What do systematic reviews say?

Vitamin D vs placebo or control

Meta-analysis of randomised trials of vitamin D supplementation for Dental caries: RR 0.53 (95% CI 0.43 to 0.65), statistically significant. Umbrella review outcome-level evidence grade: Probable.

• Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational… 2014 All outcomes
  RR 0.53 [0.43, 0.65]
  38 studies · 1513 participants
  GRADE not reported

Vitamin D vs placebo or control

Meta-analysis of randomised trials of vitamin D supplementation for Insulin resistance (Diabetes): SMD 0.16 (95% CI -0.11 to 0.42), not statistically significant. Umbrella review outcome-level evidence grade: No conclusion.

• Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational… 2014 All outcomes

  Diabetes
  SMD 0.16 [-0.11, 0.42]
  5 studies
  GRADE not reported

Vitamin D 100,000 IU/month vs 12,000 IU/month

• Vitamin D supplementation for sickle cell disease 2020 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 62 participants
  Low

Vitamin D 100,000 IU/month vs 12,000 IU/month

Vitamin D 100,000 IU/month showed no clear difference in presence of pain compared with 12,000 IU/month (moderate certainty).

• Vitamin D supplementation for sickle cell disease 2020 · Cochrane Headline outcomes only
  RR 1 [0.62, 1.62]
  1 study · 62 participants
  Moderate

Vitamin D 100,000 IU/month vs 12,000 IU/month

• Vitamin D supplementation for sickle cell disease 2020 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 62 participants
  Moderate

Vitamin D 100,000 IU/month vs 12,000 IU/month

• Vitamin D supplementation for sickle cell disease 2020 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 62 participants
  Moderate

Vitamin D 100,000 IU/month vs 12,000 IU/month

The review found no eligible studies for this question.

• Vitamin D supplementation for sickle cell disease 2020 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Vitamin D 100,000 IU/month vs 12,000 IU/month

The review found no eligible studies for this question.

• Vitamin D supplementation for sickle cell disease 2020 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Low‐level laser therapy, wrist splint, and vitamin B6 vs placebo, wrist splint, and vitamin B6

• Low‐level laser therapy for carpal tunnel syndrome 2017 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 33 participants
  Very low

Low‐level laser therapy, wrist splint, and vitamin B6 vs placebo, wrist splint, and vitamin B6

The review found no eligible studies for this question.

• Low‐level laser therapy for carpal tunnel syndrome 2017 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Low‐level laser therapy, wrist splint, and vitamin B6 vs placebo, wrist splint, and vitamin B6

• Low‐level laser therapy for carpal tunnel syndrome 2017 · Cochrane Headline outcomes only
  no estimate extracted
  1 study · 33 participants
  Very low

Low‐level laser therapy, wrist splint, and vitamin B6 vs placebo, wrist splint, and vitamin B6

The review found no eligible studies for this question.

• Low‐level laser therapy for carpal tunnel syndrome 2017 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Low‐level laser therapy, wrist splint, and vitamin B6 vs placebo, wrist splint, and vitamin B6

The review found no eligible studies for this question.

• Low‐level laser therapy for carpal tunnel syndrome 2017 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Oral vitamin B vs no treatment

• Interventions for leg cramps in pregnancy 2020 · Cochrane Headline outcomes only
  no estimate extracted
  0 studies · 0 participants
  GRADE not reported

Vitamin A plus iron plus folate vs iron plus folate

The review found no eligible studies for this question.

• Vitamin supplementation for preventing miscarriage 2016 · Cochrane Headline outcomes only
  no estimate extracted
  Studies not reported
  No studies found

Any intermittent iron regimen (with or without other vitamins and minerals) vs daily regimen (with same vitamins and minerals)‐maternal outcomes

Any intermittent iron regimen (with or without other vitamins and… showed no clear difference in low birthweight (less than 2500 g) compared with daily regimen (with same vitamins and minerals)‐infant outcomes (low certainty).

• Intermittent oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.82 [0.55, 1.22]
  8 studies · 1898 participants
  Low

Any intermittent iron regimen (with or without other vitamins and minerals) vs daily regimen (with same vitamins and minerals)‐maternal outcomes

It is very uncertain whether any intermittent iron regimen (with or without other vitamins and… changes side effects (any reported throughout intervention period) compared with daily regimen (with same vitamins and minerals)‐maternal outcomes (very low certainty).

• Intermittent oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0.56 [0.37, 0.84]
  11 studies · 1777 participants
  Very low

Any intermittent iron regimen (with or without other vitamins and minerals) vs daily regimen (with same vitamins and minerals)‐maternal outcomes

• Intermittent oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  no estimate extracted
  6 studies · 1240 participants
  Very low

Any intermittent iron regimen (with or without other vitamins and minerals) vs daily regimen (with same vitamins and minerals)‐maternal outcomes

Any intermittent iron regimen (with or without other vitamins and… led to lower maternal clinical malaria or other infection in pregnancy compared with daily regimen (with same vitamins and minerals)‐maternal outcomes; GRADE not reported.

• Intermittent oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  RR 0 [0, 0]
  0 studies · 0 participants
  GRADE not reported

Any intermittent iron regimen (with or without other vitamins and minerals) vs daily regimen (with same vitamins and minerals)‐maternal outcomes

Any intermittent iron regimen (with or without other vitamins and… showed no clear difference in birthweight (g) compared with daily regimen (with same vitamins and minerals)‐infant outcomes (low certainty).

• Intermittent oral iron supplementation during pregnancy 2015 · Cochrane Headline outcomes only
  MD 5.13
  9 studies · 1939 participants
  Low