Common Cold
Supplements studied for common cold.
Overview
Common cold research here centers on Echinacea, Vitamin C, Zinc, Vitamin D, and Eleuthero-containing Kan Jang. Echinacea may modestly reduce cold incidence and duration in some trials, though product and regimen differences limit consistency.
High-dose Vitamin C may slightly shorten symptom severity and duration but does not reliably prevent infection. Zinc and Vitamin D are marked possibly effective in this database with multiple indexed trials. Kan Jang (eleuthero plus andrographis) started early may relieve symptoms within days in studied formulations. See the heatmap and evidence reviews below for product-specific outcomes.
Effect graph
Relevant supplements
Relevant supplements sorted by DEX Score.
| Zinc | ★★★★★ | Medium |
| Vitamin C | ★★★★★ | Medium |
| Eleuthero | ★★★★★ | Low |
| Garlic | ★★★★★ | Low |
| Panax Ginseng | ★★★★★ | Low |
| Green Tea | ★★★★★ | Low |
| Elderberry | ★★★★★ | Low |
| Echinacea | ★★★★★ | Very Low / None |
| Vitamin D | ★★★★★ | Very Low / None |
Studies
Find individual evidence reviews for supplements sorted by DEX Score.
9 supplements for and rated at least stars. All purchase bands. No minimum star filter.
Vitamin CView supplement →
Consider purchase·★★★★★
How we scored this▸
- Taking high doses of vitamin C might slightly shorten colds and reduce symptoms, but it does not stop people from catching colds.
- Studies show that taking 1 to 4 grams of vitamin C daily can reduce how bad cold symptoms get by about 13% and may shorten severe symptoms by one to one and a half days.
- It also helps reduce missed days from school or work.
- Vitamin C seems to work better for children and people who do a lot of physical exercise.
- Eating foods high in vitamin C does not change how often people get colds.
Browse 19 studies·2 meta-analyses
MetaVitamin C reduces the severity of common colds: a meta-analysis2023
A meta-analysis of 10 double-blind RCTs (≥1 g/day vitamin C) found vitamin C reduced common cold severity 15%, with greater benefit on severe symptoms.
- Effect
- Benefit
- Dose
- 1 g/day
- Population
- Children
MetaVitamin C for preventing and treating the common cold2013n=10,708
A Cochrane systematic review assessing vitamin C for both prevention and treatment of colds. Routine supplementation did not reduce incidence in the general population but consistently shortened duration and reduced severity of colds. Among individuals under heavy physical stress (e.g., marathon runners), incidence was significantly reduced. A meta-analysis found that doses of at least 200 mg Vitamin C per day reduced the odds of acquiring a cold, but only in people undergoing strenuous physical exercise. Taking vitamin C in the days leading up to a marathon halved the risk of acquiring a cold. Subgroup analysis in the above meta-analysis (24 entries including 10,708 participants) found that ongoing supplementation of vitamin C did not reduce the incidence of colds (RR 0.97, 95% CI 0.94 to 1.00). Analysis restricted to vitamin C doses ≥ 1 g/day (17 entries including 6661 participants) found no reduction in the risk of acquiring a cold (RR 0.98, 95% CI 0.95 to 1.01). Cold Severity Results (Ongoing Vitamin C Consumption, 31 comparisons, 9745 episodes): - In adults: Doses of ≥ 0.2 g/day vitamin C reduced common cold duration by 8% (3% to 12%). - In children: Doses of 1 to 2 g/day vitamin C reduced common cold duration by 18%; doses ≥ 0.2 g/day vitamin C reduced common cold duration by 14% (7% to 21%). - Stratified by gender: One study included in the meta-analysis found that vitamin C significantly reduced common cold duration in male adolescent swimmers (-47%) but not in female swimmers .
- Effect
- Benefit
- Dose
- 1 g/day
- Population
- Adults
- Participants
- 10,708
ObservationalIntake of vitamin C and zinc and risk of common cold: a cohort study2002
A cohort of 4,272 Spanish workers followed 1 year found vitamin C and zinc intake were not associated with common cold incidence.
- Effect
- No Benefit
- Duration
- 1 year
- Population
- Adults
- Ages
- 21–65
RCTMega-dose vitamin C in treatment of the common cold: a randomised controlled trial2001n=400
An RCT in 400 healthy adults found megadose vitamin C (1–3 g at cold onset) did not shorten cold duration or severity versus low-dose placebo over 18 months.
