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 A vs placebo

Mortality: all causes ‐ smokers and asbestos workers · healthy people and healthy male physicians

Vitamin A leads to higher mortality: all causes ‐ smokers and asbestos workers compared with placebo (high certainty).

1 finding from 1 review

Drugs for preventing lung cancer in healthy people 2020 · Cochrane Headline outcomes only
RR 1.09 [1.05, 1.13]
2 studies · 32883 participants
High

Vitamin E + vitamin C 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

Vitamin A vs placebo or usual care

All‐cause mortality · children aged between 6 months and 5 years

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

1 finding from 1 review

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

Mortality due to LRTI · children aged between 6 months and 5 years

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

1 finding from 1 review

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

Mortality due to measles · children aged between 6 months and 5 years

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

1 finding from 1 review

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

Mortality due to diarrhoea · children aged between 6 months and 5 years

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

1 finding from 1 review

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 K antagonist (VKA) prophylaxis vs no prophylaxis

All‐cause mortality · ambulatory people with cancer without venous thromboembolism receiving systemic therapy

Vitamin K antagonist (VKA) prophylaxis showed no clear difference in mortality compared with no prophylaxis (moderate certainty).

1 finding from 1 review

Oral anticoagulation in people with cancer who have no therapeutic or prophylactic indication for anticoagulation 2021 · Cochrane Headline outcomes only
RR 0.95 [0.87, 1.03]
5 studies · 1281 participants
Moderate

Vitamin C vs placebo

All‐cause mortality Physicians · middle‐aged US male physicians

It is very uncertain whether vitamin C supplementation changes all‐cause mortality Physicians compared with placebo (very low certainty).

1 finding from 1 review

Vitamin C supplementation for the primary prevention of cardiovascular disease 2017 · Cochrane Headline outcomes only
HR 1.07 [0.97, 1.18]
1 study · 14641 participants
Very low

Staple foods fortified with vitamin A vs same unfortified staple foods

All‐cause mortality · general population over 2 years of age

The review found no eligible studies for this question.

1 finding from 1 review

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

Vitamin A supplementation (200,000 to 400,000 IU) vs placebo or no treatment

Change in Infant Mortality Rate per 1000 live births1 · women in the postpartum period

Vitamin A supplementation (200,000 to 400,000 IU) showed no clear difference in infant mortality compared with placebo or no treatment (low certainty).

1 finding from 1 review

Vitamin A supplementation for postpartum women 2016 · Cochrane Headline outcomes only
RR 1.08 [0.77, 1.52]
5 studies · 6090 participants
Low

Vitamin C vs placebo

Cardiovascular mortality Physicians · middle‐aged US male physicians

It is very uncertain whether vitamin C supplementation changes cardiovascular mortality Physicians compared with placebo (very low certainty).

1 finding from 1 review

Vitamin C supplementation for the primary prevention of cardiovascular disease 2017 · Cochrane Headline outcomes only
HR 1.02 [0.85, 1.22]
1 study · 14641 participants
Very low

Vitamin A supplementation (200,000 to 400,000 IU) vs placebo or no treatment

Maternal death · women in the postpartum period

Vitamin A supplementation (200,000 to 400,000 IU) showed no clear difference in maternal mortality compared with placebo or no treatment (moderate certainty).

1 finding from 1 review

Vitamin A supplementation for postpartum women 2016 · Cochrane Headline outcomes only
HR 1.01 [0.44, 2.21]
1 study · 8577 participants
Moderate

Staple food fortified with vitamin A plus other micronutrients vs no intervention

All‐cause mortality · general population over 2 years of age

The review found no eligible studies for this question.

1 finding from 1 review

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

Staple food fortified with vitamin A plus other micronutrients vs same unfortified staple foods

All‐cause mortality · general population over 2 years of age

The review found no eligible studies for this question.

1 finding from 1 review

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

Vitamin K antagonists vs placebo or no thromboprophylaxis

1‐year overall mortality · ambulatory cancer patients receiving chemotherapy

The review found no eligible studies for this question.

1 finding from 1 review

Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy 2020 · Cochrane Headline outcomes only
no estimate extracted
Studies not reported
No studies found

Vitamin K antagonists vs active control

1‐year overall mortality · ambulatory cancer patients receiving chemotherapy

The review found no eligible studies for this question.

1 finding from 1 review

Primary prophylaxis for venous thromboembolism in ambulatory cancer patients receiving chemotherapy 2020 · Cochrane Headline outcomes only
no estimate extracted
Studies not reported
No studies found

Vitamin K antagonists vs low molecular weight heparin

All‐cause mortality · ambulatory patients with multiple myeloma receiving immunomodulatory agents

It is very uncertain whether vitamin K antagonist (VKA) changes all‐cause mortality compared with low molecular weight heparin (LMWH) (very low certainty).

2 findings from 1 review

Antithrombotic therapy for ambulatory patients with multiple myeloma receiving immunomodulatory agents 2021 · Cochrane Headline outcomes only
RR 0.33 [0.01, 8.1]
1 study · 439 participants
Very low
Antithrombotic therapy for ambulatory patients with multiple myeloma receiving immunomodulatory agents 2021 · Cochrane Headline outcomes only
RR 2 [0.18, 21.9]
1 study · 440 participants
Very low

Neonatal vitamin A supplementation vs control

Neonatal mortality · mortality and morbidity in term neonates

Neonatal vitamin A supplementation showed no clear difference in all‐cause neonatal mortality: risk ratios based on cumulative risk… compared with control (high certainty).

1 finding from 1 review

Neonatal vitamin A supplementation for the prevention of mortality and morbidity in term neonates in low and middle… 2017 · Cochrane Headline outcomes only
RR 0.99 [0.9, 1.08]
5 studies · 126242 participants
High

Neonatal vitamin A supplementation vs control

Infant Mortality at 6 Months · mortality and morbidity in term neonates

Neonatal vitamin A supplementation showed no clear difference in all‐cause infant mortality at 6 months: risk ratios based on… compared with control (high certainty).

1 finding from 1 review

Neonatal vitamin A supplementation for the prevention of mortality and morbidity in term neonates in low and middle… 2017 · Cochrane Headline outcomes only
RR 0.98 [0.89, 1.07]
11 studies · 154634 participants
High

Neonatal vitamin A supplementation vs control

All‐cause infant mortality at 6 months: risk ratios based on cumulative risk (%, adjusted for clustering) ‐ term infants · mortality and morbidity in term neonates

It is very uncertain whether neonatal vitamin A supplementation changes all‐cause infant mortality at 6 months: risk ratios based on… compared with control (very low certainty).

1 finding from 1 review

Neonatal vitamin A supplementation for the prevention of mortality and morbidity in term neonates in low and middle… 2017 · Cochrane Headline outcomes only
RR 0.8 [0.54, 1.18]
3 studies · 22721 participants
Very low