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Length of Sickness

Length of sickness is the duration of which symptoms of a cold or infection persist, and reducing the duration of sickness is said to be a pro-immunity effect. Supplements may either be a daily supplement or taken on an as-needed basis.

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Human Effect Matrix

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The Human Effect Matrix looks at human studies to tell you what supplements affect Length of Sickness.

Full details on all Length of Sickness supplements are available to Examine Plus members.
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
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.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
grade-a - - See all 13 studies
Although early studies and an early meta-analysis suggested a benefit in the common cold, a more recent meta-analysis that using a higher threshold for bias risk for study inclusion didn't find a meaningful effect for upper respiratory tract infection in general (the common cold being the most common infection observed). It's unclear when echinacea may be most potent, or if certain doses, forms, and populations modify its effects, and a lack of new, well-conducted studies limits further analysis.
grade-b Minor Moderate See all 26 studies
The evidence suggests that a small (roughly half a day) reduction is found when vitamin C is taken consistently, even when not sick, but not if it's only started once already sick. For other infectious diseases, it's unclear if vitamin C helps.
grade-b Minor Very High See all 13 studies
Zinc lozenges, particularly over 75 mg per day (taken in divided doses roughly every 2 hours while awake), and particularly from zinc acetate, have evidence for a small-moderate reduction in the duration of common colds. While evidence points to high dose zinc acetate as the most effective, this is from comparisons between different studies, and as such, isn't as strong as head-to-head comparisons. More research is needed to confirm the most effective method of zinc lozenge use.

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