Skepticism re widespread vitamin D supplementation
Dr. Lenore M Buckley, Bruce Jancin, SNOWMASS, CO
extra calcium absorption may not all go to bones
some calcium may add to atherosclerotic plaques-->incr CV events
(per Buckley at American College of Rheumatology symposium)
worrisome for pts with CAD or high risk incl: RA, SLE, DM, psoriasis
RECENT CROSS-SECTIONAL STUDY
340 African Americans with type 2 diabetes
serum 25-hydroxyvitamin D levels assoc w incr calcified atherosclerotic plaque
in aorta and carotids
(J.Clin.Endo.Metab. Jan. 8, 2010; Epub ahead of print PMID:20061416).
LARGE PROSPECTIVE RANDOMIZED TRIAL
assessed effects of Ca+ supp on vasc event rates
no African Americans in study
n = 1,471 healthy postmenopausal New Zealand women
received either Ca+ or placebo
followed 5 yrs
101 MIs, CVAs, and sudden deaths in
69 in Ca+ group, 54 events in 42 control subjects
vascular event rate was higher in women with high compliance with calcium supplementation
event rate was higher during months 30-60 of follow-up
(expected initial latent period)
(Br. Med. J. 2008;336:262-66).
NNT = NUMBERS NEEDED TO TREAT
Buckley thought these were disturbing
NNT for 5 yrs Ca+ to cause 1 MI (compared to placebo) was 44
NNT for 1 stroke: 56
NNT to cause 1 more CV event: 29
NNT to prevent one symptomatic fracture: 50
more docs are ordering Vit D testing
incr driven by hope that it might protect vs: CA, dementia, AI, CV dz
(in my view it is protective vs viruses ie flu, poss also bact, def also CA,
but I know of no one who claims it protects vs CV dz or dementia)
it is one of the most-ordered lab tests in US now
test isn't that reliable and isn't cheap
here costs $50, range given in article is $40-200
there is no consensus on optimal blood level
vit D testing is covered by medicare-->
but according to Buckley they're talking about not covering
vitamin D supp reduces fracture risk in elderly, esp pts w low serum levels
The trouble is, that hope is driven mostly by epidemiologic data, which must be viewed as hypothesis-generating rather than definitive. The classic example of how misleading epidemiologic associations can be is the expectation that estrogen replacement would reduce cardiovascular risk in postmenopausal women; when the Women’s Health Initiative and other prospective trials were eventually carried out, it turned out just the opposite was true, Dr. Buckley noted.
“The question we have to ask is: What does that low serum vitamin D level mean? Is it the thing that predisposes, or is it somehow a byproduct of illness?” she continued.
There is intriguing evidence to indicate the optimal level of vitamin D to promote bone health, muscle strength, immunity, and other key functions may vary by race. Data from the National Health and Nutrition Examination Survey show that very few Caucasian children ages 1-12 years are vitamin D-deficient using the classic threshold of 15 ng/mL. In contrast, about 10% of non-Hispanic black 1- to 6-year olds are vitamin D-deficient, as are close to 30% in the 7-12 age bracket (Pediatrics Sept. 2009; e362-370; doi:10-1542/peds.2009-0051).
Many observers see this racial disparity as a public health problem reflecting unequal access to services. But there is a conundrum here: If vitamin D deficiency is rampant in black children, why do they have greater bone strength and muscle mass than Caucasians?
“It makes one wonder whether the definition of normal levels should vary by race,” according to the rheumatologist.
Support for this notion comes from studies showing that pushing serum vitamin D levels to 30 ng/mL or higher in Caucasians reduces their parathyroid hormone levels, while pushing levels above 20 ng/ml in African Americans – young or old – doesn’t further decrease parathyroid hormone or increase bone density.
Asked by audience members what she does about vitamin D in her own practice, Dr. Buckley said she generally tries to get patients into the 20-29 ng/mL range, while in African Americans and patients with known cardiovascular disease she aims for 15 ng/mL or slightly more “and I worry that might be too high sometimes.”
She reserves expedited supplementation – 50,000 IU weekly for 8 weeks – mainly for vitamin D-deficient elderly patients at high risk for fracture or fall. That’s where there is supporting evidence of benefit. There is no evidence to support supplementation in young or middle-aged patients, whose increased fracture risk is decades away.
Like many others, Dr. Buckley eagerly awaits fresh guidance in the form of updated recommendations on vitamin D from the Institute of Medicine. Rumor has it that the IOM report, due this spring, will recommend an increase in the currently recommended supplemental 400 IU/day for 50- to 70-year-olds not getting sufficient vitamin D from the sun. Her hope is the IOM will address the thorny issues of who should receive supplementation, and how fast it should be done.
Dr. Buckley reported having no financial relationships relevant to her talk.
Dr Milner/cardiology says high vitamin D increases heart dz/fibrosis