Findings

What do systematic reviews say?

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Evidence found and GRADE certainty

973 questions · 1,024 findings · 106 reviews

No studies found 235 · 22.9%GRADE not reported 59 · 5.8%Very low 207 · 20.2%Low 271 · 26.5%Moderate 177 · 17.3%High 75 · 7.3%

Summary of findings table ‐ Vitamin B12 supplementation vs no supplementation or placebo

Preterm birth · pregnant women

Summary of findings table ‐ Vitamin B12 supplementation showed no clear difference in preterm birth (< 37 weeks) compared with placebo/no vitamin B12 supplementation (low certainty).

1 finding from 1 review

High‐treatment‐dose vitamin D (greater than 1000 IU/day) vs low‐treatment‐dose vitamin D (400 IU/day to 1000 IU/day)

Clinical relapse · people with inflammatory bowel disease

High‐treatment‐dose vitamin D (greater than 1000 IU/day) showed no clear difference in clinical relapse at end of study (52 weeks) compared with low‐treatment‐dose vitamin D (400 IU/day to 1000 IU/day) (low certainty).

1 finding from 1 review

High‐treatment‐dose vitamin D (greater than 1000 IU/day) vs low‐treatment‐dose vitamin D (400 IU/day to 1000 IU/day)

Withdrawals due to adverse events · people with inflammatory bowel disease

It is very uncertain whether high‐treatment‐dose vitamin D (greater than 1000 IU/day) changes withdrawals due to adverse events compared with low‐treatment‐dose vitamin D (400 IU/day to 1000 IU/day) (very low certainty).

1 finding from 1 review