What do systematic reviews say?

Vitamin D vs placebo

• Micronutrient supplementation in adults with HIV infection 2017 · Cochrane Headline outcomes only
  no estimate extracted
  4 studies · 299 participants
  Moderate

Vitamin A plus iron plus folate vs iron plus folate

Vitamin A plus iron plus folate showed no clear difference in total fetal loss (including miscarriages or combined miscarriages… compared with iron plus folate (low certainty).

• Vitamin supplementation for preventing miscarriage 2016 · Cochrane Headline outcomes only
  RR 1.01 [0.61, 1.66]
  3 studies · 1640 participants
  Low

Vitamin A plus iron plus folate vs iron plus folate

Vitamin A plus iron plus folate showed no clear difference in early or late miscarriage ‐ Vitamin A + iron + folate versus iron +… compared with iron plus folate (low certainty).

• Vitamin supplementation for preventing miscarriage 2016 · Cochrane Headline outcomes only
  RR 0.86 [0.46, 1.62]
  2 studies · 1397 participants
  Low

Vitamin A plus iron plus folate vs iron plus folate

Vitamin A plus iron plus folate showed no clear difference in stillbirth ‐ Vitamin A + iron + folate versus iron + folate compared with iron plus folate (low certainty).

• Vitamin supplementation for preventing miscarriage 2016 · Cochrane Headline outcomes only
  RR 1.29 [0.57, 2.91]
  3 studies · 1640 participants
  Low

Neonatal vitamin A supplementation vs control

Neonatal vitamin A supplementation showed no clear difference in vitamin A deficiency (serum retinol < 0.70 micromol/L) at 6 weeks of… compared with control (high certainty).

• Neonatal vitamin A supplementation for the prevention of mortality and morbidity in term neonates in low and middle… 2017 · Cochrane Headline outcomes only
  RR 0.94 [0.75, 1.19]
  1 study · 612 participants
  High
• Neonatal vitamin A supplementation for the prevention of mortality and morbidity in term neonates in low and middle… 2017 · Cochrane Headline outcomes only
  RR 1.02 [0.64, 1.62]
  1 study · 369 participants
  High

Multivitamin plus iron plus folate vs iron plus folate

Multivitamin plus iron plus folate showed no clear difference in early or late miscarriage ‐ Multivitamin + iron + folic acid versus… compared with iron plus folate (moderate certainty).

• Vitamin supplementation for preventing miscarriage 2016 · Cochrane Headline outcomes only
  RR 0.98 [0.94, 1.03]
  10 studies · 94948 participants
  Moderate

Multivitamin plus iron plus folate vs iron plus folate

Multivitamin plus iron plus folate leads to lower stillbirth ‐ Multivitamin + iron + folic acid versus iron + folic acid compared with iron plus folate (high certainty).

• Vitamin supplementation for preventing miscarriage 2016 · Cochrane Headline outcomes only
  RR 0.92 [0.85, 0.99]
  10 studies · 79851 participants
  High

Multivitamin plus iron plus folate vs iron plus folate

Multivitamin plus iron plus folate showed no clear difference in total fetal loss (including miscarriages or combined miscarriages… compared with iron plus folate (high certainty).

• Vitamin supplementation for preventing miscarriage 2016 · Cochrane Headline outcomes only
  RR 0.96 [0.93, 1]
  10 studies · 94948 participants
  High

Staple foods fortified with vitamin A vs same unfortified staple foods

It is very uncertain whether staple foods fortified with vitamin A changes subclinical vitamin A deficiency (serum/plasma retinol 70 μmol/L or… compared with same unfortified staple foods (very low certainty).

• Fortification of staple foods with vitamin A for vitamin A deficiency 2019 · Cochrane Headline outcomes only
  RR 0.45 [0.19, 1.05]
  2 studies · 993 participants
  Very low

Staple foods fortified with vitamin A vs same unfortified staple foods

It is very uncertain whether staple foods fortified with vitamin A changes clinical vitamin A deficiency (defined as night blindness) compared with same unfortified staple foods (very low certainty).

• Fortification of staple foods with vitamin A for vitamin A deficiency 2019 · Cochrane Headline outcomes only
  RR 0.11 [0.01, 1.98]
  1 study · 581 participants
  Very low

Staple foods fortified with vitamin A vs same unfortified staple foods

The review found no eligible studies for this question.

• Fortification of staple foods with vitamin A for vitamin A deficiency 2019 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Summary of findings: fat‐soluble vitamin E vs control

The review found no eligible studies for this question.

• Vitamin E supplementation in people with cystic fibrosis 2020 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Summary of findings: fat‐soluble vitamin E vs control

The review found no eligible studies for this question.

• Vitamin E supplementation in people with cystic fibrosis 2020 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Summary of findings: fat‐soluble vitamin E vs control

The review found no eligible studies for this question.

• Vitamin E supplementation in people with cystic fibrosis 2020 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Summary of findings: fat‐soluble vitamin E vs control

• Vitamin E supplementation in people with cystic fibrosis 2020 · Cochrane Headline outcomes only
  no estimate extracted
  6 participants
  GRADE not reported

Vitamin D plus calcium vs placebo or control

Vitamin D [D2, D3 or 25(OH)D] plus calcium showed no clear difference in persons with hypercalcaemia ‐ Vitamin D (D2, D3 or 25(OH)D) plus… compared with control or placebo (low certainty).

• Vitamin D and vitamin D analogues for preventing fractures in post‐menopausal women and older men 2014 · Cochrane Headline outcomes only
  RR 3.29 [0.37, 29.14]
  2 studies · 3853 participants
  Low

Vitamin D plus calcium vs placebo or control

Vitamin D [D2, D3 or 25(OH)D] plus calcium leads to higher persons with renal disease (calculi or insufficiency) ‐ Vitamin D… compared with control or placebo (high certainty).

• Vitamin D and vitamin D analogues for preventing fractures in post‐menopausal women and older men 2014 · Cochrane Headline outcomes only
  RR 1.17 [1.03, 1.34]
  2 studies · 39552 participants
  High

Vitamin D plus calcium vs placebo or control

Vitamin D [D2, D3 or 25(OH)D] plus calcium showed no clear difference in deaths ‐ Vitamin D (D2, D3, 25(OH)D) plus calcium (1 year estimate) compared with control or placebo (high certainty).

• Vitamin D and vitamin D analogues for preventing fractures in post‐menopausal women and older men 2014 · Cochrane Headline outcomes only
  RR 0.94 [0.87, 1.02]
  6 studies · 46794 participants
  High

Summary of findings: water‐soluble vitamin E vs control

The review found no eligible studies for this question.

• Vitamin E supplementation in people with cystic fibrosis 2020 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Summary of findings: water‐soluble vitamin E vs control

Summary of findings: water‐soluble vitamin E may leads to higher vitamin E levels in serum: umol/L compared with control (low certainty).

• Vitamin E supplementation in people with cystic fibrosis 2020 · Cochrane Headline outcomes only
  MD 19.74 [13.48, 26]
  1 study · 45 participants
  Low