- Effect
- No Benefit
- Duration
- 18 months
- Dose
- 1 g/day
- Population
- Healthy adults
- Participants
- 400
Systematic reviewVitamin C for preventing and treating the common cold2000
A Cochrane review of 30 trials found regular high-dose vitamin C did not prevent colds but modestly reduced cold duration (~8% fewer symptom days).
- Effect
- Benefit
GuideCriteria and recommendations for vitamin C intake1999
A review proposed an RDA of 120 mg/day vitamin C based on nine criteria, with 5 daily fruit/vegetable servings providing ~200 mg.
- Effect
- Benefit
- Dose
- 100 mg/day
- Population
- General population
Controlled trialThe effectiveness of vitamin C in preventing and relieving the symptoms of virus-induced respiratory infections1999
A study of 715 students found hourly 1,000 mg vitamin C at cold onset reduced flu and cold symptoms 85% versus control over one winter.
- Effect
- Benefit
- Dose
- 1,000 mg vitamin C every hour for 6 h at onset
- Ages
- 18–32
RCTVitamin C supplementation and common cold symptoms: factors affecting the magnitude of the benefit1999
An analysis of 23 vitamin C cold trials found greater benefit in children than adults and at doses ≥2 g/day versus 1 g/day.
- Effect
- Benefit
- Dose
- 1 g/day
- Population
- Adults
MetaVitamin C intake and susceptibility to the common cold1997
A pooled analysis of six trials (>5,000 episodes) found vitamin C did not reduce cold incidence overall but halved incidence in British male schoolchildren (RR 0.70).
- Effect
- No Benefit
- Dose
- 1 g/day
RCTVitamin C supplementation and the common cold—was Linus Pauling right or wrong?1997
A review concluded Pauling was correct that vitamin C affects colds but overestimated benefit magnitude based largely on one Swiss skiing camp trial.
- Effect
- Benefit
- Dose
- 1 g/day
- Population
- Children
RCTVitamin C supplementation and common cold symptoms: problems with inaccurate reviews1996
A review argued three influential reviews misrepresented evidence that vitamin C alleviates common cold symptoms in placebo-controlled trials.
- Effect
- No Benefit
- Dose
- 1 g/day
RCTVitamin C, the placebo effect, and the common cold: a case study of how preconceptions influence the analysis of results1996
A reanalysis argued the placebo explanation for Karlowski's 6 g/day vitamin C cold trial was inconsistent with the data, supporting a real therapeutic effect.
- Dose
- 6 g/day
RCTDoes vitamin C alleviate the symptoms of the common cold?—a review of current evidence1994
A review of 21 placebo-controlled trials found vitamin C reduced cold duration and severity ~23% on average but clinical significance remained unclear.
- Effect
- Benefit
- Dose
- 1 g/day
Co-twin control studies: vitamin C and the common cold1982
A co-twin control study of vitamin C and the common cold; the abstract provided insufficient outcome detail for a definitive conclusion.
Controlled trialVitamin C and the common cold: using identical twins as controls1981
A double-blind trial in 95 identical twin pairs found vitamin C shortened average cold duration 19% over 100 days versus placebo.
- Effect
- Benefit
- Duration
- 100 days
The vitamin C controversy1980
An editorial on the vitamin C controversy; the abstract provided insufficient outcome detail for a definitive conclusion.
- Effect
- Benefit
Clinical trialAscorbic acid and the common cold: reviewing the evidence1979
A review concluded large vitamin C cold trials show only modest, inconsistent benefits likely reflecting placebo effects or minor physiologic changes.
- Effect
- No Benefit
Vitamin C and the common cold1979
A brief report on vitamin C and the common cold; the abstract provided insufficient outcome detail for a definitive conclusion.
RCTVitamin C prophylaxis in marine recruits1979
An RCT in 674 marine recruits found 2 g/day vitamin C for 8 weeks did not reduce cold incidence, supporting no prophylactic benefit.
- Effect
- No Benefit
- Duration
- 8 weeks
- Dose
- 2.0 g/day
ZincView supplement →
Consider purchase·★★★★★
How we scored this▸
- Zinc is possibly effective for Common cold.
