Systematic review and meta-analysis of observational cohort and randomized intervention studies.
The Facts:
This is a “systematic review and meta-analysis of previously published observational studies and randomized controlled trials” which attempts to sum up the findings of a very large and diverse body of research.
The authors were attempting to discern the association of Vitamin D deficiencies with various causes of death.
This paper covered 73 observational studies (849,412 subjects) which looked at participants according to their circulating levels of Vitamin D and 22 clinical trials (30,716 subjects) which compared treatment with Vitamin D supplementation to either a placebo or a no treatment group.
In the observational studies, they divided participants into three groups (bottom, middle and top) according to their baseline level of circulating Vitamin D when beginning the study.
Compared to subjects in the upper group, those in the bottom third (i.e. lowest levels of plasma Vitamin D) were 35% more likely to die from cardiovascular disease, 14% more likely to die from cancer, 30% more likely to die from “non-vascular, non-cancer” death and 35% more likely to die from “all-cause” mortality.
In the clinical trials, relative risk for “all cause” mortality was decreased by 11% in the groups receiving Vitamin D3 supplementation.
Subjects receiving Vitamin D2 supplements were actually shown to be at a slightly (4%) increased risk of death, particularly in groups that received lower intervention doses or were supplemented for shorter periods of time.
Dr. Lane’s thoughts: Read this carefully! This is about D3 and only D3. D2 has no beneficial impact.
Blood plasma levels of Vitamin D (25-hydroxyvitamin D) are inversely associated with the risk of death. (Lower levels of Vitamin D are associated with increased risk of mortality). Use of vitamin D3 supplements significantly reduces overall mortality among seniors.
Use of Vitamin D2, at least in the studies reviewed by these authors, doesn’t appear to be very beneficial and MAY be associated with a slightly increased risk of mortality…possibly due simply to its reduced therapeutic effect compared to D3.
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