Findings

What do systematic reviews say?

87 questions · 90 findings · 34 reviews

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No studies found 18 · 20%GRADE not reported 11 · 12.2%Very low 12 · 13.3%Low 20 · 22.2%Moderate 14 · 15.6%High 15 · 16.7%

Vitamin D plus calcium vs placebo

Mortality: all cancers · relatively healthy postmenopausal women

Vitamin D plus calcium showed no clear difference in mortality: all cancers compared with placebo (moderate certainty).

1 finding from 1 review

Drugs for preventing lung cancer in healthy people 2020 · Cochrane Headline outcomes only
RR 0.91 [0.78, 1.05]
1 study · 34670 participants
Moderate

Intervention not reported

Cancer mortality in trials using vitamin D3 (cholecalciferol) ( · adults

The intervention probably leads to lower cancer mortality in trials using vitamin D3 (cholecalciferol) ( (moderate certainty).

1 finding from 1 review

Vitamin D supplementation for prevention of mortality in adults 2014 · Cochrane Headline outcomes only
RR 0.88 [0.78, 0.98]
4 studies · 44492 participants
Moderate

Intervention not reported

All‐cause mortality in trials using vitamin D3 (cholecalciferol) ( · adults

The intervention probably leads to lower all‐cause mortality in trials using vitamin D3 (cholecalciferol) ( (moderate certainty).

1 finding from 1 review

Vitamin D supplementation for prevention of mortality in adults 2014 · Cochrane Headline outcomes only
RR 0.94 [0.91, 0.98]
38 studies · 75927 participants
Moderate

Intervention not reported

Cardiovascular mortality in trials using vitamin D3 (cholecalciferol) ( · adults

The intervention showed no clear difference in cardiovascular mortality in trials using vitamin D3… (low certainty).

1 finding from 1 review

Vitamin D supplementation for prevention of mortality in adults 2014 · Cochrane Headline outcomes only
RR 0.98 [0.9, 1.07]
10 studies · 47267 participants
Low

Vitamin A vs placebo

All‐cause mortality · adults with HIV infection

1 finding from 1 review

Micronutrient supplementation in adults with HIV infection 2017 · Cochrane Headline outcomes only
no estimate extracted
0 studies · 0 participants
GRADE not reported

Vitamin C vs placebo

Mortality (pneumonia-associated) · school‐aged children (6 to 15 years) and marine corps recruits (mean age 18.5 years)

The review found no eligible studies for this question.

1 finding from 1 review

Vitamin C supplementation for prevention and treatment of pneumonia 2021 · Cochrane Headline outcomes only
no estimate extracted
Studies not reported
No studies found

Vitamin C vs placebo

Mortality (pneumonia-associated) · children under 5 years of age

The review found no eligible studies for this question.

1 finding from 1 review

Vitamin C supplementation for prevention and treatment of pneumonia 2021 · Cochrane Headline outcomes only
no estimate extracted
Studies not reported
No studies found

B vitamins vs placebo

Mortality ‐ not reported · MCI

The review found no eligible studies for this question.

1 finding from 1 review

Vitamin and mineral supplementation for preventing dementia or delaying cognitive decline in people with mild… 2018 · Cochrane Headline outcomes only
no estimate extracted
Studies not reported
No studies found

Higher dose vitamin K vs lower dose vitamin K

Mortality (all infants): 0.2 mg IM versus 0.5 mg IM · preterm infants

Higher dose vitamin K showed no clear difference in mortality (all infants): 0.2 mg IM versus 0.5 mg IM compared with lower dose vitamin K (low certainty).

1 finding from 1 review

Prophylactic vitamin K for the prevention of vitamin K deficiency bleeding in preterm neonates 2018 · Cochrane Headline outcomes only
RR 2.13 [0.6, 7.51]
1 study · 65 participants
Low

Intramuscular vitamin K vs intravenous vitamin K

Mortality (all infants): 0.2 mg IV versus 0.2 mg IM · preterm infants

Intramuscular vitamin K showed no clear difference in mortality (all infants): 0.2 mg IV versus 0.2 mg IM compared with intravenous vitamin K (low certainty).