Browse 14 studies·1 meta-analysis
RCTZinc acetate lozenges for the treatment of the common cold: a randomised controlled trial2020n=253
Among 87 adults who caught a cold, zinc acetate lozenges (13 mg elemental zinc, up to 6×/day for 5 days) did not improve recovery rate versus taste-matched placebo.
- Effect
- No Benefit
- Duration
- 5 days
- Dose
- 13 mg elemental zinc, 6×/day for 5 days
- Population
- Adults
- Participants
- 253
- Ages
- 18+
RCTZinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage2017n=575
A meta-analysis comparing clinical efficacy between zinc acetate and zinc gluconate lozenges and evaluating how zinc dosage influences cold symptom reduction. A meta-analysis of 7 studies including 575 participants with naturally acquired common colds found that the average common cold duration was 33% shorter (95% CI 21% to 45%) for the zinc acetate and zinc gluconate groups. In three trials that used zinc acetate, the average cold duration was shortened by 40% and by 28% in four trials that used zinc gluconate. The difference between elemental zinc at 80-92 mg/day and 192-207 mg/day doses was not significant. There is no evidence that high dose zinc lozenges are superior to doses of around 100 mg/day.
- Effect
- Benefit
- Dose
- 75 mg/day
- Population
- Adults
- Participants
- 575
The immune system and the impact of zinc during aging2009
A review of studies in older adults found that marginal zinc deficiency may worsen age-related immune dysregulation and that zinc supplementation can reduce inflammatory markers in elderly participants.
- Effect
- No Benefit
- Population
- Older adults
RCTDuration and severity of symptoms and levels of plasma interleukin-1 receptor antagonist, soluble tumor necrosis factor receptor, and adhesion molecules in patients with common cold treated with zinc acetate2008n=50
A clinical trial assessing how zinc acetate affects symptom duration and inflammatory cytokine levels in patients with the common cold. A study of 50 volunteers recruited within 24 hours of developing common cold symptoms found that zinc acetate (13.3 mg every 2-3 h when awake) reduced mean overall duration of cold (4.0 vs. 7.1 days placebo; P < 0.001), runny nose (3.0 vs. 4.5 days; P = 0.02) and cough (2.1 vs. 5.0 days, P < 0.0001) when compared to placebo.
- Effect
- Benefit
- Dose
- 13.3 mg
- Population
- Cancer patients
- Participants
- 50
Clinical trialZinc supplementation in the elderly reduces spontaneous inflammatory cytokine release and restores T cell functions2008n=19
In 19 healthy elderly adults, moderate zinc supplementation reduced spontaneous cytokine release, improved T-cell mitogenic responses, and lowered preactivated T-cell levels without suppressing immune function.
- Effect
- Benefit
- Population
- Older adults
- Participants
- 19
RCTZinc supplementation decreases incidence of infections in the elderly: effect of zinc on generation of cytokines and oxidative stress2007n=31
A randomized trial evaluating whether zinc supplementation lowers infection rates in older adults by modulating cytokine production and oxidative stress. A 12-month study of 49 healthy elderly subjects (55-87 yrs) found that zinc gluconate (45 mg elemental zinc per day) significantly reduced the incidence of infections, increased plasma zinc and reduced oxidative stress markers. When compared to a group of younger adults (n = 31, 18-54 yrs), older adults had significantly lower baseline plasma zinc, higher plasma oxidative stress markers and greater ex vivo generation of inflammatory cytokines and interleukin 10.
- Effect
- Benefit
- Duration
- 12 months
- Dose
- 45 mg elemental Zn/day
- Population
- Healthy adults
- Participants
- 31
- Ages
- 55–87
RCTDuration of symptoms and plasma cytokine levels in patients with the common cold treated with zinc acetate. A randomized, double-blind, placebo-controlled trial2000n=48
A randomized double-blind placebo-controlled trial assessing whether zinc acetate shortens duration of cold symptoms and alters cytokine profiles. A study of 48 participants recruited within 24 hours of developing cold symptoms found that 12.8 mg zinc acetate lozenges taken every 2-3 hours as long as they still had symptoms, reduced duration of cold symptoms (4.5 vs. 8.1 days), cough (3.1 [95% CI, 2.1 to 4.1] vs. 6.3 [4.9 to 7.7] days) and nasal discharge (4.1 [3.3 to 4.9] vs. 5.8 [4.3 to 7.3] days). Zinc significantly reduced severity of all symptoms (P < 0.002). There were no significant differences between cytokine levels in the zinc group and the placebo group (P > 0.2) but measurements were taken 3 days later in the placebo group, after cold symptoms had resolved. The mean change in soluble interleukin-1 receptor antagonist level was greater in the zinc group than the placebo group (-153.5 vs. -64.1 pg/mL) but the difference between groups was not statistically significant (P > 0.2).
