What the reviews found
Supplements for Colds & Immunity
4 where systematic reviews concluded a benefit, 1 with mixed findings, 2 where they concluded no effect. Every line quotes the review and links it, so you can read the sentence yourself.
Reviews found a benefit
Systematic reviews concluded these improve an outcome tied to colds & immunity, and none concluded no effect.
- Benefitimmune function (cd3+/cd4+ t cells, cd4/cd8 ratio)
“Supplementation with APS can improve treatment outcomes, enhance immune function, and demonstrate a high level of safety in malignant tumor patients” PMID 40208321
- Beta-Glucan1 review citedBenefitrespiratory infection symptoms
“yeast β-glucan reduced respiratory infection symptoms in healthy adults.” PMID 40516031
- Benefitimmune function(as Ganoderma lucidum)
“Supplementation with beta-(1 → 3,1 → 6)-d-glucans is well-tolerated, and health-promoting properties are manifested primarily through the potentiation of the immune system.” PMID 33876798
- Top-scored productThorne Zinc Bisglycinate 30 mg1 review cited96Benefitimmune system function
“The evidence supports the effectiveness of nutritional interventions in boosting the immune system, with particular relevance for vitamin D and zinc supplementation.” PMID 42256481
Mixed: a benefit on one measure, no effect on another
- Top-scored productThorne Vitamin C 1,000 mg1 review cited90No effectcommon cold incidence
“The failure of vitamin C supplementation to reduce the incidence of colds in the general population indicates that routine vitamin C supplementation is not justified” PMID 23440782
Benefitcommon cold duration“Regular supplementation trials have shown that vitamin C reduces the duration of colds, but this was not replicated in the few therapeutic trials that have been carried out.” PMID 23440782
No effectcommon cold incidence(as Ascorbic Acid)“The failure of vitamin C supplementation to reduce the incidence of colds in the general population indicates that routine vitamin C supplementation is not justified, yet vitamin C may be useful for people exposed to brief periods of severe physical exercise.” PMID 23440782
Reviews found no effect
Reviews studied these for an outcome tied to colds & immunity and concluded they made no difference.
- 1 review citedNo effectrespiratory infections
“Current evidence does not support the routine use of probiotic or synbiotic supplementation for the prevention of respiratory infections in children aged ≤24 months.” PMID 42451071
- No effectimmune system overstimulation
“there is no evidence that it overstimulates the immune system” PMID 33827515
Not enough to say
Reviews of Echinacea could not conclude either way on colds & immunity.
How this page is built
Each finding is the conclusion a set of systematic reviews reached on one outcome — whether an ingredient helped, made no difference, or could not be judged — with a sentence quoted from one review, checked to appear in its PubMed abstract. It records the direction, not the size, of an effect. Reviews run in populations such as people with cancer, pregnancy, surgery or children are left out, because applying them to a general reader would mislead. Evidence last refreshed September 2026. Abstracts courtesy of the U.S. National Library of Medicine (PubMed).
Other goals
Educational only. A review finding a benefit on average does not mean a supplement will help you, or that it is safe alongside your medication. If you are treated for colds & immunity, talk to your clinician before adding anything.