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The Human Effect Matrix looks at human studies to tell you what supplements affect Upper Respiratory Tract Infection Risk.
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| Grade | Level of Evidence [show legend] |
|---|---|
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Robust research conducted with repeated double-blind clinical trials |
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Multiple studies where at least two are double-blind and placebo controlled |
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Single double-blind study or multiple cohort studies |
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Uncontrolled or observational studies only |
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Level of Evidence
?
The amount of high quality evidence. The more
evidence, the more we can trust the results.
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Supplement |
Magnitude of effect
?
The direction and size of the supplement's impact on
each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
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Consistency of research results
?
Scientific research does not always agree. HIGH or
VERY HIGH means that most of the scientific research agrees.
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Notes |
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Minor
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High See all 14 studies |
The reduction in the rate of UPRTIs seen with echinacea as a daily supplement is highly effective in some instances, but subject to a high degree of variability. Overall, the evidence supports small-moderate efficacy, with the caveat that heterogeneity is moderate.
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Minor
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Very High See all 16 studies |
Studies overall support a modest-moderate reduction in the rate of upper respiratory tract infections overall, with greater reductions for those with low vitamin D levels. There is some evidence that daily or weekly supplementation of vitamin D is more effective than large bolus doses, and while suggestive of a benefit, it's unclear if large bolus doses themselves are meaningfully beneficial.
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- See all 25 studies |
When used as a prophylactic, vitamin C's effects are very inconsistent, and overall it doesn't seem to reliably reduce the risk of getting a common cold. It's possible that those undergoing extreme exercise (a known risk factor for developing colds) see a meaningful reduction in risk, however this is based on much less research and requires further study. It's unclear if other infectious diseases are affected by vitamin C supplementation.
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