Tag Archives: Vitamin D

Vitamin D2 or D3 as a supplement?

Vitamin D3 seems like the better choice for supplementation.

Despite considerable research, the health benefits of vitamin D 
supplementation in the general population remain controversial. In 
this systematic review and meta-analysis, investigators determined 
whether blood vitamin D levels and vitamin D supplementation were 
associated with risk for death.

One analysis involved 73 observational studies (mean follow-up, 0.3–
29 years) that involved 850,000 participants (median age, 63; median 
baseline blood 25-hydroxyvitamin D [25(OH)D] level, 20.7 ng/mL). 
Overall, compared with participants whose blood 25(OH)D levels were in 
the top third, those whose levels were in the bottom third had 
significantly greater risks for cardiovascular (CV)-related death 
(adjusted relative risk, 1.4), cancer-related death (ARR, 1.1), and 
all-cause death (ARR, 1.4). For each 10 ng/mL lower increment of 25(OH)
D, risk for all-cause death increased by 16%.

Another analysis involved 22 randomized, placebo-controlled trials 
(31,000 older participants; mean follow-up, 0.4–6.8 years) with data 
on the effect of vitamin D supplementation on all-cause mortality; 8 
trials provided vitamin D2 (dose range, 208–4500 IU/day), and 14 
trials provided vitamin D3 (dose range, 10–6000 IU/day). Vitamin D3 
supplementation significantly lowered mortality risk (relative risk, 
0.9), but vitamin D2 supplementation did not.

Comment

In this analysis, the observational data showed an inverse association 
between blood 25-hydroxyvitamin D levels and death, but reverse 
causality is possible (i.e., ill people having low vitamin D levels 
rather than low vitamin D levels causing illness). In randomized 
trials, vitamin D3 supplementation modestly lowered all-cause 
mortality risk; however, the optimal dose and duration of vitamin D3 
supplementation are unknown. Thus, widespread vitamin D 
supplementation should not be recommended.

Chowdhury R et al., BMJ 2014 
Apr 1; 348:g1903

Should We Supplement With Vitamin D

Two BMJ meta-analyses on vitamin D have found that evidence for 
benefit is narrow and that if there is a benefit, the form of 
supplementation has a bearing on its magnitude.

One, an “umbrella review” of meta-analyses and systematic reviews, 
found no “highly convincing” evidence linking circulating vitamin D 
levels with any of 137 outcomes, such as colorectal cancer or 
hypertension. It found a “probable” link for only three outcomes: 
birth weight, parathyroid hormone levels in dialysis patients, and 
dental caries in children.

The other meta-analysis found, in observational data, a salutary 
effect of increasing vitamin D levels on mortality. In randomized, 
controlled trials, the analysis found a significant mortality benefit 
from vitamin D3 supplements, but not from the D2 form.

Editorialists champion new trials focusing on risks as well as 
benefits of supplementation, and advise against measuring circulating 
vitamin D beyond bone-disease-related conditions.

BMJ article 1