1 finding from 1 review

Prophylactic vitamin K for the prevention of vitamin K deficiency bleeding in preterm neonates 2018 · Cochrane Headline outcomes only
RR 1.32 [0.56, 3.14]
1 study · 67 participants
Low

Intramuscular vitamin K vs intravenous vitamin K

Mortality (all infants): 0.2 mg IV versus 0.5 mg IM · preterm infants

Intramuscular vitamin K showed no clear difference in mortality (all infants): 0.2 mg IV versus 0.5 mg IM compared with intravenous vitamin K (low certainty).

1 finding from 1 review

Prophylactic vitamin K for the prevention of vitamin K deficiency bleeding in preterm neonates 2018 · Cochrane Headline outcomes only
RR 2.82 [0.84, 9.46]
1 study · 64 participants
Low

Vitamin E vs placebo

Mortality: all causes · healthy people

Vitamin E showed no clear difference in mortality: all causes compared with placebo (high certainty).

1 finding from 1 review

Drugs for preventing lung cancer in healthy people 2020 · Cochrane Headline outcomes only
RR 1.03 [0.99, 1.07]
3 studies · 69090 participants
High

Vitamin C vs placebo

Mortality: all cancers · healthy male physicians, period: 1997 to 2007 and female health professionals, period: 1998 to 2005

Vitamin C showed no clear difference in mortality: all cancers compared with placebo (high certainty).

1 finding from 1 review

Drugs for preventing lung cancer in healthy people 2020 · Cochrane Headline outcomes only
RR 1.11 [0.93, 1.34]
2 studies · 14953 participants
High

Vitamin A vs placebo

Mortality: lung cancer · healthy people and healthy male physicians

Vitamin A showed no clear difference in mortality: lung cancer compared with placebo (high certainty).

1 finding from 1 review

Drugs for preventing lung cancer in healthy people 2020 · Cochrane Headline outcomes only
RR 1.06 [0.81, 1.38]
3 studies · 190118 participants
High

Vitamin E vs placebo

Mortality: lung cancer · healthy people

Vitamin E showed no clear difference in mortality: lung cancer compared with placebo (high certainty).

1 finding from 1 review

Drugs for preventing lung cancer in healthy people 2020 · Cochrane Headline outcomes only
RR 0.96 [0.77, 1.18]
2 studies · 29214 participants
High

Vitamin E vs placebo

Mortality: all cancers · healthy people

Vitamin E showed no clear difference in mortality: all cancers compared with placebo (high certainty).

1 finding from 1 review

Drugs for preventing lung cancer in healthy people 2020 · Cochrane Headline outcomes only
RR 1.11 [0.99, 1.24]
2 studies · 54517 participants
High

Vitamin A vs placebo

Mortality: all cancers · healthy people and healthy male physicians

Vitamin A showed no clear difference in mortality: all cancers compared with placebo (high certainty).

1 finding from 1 review

Drugs for preventing lung cancer in healthy people 2020 · Cochrane Headline outcomes only
RR 1.02 [0.88, 1.77]
1 study · 22071 participants
High

Vitamin A vs placebo or no treatment

Maternal death · pregnant women

Vitamin A alone showed no clear difference in maternal mortality compared with placebo or no treatment (high certainty).

1 finding from 1 review

Vitamin A supplementation during pregnancy for maternal and newborn outcomes 2015 · Cochrane Headline outcomes only
RR 0.88 [0.65, 1.2]
4 studies · 154039 participants
High

Vitamin A vs placebo or no treatment

Perinatal mortality · pregnant women

Vitamin A alone showed no clear difference in perinatal mortality compared with placebo or no treatment (high certainty).

1 finding from 1 review

Vitamin A supplementation during pregnancy for maternal and newborn outcomes 2015 · Cochrane Headline outcomes only
RR 1.01 [0.95, 1.07]
1 study · 76176 participants
High

Vitamin C vs placebo

Mortality: lung cancer ‐ men · healthy male physicians, period: 1997 to 2007 and female health professionals, period: 1998 to 2005

Vitamin C showed no clear difference in mortality: lung cancer ‐ men compared with placebo (high certainty).

1 finding from 1 review

Drugs for preventing lung cancer in healthy people 2020 · Cochrane Headline outcomes only
RR 0.81 [0.53, 1.23]
1 study · 7326 participants
High