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Randomized trial · measured the question itself

Trial in 581 pregnant Danish women: high-dose vitamin D, less croup by age 3

Brustad and colleagues · The journal of allergy and clinical immunology. In practice · 2023

Original title: Fish Oil and Vitamin D Supplementations in Pregnancy Protect Against Childhood Croup.

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What the study found

Points to benefit

Croup before age 3: 32 of 295 children (11%) in the high-dose vitamin D group vs 51 of 286 (18%) in the standard-dose group (hazard ratio = 0.60; 95% CI, 0.38-0.93; P = .02).

The study at a glance

Type of study
Randomized trial
Who or what was studied
581 people · Pregnant women in Denmark and their children, followed to age 3
What was tested
High-dose vitamin D (2800 IU a day) vs standard dose (400 IU a day) from week 24 of pregnancy to 1 week after birth; also fish oil vs olive oil
What it measured
The question itself: colds, flu and other respiratory infections
Daily amount
2800 IU a day
Trial registration
NCT00798226, NCT00856947
Who has a stake
No disclosure in PubMed
No disclosure in PubMed.
Journal
The journal of allergy and clinical immunology. In practice, 2023
Source
PubMed record 36184023. 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.
  • ✓Large: 581 people.
  • ✓Measured the question itself: colds, flu and other respiratory infections.
  • •The PubMed record has no conflict-of-interest statement.
  • •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: 1 benefit, 8 no difference. This one found benefit. It differs from 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 reviewer corrected 1 field after reading the abstract. 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
Source check by a person
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