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A closer look: D3 has no effect on cardiovascular risk factors

Posted on: September 19, 2012   by  JA Larson

A closer look: D3 has no effect on cardiovascular risk factors

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Dr. Wood and colleagues from the University of Aberdeen recently reported that vitamin D has no effect on conventional cardiovascular risk factors. They published results from their randomized controlled trial in the Journal of Clinical Endocrinology and Metabolism.

Adrian D. Wood et al. Vitamin D3 Supplementation Has No Effect on Conventional Cardiovascular Risk Factors. A Parallel-Group, Double-Blind, Placebo-Controlled RCT. J Clin Endocrin Metab. First published ahead of print August 3, 2012 as doi:10.1210/jc.2012-2126

Let’s look at the who, how, and what:

Who

267 healthy 60-70 year-old Caucasian women who lived at home participated and completed the study. Subjects were seen every 2 months. “Healthy” means that folks with known diseases or problems were screened out.

How

There were 3 groups in the study, all doses administered for 12 months:

  • 400 IU D3
  • 1000 IU D3
  • No D3 (placebo)

They measured surrogate heart disease markers:

  • serum lipid profile
  • estimate of insulin resistance
  • inflammatory biomarkers
  • blood pressure

They also assessed: bone density, weight, waist circumference, activity levels, diet, and UVB exposure (with badges).

What

Mean baseline vitamin D level was 13-14 ng/ml in all three groups, so almost all were deficient or insufficient. After 12 months of supplementation, mean serum vitamin D levels were:

  • 400 IU:  25.9 ng/ml
  • 1000 IU:  30.3 ng/ml
  • Placebo:  13 ng/ml

The authors reported that risk factor levels varied by season in all groups independently of serum D levels; this raises issues about seasonality data in observational studies. As for their heart disease markers, they found no difference among any group. They concluded: “Improving vitamin D status through dietary supplementation is unlikely to reduce CVD risk factors.”

Analysis

The authors’ conclusion is stated in their title: “Vitamin D3 supplementation has no effect on conventional cardiovascular risk factors.” This title and conclusion overstates the actual finding. It would more accurate to say that 1000 IU/day or 400 IU/day for a year has no effect on cardiovascular risk factors, not that vitamin D has no effect.

The authors agreed that they may have had low D serum effects: “Additionally, vitamin D3 doses of 400 or 1000 IU may have been too low to have beneficial effects on surrogate markers of CVD risk.” Dr. Robert Heaney, for example, has suggested that a vitamin D level of 50 ng/ml should be considered the minimum threshold, a level that the 1000 IU group did not come close to.

The study was too small and for too short of time to look at actual cardiovascular disease (CVD) onset or events. Obviously CVD is a long latency disease and takes many years to develop.

Correlating low serum D levels with markers is basically correlating with a correlation, which is weaker than correlating with actual events. Excluding sick folks also distorts the sample.

I was disappointed that there was no discussion of their secondary data (activity, diet, bone density, UVB, etc.).

In summary, here is what I would highlight about this study:

  1. Low vitamin D doses raise serum vitamin D to low levels, which has little effect in the short-term on markers for CVD in healthy elderly women.
  2. The actual impact on CVD in healthy elderly women is unknown.

Why do researchers study low doses? All human use research has to be approved by committees who are typically very risk averse, though we are starting to see more and more trials using better and higher doses of vitamin D.

3 Responses to A closer look: D3 has no effect on cardiovascular risk factors

  1. chrisb

    It amazes me when it is thought that low doses of anything will achieve anything of any significance; this applied to a Vitamin D study I read about a few years back for women with the potential for developing breast cancer, and where the supplementary dose was a measly 400ius per day. The studies authors concluded that there is no benefit whatsoever. We should bear in mind that some studies on nutrients, and possibly Vitamin D, are probably designed to fail from the outset and as portrayed in the media.

  2. Jim Larsen

    Human use research approval committees are risk averse because you can’y unring that bell. Remember Thalidomide?

    Lappe’s 2007 D and cancer research showed a positive result. http://ajcn.nutrition.org/content/85/6/1586.full

    Her Navy BCT and stress fracture research showed a positive result. http://www.ncbi.nlm.nih.gov/pubmed/18433305

  3. Jim Larsen

    Or look at this study. http://atvb.ahajournals.org/content/early/2012/08/30/ATVBAHA.112.248039.abstract?sid=05915f00-59b5-46de-b4e9-276517959e06

    http://www.nutraingredients.com/Research/Study-links-vitamin-D-to-heart-disease-and-early-death/?

    In this case, serum levels of 50 nmol/L (20 ng/ml) were strongly associated with lower mortality/CVD. A researcher designing a new study might look at that study and decide to use the approved IOM dosages to test that hypothesis.

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