- Effect
- Benefit
- Duration
- 12 days
- Dose
- 12.8 mg
- Population
- Adults
- Participants
- 48
RCTEffect of treatment with zinc gluconate or zinc acetate on experimental and natural colds2000n=281
A controlled study comparing zinc gluconate and zinc acetate formulations for reducing severity and duration of both experimental and naturally occurring colds. A study including two clinical trials examined the effects of 13.3 mg zinc gluconate, 5 mg zinc acetate, 11.5 mg zinc acetate or placebo in subjects with natural colds (n = 281) or experimental rhinovirus (n = 273). For natural colds, no formulation had any effect on cold severity or duration. For experimental colds, zinc acetate had no effect on either duration or severity whilst zinc gluconate had no effect on cold severity but did shorten median duration of illness (2.5 vs. 3.5 days, P = 0.035)
- Effect
- No Benefit
- Dose
- 13.3 mg
- Population
- Adults
- Participants
- 281
RCTRandomized, double-masked, placebo-controlled clinical study of the effectiveness of zinc acetate lozenges on common cold symptoms in allergy-tested subject1998n=101
A randomized double-masked placebo-controlled study assessing whether zinc acetate lozenges reduce the duration and severity of common cold symptoms in allergy-tested adults. A study of 101 participants found that zinc acetate lozenges significantly reduced overall cold symptom duration (mean 3.8 ± 0.2 days vs. 5.1 ± 0.4 days) when compared to placebo. Zinc led to a significantly greater reduction in cold duration in allergy-positive subjects (3.5 ± 0.5 days vs. 7.6 ± 1.1 days) compared to allergy-negative subjects (4.7 ± 0.5 days vs. 5.5 ± 0.8 days). Zinc supplementation did not affect mean symptom severity.
- Effect
- Benefit
- Population
- Adults
- Participants
- 101
RCTZinc gluconate lozenges for treating the common cold. A randomized, double-blind, placebo-controlled study1996n=50
A study of 100 participants (who developed symptoms of the common cold within 24 hours of study enrollment) found that zinc gluconate (13.3 mg every 2 hours whilst symptomatic) reduced the severity and length of colds (Median 4.4 days vs 7.6 days, P < 0.001) compared to placebo. The zinc group experienced a reduction in days with coughing (Median 2.0 days vs. 4.5 days, P = 0.04), headache (2.0 days vs 3.0 days, P = 0.02), hoarseness (2.0 days vs. 3.0 days, P = 0.02), nasal congestion (4.0 days vs. 6.0 days, P = 0.002), nasal drainage (4.0 days vs 7.0 days, P < 0.001), and sore throat (1.0- days vs 3.0 days, P < 0.001). Zinc did not significantly improve time to resolution for symptoms including fever, muscle ache, scratchy throat or sneezing. Compared to placebo, the zinc group had more total side effects (90% vs. 62%, P < 0.001), including nausesa (20% vs. 4%, P = 0.02), and bad-taste reactions (80% vs. 30%, P < 0.001).
- Effect
- Benefit
- Dose
- 13.3 mg
- Population
- Adults
- Participants
- 50
RCTZinc gluconate and the common cold: a controlled clinical study1992n=73
In 73 young adults, zinc gluconate-glycine lozenges shortened cold duration by 1.2 days (4.9 vs 6.1 days on placebo), with greater benefit when started within 1 day of symptom onset.
- Effect
- Benefit
- Duration
- 7 days
- Population
- Young adults
- Participants
- 73
Controlled trialZinc gluconate lozenges for common cold. A double-blind clinical trial1990n=463
In 130 adults completing a cold trial, zinc gluconate lozenges (4.5 mg every 1–1.5 hours) did not significantly reduce cold duration or severity versus placebo.
