Findings

What do systematic reviews say?

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Evidence found and GRADE certainty

780 questions · 834 findings · 76 reviews

No studies found 187 · 22.4%GRADE not reported 164 · 19.7%Very low 144 · 17.3%Low 172 · 20.6%Moderate 105 · 12.6%High 62 · 7.4%

Vitamin D deficiency (serum 25(OH)D < 50 nmol/L) vs Normal vitamin D level (serum 25(OH)D ≥ 50 nmol/L)

Dental caries · Children (mixed dentition; baseline about 8 years)

In children with mixed dentition, vitamin D deficiency was associated with an 8% higher caries risk (RR 1.08; ungraded).

1 finding from 1 review

Vitamin D + calcium + other vitamins and minerals vs calcium + other vitamins and minerals (but no vitamin D)

Gestational diabetes · pregnant women and their infants..

It is very uncertain whether vitamin D + calcium + other vitamins and minerals changes gestational diabetes compared with calcium + other vitamins and minerals (but no vitamin D) (very low certainty).

1 finding from 1 review

Vitamin D + calcium + other vitamins and minerals vs calcium + other vitamins and minerals (but no vitamin D)

Preterm birth · pregnant women and their infants..

Vitamin D + calcium + other vitamins and minerals showed no clear difference in preterm birth (less than 37 weeks' gestation) compared with calcium + other vitamins and minerals (but no vitamin D) (low certainty).

1 finding from 1 review

Vitamin D + calcium + other vitamins and minerals vs calcium + other vitamins and minerals (but no vitamin D)

Low birthweight · pregnant women and their infants..

Vitamin D + calcium + other vitamins and minerals showed no clear difference in low birthweight (less than 2500 g) compared with calcium + other vitamins and minerals (but no vitamin D) (low certainty).

1 finding from 1 review

Any‐treatment‐dose vitamin D (greater than 400 IU/day) vs supplemental‐dose vitamin D (less than 400 IU/day)

Withdrawals due to adverse events · people with inflammatory bowel disease

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

1 finding from 1 review

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

Maternal anaemia · pregnant women

It is very uncertain whether summary of findings table ‐ Vitamin B12 supplementation changes maternal anaemia compared with placebo/no vitamin B12 supplementation (very low certainty).

1 finding from 1 review

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

Low birthweight · pregnant women

Summary of findings table ‐ Vitamin B12 supplementation showed no clear difference in low birthweight (< 2500 g) compared with placebo/no vitamin B12 supplementation (low certainty).

1 finding from 1 review

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