What do systematic reviews say?

Vitamin E + vitamin C vs placebo

Vitamin C and vitamin E showed no clear difference in stillbirth compared with placebo (moderate certainty).

• Vitamin supplementation for preventing miscarriage 2016 · Cochrane Headline outcomes only
  RR 1.31 [0.97, 1.76]
  7 studies · 21442 participants
  Moderate

SoF vitamin E vs placebo

• Non‐hormonal interventions for hot flushes in women with a history of breast cancer 2010 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 104 participants
  High

SoF vitamin E vs placebo

• Non‐hormonal interventions for hot flushes in women with a history of breast cancer 2010 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 104 participants
  High

Vitamin A vs placebo or usual care

Vitamin A supplementation leads to lower all‐cause mortality compared with placebo or usual care (high certainty).

• Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age 2022 · Cochrane Headline outcomes only
  RR 0.88 [0.83, 0.93]
  19 studies · 1202382 participants
  High

Vitamin A vs placebo or usual care

Vitamin A supplementation probably leads to higher vomiting compared with placebo or usual care (moderate certainty).

• Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age 2022 · Cochrane Headline outcomes only
  RR 1.97 [1.44, 2.69]
  4 studies · 10541 participants
  Moderate

Vitamin A vs placebo or usual care

Vitamin A supplementation leads to lower mortality due to diarrhoea compared with placebo or usual care (high certainty).

• Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age 2022 · Cochrane Headline outcomes only
  RR 0.88 [0.79, 0.98]
  9 studies · 1098538 participants
  High

Vitamin A vs placebo or usual care

Vitamin A supplementation showed no clear difference in mortality due to measles compared with placebo or usual care (low certainty).

• Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age 2022 · Cochrane Headline outcomes only
  RR 0.88 [0.69, 1.11]
  6 studies · 1088261 participants
  Low

Vitamin A vs placebo or usual care

Vitamin A supplementation showed no clear difference in mortality due to LRTI compared with placebo or usual care (low certainty).

• Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age 2022 · Cochrane Headline outcomes only
  RR 0.98 [0.86, 1.12]
  9 studies · 1098538 participants
  Low

Vitamin A vs placebo or usual care

Vitamin A supplementation may leads to lower diarrhoea incidence Mean episodes per child per year compared with placebo or usual care (low certainty).

• Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age 2022 · Cochrane Headline outcomes only
  RR 0.85 [0.82, 0.87]
  15 studies · 77946 participants
  Low

Vitamin A vs placebo or usual care

Vitamin A supplementation probably leads to lower measles incidence Mean episodes of measles per child per year compared with placebo or usual care (moderate certainty).

• Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age 2022 · Cochrane Headline outcomes only
  RR 0.5 [0.37, 0.67]
  6 studies · 19566 participants
  Moderate

Vitamin A vs placebo or usual care

Vitamin A supplementation showed no clear difference in LRTI incidence Mean episodes per child per year compared with placebo or usual care (low certainty).

• Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age 2022 · Cochrane Headline outcomes only
  RR 0.99 [0.92, 1.06]
  11 studies · 27540 participants
  Low

Vitamin A vs placebo or usual care

Vitamin A supplementation probably leads to lower bitot's spots incidence compared with placebo or usual care (moderate certainty).

• Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age 2022 · Cochrane Headline outcomes only
  RR 0.42 [0.33, 0.53]
  5 studies · 1063278 participants
  Moderate

Vitamin A vs placebo or usual care

Vitamin A supplementation probably leads to lower night blindness incidence compared with placebo or usual care (moderate certainty).

• Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age 2022 · Cochrane Headline outcomes only
  RR 0.32 [0.21, 0.5]
  2 studies · 22972 participants
  Moderate

Vitamin D vs placebo or no intervention

Vitamin D supplementation probably leads to lower pre‐eclampsia compared with placebo or no intervention (moderate certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.48 [0.3, 0.79]
  4 studies · 499 participants
  Moderate

Vitamin D vs placebo or no intervention

Vitamin D supplementation probably leads to lower gestational diabetes compared with placebo or no intervention (moderate certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.51 [0.27, 0.97]
  4 studies · 446 participants
  Moderate

Vitamin D vs placebo or no intervention

Vitamin D supplementation may leads to lower maternal adverse events: severe postpartum haemorrhage compared with placebo or no intervention (low certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.68 [0.51, 0.91]
  1 study · 1134 participants
  Low

Vitamin D vs placebo or no intervention

It is very uncertain whether vitamin D supplementation changes maternal adverse event: nephritic syndrome compared with placebo or no intervention (very low certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.17 [0.01, 4.06]
  1 study · 135 participants
  Very low

Vitamin D vs placebo or no intervention

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 1134 participants
  Low

Vitamin D vs placebo or no intervention

Vitamin D supplementation showed no clear difference in preterm birth (less than 37 weeks' gestation) compared with placebo or no intervention (low certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.66 [0.34, 1.3]
  7 studies · 1640 participants
  Low

Vitamin D vs placebo or no intervention

Vitamin D supplementation probably leads to lower low birthweight (less than 2500 g) compared with placebo or no intervention (moderate certainty).

• Vitamin D supplementation for women during pregnancy 2019 · Cochrane Headline outcomes only
  RR 0.55 [0.35, 0.87]
  5 studies · 697 participants
  Moderate