- Effect
- No Benefit
- Duration
- 10 days
- Dose
- 4.5 mg
- Population
- Adults
- Participants
- 463
RCTProphylaxis and treatment of rhinovirus colds with zinc gluconate lozenges1987n=57
In this study, volunteers underwent three protocols: A zinc gluconate lozenge tolerance study, a prophylaxis study examining the effect of zinc for the prevention of rhionvirus infection and a therapeutic study examining the effects of zinc following virus inoculation. The therapeutic study including 69 participants infected with rhinovirus-2 found zinc gluconate (23 mg lozenge every 2 hours while awake for 6 days) reduced mean daily clinical score and nasal secretion weight in 12 patients who developed colds, when compared to placebo. In the prophylaxis study including 57 volunteers, zinc gluconate resulted in a reduction in total mean clinical score from 8.2 in the placebo group to 5.7. Participants were infected with rhinovirus 2 (HRV-2 on the second day of medication (zinc gluconate was dosed 23 mg every 2 h while awake for 4.5 days). Taking zinc in the 24 h leading up to a common cold may reduce like likelihood of catching a cold.
- Effect
- Benefit
- Duration
- 6 days
- Dose
- 23 mg
- Participants
- 57
RCTReduction in duration of common colds by zinc gluconate lozenges in a double-blind study1984n=65
A double-blind clinical trial reporting that zinc gluconate lozenges significantly reduce common cold duration compared with placebo. A study including 65 subjects (adults & children) found that zinc gluconate (Loading dose of 47 mg [2 tablets] then 23.5 mg every 2 hours whilst awake, up to 282 mg/day for adults, 211.5 mg/day for youths & 141 mg/day for children under 60 lbs/27.2 kg) resulted in complete resolution of cold symptoms after 7 days, in 86% of those in the zinc group when compared to 46% of participants in the placebo group.
- Effect
- Benefit
- Duration
- 7 days
- Dose
- 282 mg/day
- Population
- Adults
- Participants
- 65
EleutheroView supplement →
Reconsider purchase·★★★★★
How we scored this▸
- Taking the herbal combination Kan Jang, which includes eleuthero and andrographis, soon after cold symptoms start can help relieve symptoms faster and shorten the duration of the cold.
- Some improvement can be seen within 2 days, with full relief in about 4-5 days.
- Studies in children show it works better than echinacea or no treatment.
- It’s not clear if eleuthero or andrographis alone provides these benefits.
Browse 4 studies
Systematic reviewAndrographis paniculata in the symptomatic treatment of uncomplicated upper respiratory tract infection: systematic review of randomized controlled trials2004n=433
A systematic review of 433 participants in 3 RCTs found Andrographis paniculata alone or with A. senticosus significantly reduced URTI symptom severity versus placebo.
- Effect
- Benefit
- Population
- Patients with upper respiratory tract infection
- Participants
- 433
RCTComparative controlled study of Andrographis paniculata fixed combination, Kan Jang and an Echinacea preparation as adjuvant, in the treatment of uncomplicated respiratory disease in children2004n=53
In 130 children (4–11 years) over 10 days, adjuvant Kan Jang significantly improved cold symptoms, nasal secretion, and recovery time versus adjuvant echinacea or standard treatment alone.
- Effect
- Benefit
- Duration
- 10 days
- Population
- Children/adolescents
- Participants
- 53
- Ages
- 4–11
RCTA double blind, placebo-controlled study of Andrographis paniculata fixed combination Kan Jang in the treatment of acute upper respiratory tract infections including sinusitis2002n=90
In 185 adults with acute URTI/sinusitis over 5 days, Kan Jang significantly improved total symptom scores versus placebo, with greatest effects on headache, nasal, throat symptoms, and malaise.
- Effect
- Benefit
- Duration
- 5 days
- Population
- Adults
- Participants
- 90
RCTDouble-blind, placebo-controlled pilot and phase III study of activity of standardized Andrographis paniculata Herba Nees extract fixed combination (Kan jang) in the treatment of uncomplicated upper-respiratory tract infection2000n=179
In pilot and phase III trials (225 patients), Kan Jang significantly improved total symptom and diagnosis scores versus placebo, with throat symptoms showing the largest benefit.
- Effect
- Benefit
- Population
- Patients with upper respiratory tract infections
- Participants
- 179
GarlicView supplement →
Reconsider purchase·★★★★★
How we scored this▸
- Taking one garlic capsule daily during the winter may help reduce how often people get a cold.
