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Randomized trial · measured the question itself

28-week trial in 408 adults with asthma: vitamin D did not clearly change colds

Denlinger and colleagues · American journal of respiratory and critical care medicine · 2016

Original title: Vitamin D Supplementation and the Risk of Colds in Patients with Asthma.

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What the study found

No difference

Cold severity score was no different: 62.0 on placebo vs 58.7 on vitamin D (P = 0.39). Cold rate did not differ (rate ratio, 1.2; 95% CI, 0.9-1.5). Among African Americans, colds were more frequent on vitamin D (RR, 1.7; 95% CI, 1.1-2.7).

The study at a glance

Type of study
Randomized trial
Who or what was studied
408 people · Adults with mild to moderate asthma and low vitamin D
What was tested
Vitamin D3 100,000 IU load then 4,000 IU a day vs placebo for 28 weeks
What it measured
The question itself: colds, flu and other respiratory infections
Daily amount
4000 IU a day
How long
28 weeks
Who has a stake
No disclosure in PubMed
No disclosure in PubMed; funded by NIH institutes.
Journal
American journal of respiratory and critical care medicine, 2016
Source
PubMed record 26540136. 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: 408 people.
  • •Lasted 28 weeks.
  • ✓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: 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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