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Randomized trial · measured the question itself

52-week trial in 15,804 older adults: vitamin D did not clearly change colds

Camargo and colleagues · Clinical infectious diseases : an official publication of the Infectious Diseases Society of America · 2024

Original title: Effect of Daily Vitamin D Supplementation on Risk of Upper Respiratory Infection in Older Adults: A Randomized Controlled Trial.

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What the study found

No difference

Vitamin D did not change the odds of a recent cold or upper respiratory infection (OR 0.96, 95% CI .86-1.06). In the 255 people with low levels (<12 ng/mL), OR was 0.60 (.28-1.30).

The study at a glance

Type of study
Randomized trial
Who or what was studied
15,804 people · Mostly healthy men aged 50+ and women aged 55+, average age 68
What was tested
Vitamin D3 2000 IU a day vs placebo, with a check at 1 year
What it measured
The question itself: colds, flu and other respiratory infections
Daily amount
2000 IU a day
How long
52 weeks
Trial registration
NCT01169259
Who has a stake
Company stake
Pharmavite supplied the vitamin D pills and supported the trial; some authors report ties to Pharmavite, Pfizer and Quest Diagnostics.
Journal
Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 2024
Source
PubMed record 38113446. 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: 15,804 people.
  • ✓Long: about 1 year.
  • ✓Measured the question itself: colds, flu and other respiratory infections.
  • –Company stake: Pharmavite supplied the vitamin D pills and supported the trial; some authors report ties to Pharmavite, Pfizer and Quest Diagnostics.
  • •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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