- One study found that people taking garlic had about 63% fewer colds and recovered about a day faster than those taking a placebo.
- Another study in older adults showed fewer cold episodes in those taking a garlic and onion supplement.
- Garlic supplements may cause a garlic odor or sometimes a rash.
- While these findings are promising, more research is needed to fully confirm garlic’s benefits for preventing colds.
Browse 3 studies
Beneficial Effects of Daily Consumption of Garlic and Onion Extract Concentrate on Infectious Respiratory Diseases in Elderly Resident Volunteers2023n=65
In a 36-week trial of 65 elderly care residents, daily garlic-and-onion extract concentrate reduced incidence of infectious respiratory diseases versus placebo.
- Effect
- Benefit
- Duration
- 36 weeks
- Population
- Healthy adults
- Participants
- 65
RCTSupplementation with aged garlic extract improves both NK and γδ-T cell function and reduces the severity of cold and flu symptoms: a randomized, double-blind, placebo-controlled nutrition intervention2012n=56
In a 90-day double-blind RCT of 120 healthy adults, 2.56 g/day aged garlic extract improved NK and gamma-delta T cell proliferation and reduced cold and flu symptom burden versus placebo.
- Effect
- Benefit
- Dose
- 2.56 g/day
- Population
- Healthy adults
- Participants
- 56
RCTPreventing the common cold with a garlic supplement: a double-blind, placebo-controlled survey2001n=46
In a 12-week double-blind RCT of 146 volunteers, allicin-containing garlic supplement reduced colds (24 vs 65) and shortened illness duration (1.5 vs 5 days) versus placebo.
- Effect
- Benefit
- Duration
- 12 weeks
- Population
- Healthy adults
- Participants
- 46
EchinaceaView supplement →
Reconsider purchase·★★★★★
How we scored this▸
- Echinacea may help reduce the chances of catching a cold by a small to moderate amount.
- A large study found that taking a particular echinacea product for several months led to fewer colds and shorter cold symptoms.
- Smaller studies also suggest it might help prevent colds, but results are less clear.
- When people are exposed to cold viruses on purpose, echinacea does not seem to prevent colds.
- For treating colds, some smaller studies suggest echinacea might slightly reduce symptoms and make colds shorter by a day or two.
Browse 22 studies·2 meta-analyses
ObservationalReduction of Viral Load in Patients with Acute Sore Throats: Results from an Observational Clinical Trial with Echinacea/Salvia Lozenges2023n=18
In 74 patients with acute sore throat treated with Echinacea/Salvia lozenges for 4 days, throat pain fell 48% after one lozenge; in 18 virus-positive patients, viral load dropped 96% by day 4.
- Effect
- Benefit
- Duration
- 4 days
- Dose
- 4000 mg Echinacea + 1893 mg Salvia/day
- Population
- Healthy adults
- Participants
- 18
- Ages
- 13–69
RCTEchinacea reduces antibiotic usage in children through respiratory tract infection prevention: a randomized, blinded, controlled clinical trial2021n=103
In 103 children (ages 4–12) over two 2-month prevention periods, Echinacea purpurea 1,200 mg/day reduced respiratory infection episodes by 32.5%, antibiotic use by 76.3%, and influenza detections versus vitamin C control.
- Effect
- Benefit
- Duration
- 1 week
- Dose
- 200 mg/day
- Population
- Children/adolescents
- Participants
- 103
- Ages
- 4–12
MetaEchinacea for preventing and treating the common cold2014n=4,631
A Cochrane review of 24 RCTs (4,631 participants) found no individual prevention trial showed significant cold reduction, though pooled trends suggested a 10–20% relative risk reduction; treatment trials showed minimal benefit.
- Effect
- No Benefit
- Population
- Healthy adults
- Participants
- 4,631
RCTSafety and Efficacy Profile of Echinacea purpurea to Prevent Common Cold Episodes: A Randomized, Double-Blind, Placebo-Controlled Trial2012n=755
In 755 healthy adults over 4 months, E. purpurea extract was noninferior to placebo for safety and significantly reduced total cold episodes, episode days, and pain-killer use, especially preventing enveloped virus infections.
