Findings

What do systematic reviews say?

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Evidence found and GRADE certainty

1,126 questions · 1,225 findings · 111 reviews

No studies found 235 · 19.2%GRADE not reported 260 · 21.2%Very low 207 · 16.9%Low 271 · 22.1%Moderate 177 · 14.4%High 75 · 6.1%

Vitamin A vs placebo

Incidence of acute URTIs during the study period (the number of acute URTIs over a period of time) · children up to the age of 7 at risk of upper respiratory tract infection

Summary of findings table ‐ Vitamin A supplements showed no clear difference in incidence of acute URTIs during the study period (the number of… compared with placebo (low certainty).

1 finding from 1 review

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

Adverse effects on women: abdominal cramps · women in the postpartum period

Vitamin A supplementation (200,000 to 400,000 IU) showed no clear difference in maternal adverse effects after administration: abdominal pain compared with placebo or no treatment (low certainty).

1 finding from 1 review

Multivitamin vs placebo

Average mouth pain during RAS episodes · Participants with a previous or current history of recurrent aphthous stomatitis (RAS), diagnosed on history and clinical examination;…

Daily multivitamin showed no clear difference in average mouth pain during RAS episodes compared with placebo; GRADE not reported.

1 finding from 1 review

Multivitamin vs placebo

Average number of new lesions per week · Participants with a previous or current history of recurrent aphthous stomatitis (RAS), diagnosed on history and clinical examination;…

Daily multivitamin showed no clear difference in mean number of new lesions compared with placebo; GRADE not reported.

1 finding from 1 review