Interesting study, what I found interesting is that for levels above 43 ng/ml of vit D there is no added benefit as far as CVD (but of course we know that for other conditions like cancer a higher level would be optimal):
Death, CVD Risk Declines in People Who "Normalize" Vitamin-D Levels
March 18, 2010 (Atlanta, Georgia) — Adding heft to the hypothesis that vitamin-D deficiency is linked to cardiovascular disease, a new study has found that people with low vitamin-D levels who managed to normalize their levels were significantly less likely to develop cardiovascular events over up to six years of follow-up.
The study was presented as a poster by Dr Tami L Bair (Intermountain Medical Center Heart Institute, Murray, UT) earlier this week at the American College of Cardiology (ACC) 2010 Scientific Sessions.
According to coauthor Dr Joseph B Muhlestein (Intermountain Medical Center Heart Institute), the study looked at baseline and subsequent vitamin-D levels in 9491 subjects with known vitamin-D deficiency, rechecked their vitamin D, then compared subsequent rates of death, coronary artery disease, MI, heart failure, stroke, and renal failure among those who managed to bring up their vitamin-D levels with those who remained vitamin-D deficient. A cut point of <30 ng/mL was used to define vitamin-D deficiency.
"This wasn't a randomized trial, but all of these patients started with low vitamin D, and then the question is, if they treated their vitamin D, did it have an effect? We don't know what they did . . . the presumption is that they were told their vitamin D was low, then started supplementation or got their swimsuit out and went into the sun a lot to treat it."
Getting to Normal
After a mean of one-year of follow-up, those who had normalized their vitamin-D levels were significantly less likely to have died, developed heart failure, or developed coronary artery disease. A composite end point, looking at all outcomes combined, showed a highly statistically significant reduction among those with normalized vitamin-D levels.
Muhlestein drew particular attention to the 30% reduced risk of death in the normalized vitamin-D group. "A 30% reduction in risk is about the same you could hope to get from taking a statin or treating your blood pressure, so we thought it was certainly promising. It doesn't eliminate the need for a real randomized trial, although I'm trying to figure out a good way to do one."
There are a number of vitamin-D trials under way, most notably VITAL, a National Institutes of Health (NIH) study, launched in January.
But Muhlestein is concerned that the NIH trial may come up empty-handed for two reasons. For one, the trial, he says, is not measuring baseline levels or checking whether patients actually reach the optimal vitamin-D range in the intervention arm. "I can see why they aren't [measuring vitamin D at baseline], because if they find vitamin D is deficient is it ethical to say, 'I want you to stay vitamin-D deficient'?"
Vitamin-D deficiency is already known to increase the risks of skeletal disease, he notes. But without knowing if participants actually normalize their levels, it will be impossible to link normalization with an effect on events.
