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Randomized trial · measured the question itself

26-week trial in 5,979 UK adults offered vitamin D: no clear fall in infections

Jolliffe and colleagues · BMJ (Clinical research ed.) · 2022

Original title: Effect of a test-and-treat approach to vitamin D supplementation on risk of all cause acute respiratory tract infection and covid-19: phase 3 randomised controlled trial (CORONAVIT).

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What the study found

No difference

At least one respiratory infection: 4.6% with no offer, 5.7% with lower dose (odds ratio 1.26, 95% CI 0.96 to 1.66) and 5.0% with higher dose (1.09, 0.82 to 1.46). COVID-19: 1.39 (0.98 to 1.97) and 1.13 (0.78 to 1.63).

The study at a glance

Type of study
Randomized trial
Who or what was studied
5,979 people · People aged 16 and over in the UK not taking vitamin D
What was tested
Offer of a blood test and 6 months of vitamin D (800 or 3200 IU a day) if low, vs no test and no vitamin D
What it measured
The question itself: colds, flu and other respiratory infections
Daily amount
3200 IU a day
How long
26 weeks
Trial registration
NCT04579640
Who has a stake
Company stake
Funded in part by Pharma Nord, DSM Nutritional Products, Thornton & Ross and others; lead authors report ties to vitamin D makers.
Journal
BMJ (Clinical research ed.), 2022
Source
PubMed record 36215226. 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: 5,979 people.
  • •Lasted 26 weeks.
  • ✓Measured the question itself: colds, flu and other respiratory infections.
  • –Company stake: Funded in part by Pharma Nord, DSM Nutritional Products, Thornton & Ross and others; lead authors report ties to vitamin D makers.
  • •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 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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