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 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

Higher circulating 25-hydroxyvitamin D (25(OH)D) concentration vs Lower circulating 25-hydroxyvitamin D (25(OH)D) concentration

All cause mortality · people with chronic kidney disease (predialysis (GFR 15 to 60 mL/min/1.73 m²), HD, PD, transplant recipients)

Meta-analysis of observational studies (higher vs lower 25(OH)D) for All cause mortality, Patients with chronic kidney disease: RR 0.86 (95% CI 0.81 to 0.92), statistically significant. Umbrella review outcome-level evidence grade: No conclusion.

1 finding from 1 review

Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational… 2014 All outcomes
Patients with chronic kidney disease
RR 0.86 [0.81, 0.92]
10 studies · 6853 participants
GRADE not reported

Higher circulating 25-hydroxyvitamin D (25(OH)D) concentration vs Lower circulating 25-hydroxyvitamin D (25(OH)D) concentration

All cause mortality · Adults (general population)

Meta-analysis of observational studies (higher vs lower 25(OH)D) for All cause mortality: HR 0.72 (95% CI 0.66 to 0.78), statistically significant. Umbrella review outcome-level evidence grade: No conclusion.

1 finding from 1 review

Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational… 2014 All outcomes
HR 0.72 [0.66, 0.78]
18 studies · 77155 participants
GRADE not reported

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 D compounds (supplementation) vs placebo or control

All‐cause mortality · Adults with chronic kidney disease not requiring dialysis

Meta-analysis of randomised trials of vitamin D supplementation for Mortality: RR 1.40 (95% CI 0.38 to 5.15), not statistically significant. Umbrella review outcome-level evidence grade: No conclusion.

1 finding from 1 review

Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational… 2014 All outcomes
RR 1.40 [0.38, 5.15]
4 studies · 381 participants
GRADE not reported

Vitamin D compounds (supplementation) vs placebo or control

All‐cause mortality · Adults with chronic kidney disease requiring dialysis

Meta-analysis of randomised trials of vitamin D supplementation for Mortality: RR 1.34 (95% CI 0.34 to 5.24), not statistically significant. Umbrella review outcome-level evidence grade: No conclusion.

1 finding from 1 review

Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational… 2014 All outcomes
RR 1.34 [0.34, 5.24]
5 studies · 477 participants
GRADE not reported

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

Higher circulating 25-hydroxyvitamin D (25(OH)D) concentration vs Lower circulating 25-hydroxyvitamin D (25(OH)D) concentration

Cardiovascular mortality · Adults (general population)

Meta-analysis of observational studies (higher vs lower 25(OH)D) for Cardiovascular disease mortality: RR 0.55 (95% CI 0.36 to 0.85), statistically significant. Umbrella review outcome-level evidence grade: No conclusion.

1 finding from 1 review

Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational… 2014 All outcomes
RR 0.55 [0.36, 0.85]
5 studies · 24387 participants
GRADE not reported

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 D plus calcium vs calcium

All‐cause mortality

The review found no eligible studies for this question.

1 finding from 1 review

Vitamin D, calcium or a combination of vitamin D and calcium for the treatment of nutritional rickets in children 2020 · Cochrane Headline outcomes only
no estimate extracted
Studies not reported
No studies found

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 D vs placebo or control

Mortality (all cause) · Adults (general population)

Meta-analysis of randomised trials of vitamin D supplementation for Mortality (all cause) (Vitamin D2, general population): RR 1.04 (95% CI 0.97 to 1.11), not statistically significant. Umbrella review outcome-level evidence grade: No conclusion.

2 findings from 1 review

Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational… 2014 All outcomes
Vitamin D2, general population
RR 1.04 [0.97, 1.11]
8 studies · 17079 participants
GRADE not reported
Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational… 2014 All outcomes
Vitamin D3, general population
RR 0.91 [0.82, 1.02]
9 studies · 12824 participants
GRADE not reported