we do not know."

I, for one, shall pass for now.
(1) Heitmann, BL et al. Thigh circumference and risk of heart disease and premature death: prospective cohort study. BMJ. 2009 Sep 3;339:b3292. doi: 10.1136/bmj.b3292.
(2) Marquis, K et al. Midthigh muscle cross-sectional area is a better predictor of mortality than body mass index in patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med. 2002 Sep 15;166(6):809-13.

Thursday, October 15, 2009

Idiopathic erythema

My friends used to worry that my father, a psychiatrist, was secretly diagnosing their psychopathology when they'd stop by the house. On average, one word--adolescence--was all that was needed to label our deviance from normal behavior during those formative years.

Sometimes, I like to play 'guess the diagnosis' when I'm out and about in public. During PTA meetings at my daughter's high school, I'd sit and wonder why another parent's face was so red (the meeting content, as you may guess, was simply riveting!). I never did figure it out, nor do I have the slightest idea what happened to the man in the years since last we met. I was disturbed, however, to come across an item in a medical journal that suggested that his diagnosis may not have been benign.

Idiopathic erythema is a fancy way of saying the skin is red and we don't know why. One of my fellow residents during training had allergic dermatitis (eczema) as a cause of his not-so-idiopathic erythema. Those patients who are red for unknown reasons tend to be male (73%) and older (average age 69 years in one study).

Out of 218 Singaporeans studied by dermatologists there, 18% were ultimately found to have cancer. Dr. Steven Thng and his colleagues concluded, "We recommend close follow-up with reevaluation for malignancy even if the intitial investigation had been negative."

I hope this fellow is doing well, ruddy but cancer-free. But I now have something new to think about when a patient complains "Boy is my face red!"

Friday, October 02, 2009

Vitamin D, influenza, and old ladies

Many epidemiologists now believe that flu is seasonal because vitamin D levels fluctuate seasonally. Vitamin D is a potent immune modulator; individuals tend to have higher levels during summer months with higher exposure to UV radiation and, therefore, are less likely to contract the flu while sun-kissed.

Researchers followed the seasonal health adventures of 208 post-menopausal women over three years as correlated with their monitored intake of D.(1) The results, shown in the bar graph above, were as follows:
  • Those ladies in the placebo group (lightest bars) got cold and flu symptoms all year long, but especially in the winter.
  • The test subjects (intermediate shaded bars) who received 800 units/day of supplemental D were as likely to get sick in the summer as winter, but were far less likely to take to their beds than their D-ficient colleagues.
  • In the final year of the study, the test subjects were plied with 2000 units of D each day. Only one lady (as represented by the itty-bitty dark bar in summer) got sick while D-eeply dosed with the vitamin.
Presumably D same benefits accrue to old guys too.
1)Aloia JF, Li-Ng M: Epidemic influenza and vitamin D. Epidemiol Infect 2007; 135: 1095–1096.