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Randomized trial · measured the question itself

6-month trial in 303 Chilean children: vitamin D did not clearly change respiratory infections

Reyes and colleagues · The Journal of pediatrics · 2024

Original title: Weekly Vitamin D Supplementation to Prevent Acute Respiratory Infections in Young Children at Different Latitudes: A Randomized Controlled Trial.

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What the study found

No difference

No group differences in number of respiratory infections (P = .85) or infection hospital stays (P = .20). Blood vitamin D rose with dose; 64% completed the study.

The study at a glance

Type of study
Randomized trial
Who or what was studied
303 people · Chilean children aged 1.5 to 3.5 years in three cities
What was tested
Vitamin D3 at 5600 or 11,200 IU a week vs placebo for 6 months
What it measured
The question itself: colds, flu and other respiratory infections
Daily amount
11200 IU/week
How long
26 weeks
Trial registration
NCT02046577
Who has a stake
No stake declared
No conflicts of interest declared; funded by a national Chilean health research fund.
Journal
The Journal of pediatrics, 2024
Source
PubMed record 39181322. This page is based on the abstract only.

How much this study counts

  • ✓Randomized: people were put into groups by chance, so the groups start out alike.
  • ✓Compared with a placebo, a dummy treatment.
  • ✓Large: 303 people.
  • •Lasted 26 weeks.
  • ✓Measured the question itself: colds, flu and other respiratory infections.
  • ✓No competing interests declared.
  • •Summarized from the PubMed abstract only. The full paper may hold details the abstract leaves out.

✓ Strength– Limit• Note

These points come from fixed rules about the type of study, its size and length, what it measured, and who has a stake. Every study on Digestery gets the same rules.

Where this study sits

Each dot is one on-topic paper on this question. Steps near the top answer the question more directly.

↑ Stronger evidence

  1. Trials in people: colds, flu and chest infections

    10

    2 benefit, 8 no difference

    ↑ This study is the ringed dot

  2. Trials in people: other measures

    5

    1 benefit, 1 mixed, 2 no difference, 1 harm

  3. Trials in people: lab tests or safety

    1

    1 no difference

  4. Population studies

    1

    1 no difference

  5. Blood levels and genes

    4

    3 benefit, 1 no difference

↓ Weaker evidence

  • Points to benefit
  • Mixed
  • No difference
  • No direction
  • Points to harm

How it fits with the other research

The short answer to “Does vitamin D prevent colds and infections?”

Not clearly; any effect looks small.

Confidence: low. Based on 33 on-topic papers.

Read the full answer

Of the other 9 papers on the same step: 2 benefit, 7 no difference. This one found no difference. It agrees with most of them.

Other papers on the same step

See all 33 studies on this question

How this page was made

Label

First read of the abstract
Claude Sonnet
Independent second read
Claude Haiku
Differences settled
The two reads agreed on every checked field. Claude Opus 5.5.
Headline
Claude Sonnet, from the checked study record. A script checked its numbers and wording.
Numbers
Checked against the abstract by a script
“How much this study counts”
Fixed rules, the same for every study
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