- Effect
- Benefit
- Duration
- 4 months
- Population
- Healthy adults
- Participants
- 755
- Ages
- 18+
RCTEchinacea for treating the common cold: a randomized trial2010n=719
In 719 patients (ages 12–80) with new-onset colds, echinacea at 10.2 g/day on day 1 did not significantly reduce illness severity (P = 0.089) or duration (P = 0.075) versus blinded placebo.
- Effect
- No Benefit
- Dose
- 10.2 g/day
- Population
- Adults
- Participants
- 719
- Ages
- 12–80
RCTEffects of echinacea on the frequency of upper respiratory tract symptoms: a randomized, double-blind, placebo-controlled trial2008n=90
In 58 hospital workers over 8 weeks, E. purpurea 6 capsules/day did not significantly reduce sick days (9 vs 14 days per person) compared with parsley placebo (p = 0.67).
- Effect
- No Benefit
- Duration
- 8 weeks
- Dose
- 6 capsules/day
- Population
- Women
- Participants
- 90
- Ages
- 18–65
MetaEvaluation of echinacea for the prevention and treatment of the common cold: a meta-analysis2007
A meta-analysis of 14 studies found echinacea decreased cold incidence by 58% (OR 0.42) and shortened cold duration by 1.4 days, though heterogeneity was high.
- Effect
- Benefit
MetaEchinacea for preventing and treating the common cold2006
A Cochrane review of 16 trials found no prevention benefit from echinacea, but aerial-part E. purpurea preparations showed some evidence for early treatment of colds in adults, with inconsistent results across preparations.
- Effect
- Benefit
- Population
- Adults
MetaEchinacea in the prevention of induced rhinovirus colds: a meta-analysis2006
A meta-analysis of 3 experimental rhinovirus challenge studies found echinacea reduced symptomatic cold odds by 55% (OR 1.55 for placebo vs echinacea) but did not significantly reduce total symptom scores.
- Effect
- Benefit
- Population
- Adults
Controlled trialA proprietary extract from the echinacea plant (Echinacea purpurea) enhances systemic immune response during a common cold2005
In patients with naturally acquired colds treated with Echinilin echinacea or placebo for 7 days, echinacea reduced total symptom scores and increased circulating white blood cells and NK cells versus placebo.
- Effect
- Benefit
- Duration
- 7 days
- Dose
- 5 mL/dose; 8 doses day 1, 3 doses/day days 2–7
- Population
- Adults
RCTAn evaluation of Echinacea angustifolia in experimental rhinovirus infections2005n=437
In 437 volunteers experimentally inoculated with rhinovirus, three E. angustifolia root extracts (prophylactic or treatment) showed no significant effects on infection rates, symptom severity, or nasal inflammatory markers.
- Effect
- No Benefit
- Participants
- 437
RCTEchinacea purpurea for prevention of experimental rhinovirus colds2004n=48
In 48 healthy adults challenged with rhinovirus, prophylactic echinacea did not reduce infection rate (92% vs 95%) or cold incidence (58% vs 82%, P = 0.114) versus placebo.
- Effect
- No Benefit
- Duration
- 7 days
- Dose
- 2.5 mL 3 times/day
- Population
- Healthy adults
- Participants
- 48
RCTEchinacea purpurea therapy for the treatment of the common cold: a randomized, double-blind, placebo-controlled clinical trial2004n=28
In 128 adults with colds treated with E. purpurea 300 mg/day or placebo for up to 14 days, echinacea did not significantly reduce total symptom scores or time to resolution (P = 0.73).
- Effect
- No Benefit
- Duration
- up to 14 days
- Dose
- 300 mg/day
- Population
- Adults
- Participants
- 28
RCTEfficacy of a standardized echinacea preparation (Echinilin) for the treatment of the common cold: a randomized, double-blind, placebo-controlled trial2004n=128
In 128 adults with naturally acquired colds, standardized echinacea (Echinilin) reduced total daily symptom scores by 23.1% versus placebo (P < 0.01) when taken at symptom onset for 7 days.
- Effect
- Benefit
- Duration
- 7 days
- Population
- Adults
- Participants
- 128
- Ages
- 18–65
RCTEfficacy and safety of echinacea in treating upper respiratory tract infections in children: a randomized controlled trial2003n=407
In 407 children (ages 2–11) with URIs over 4 months, E. purpurea did not reduce URI duration (9 days both groups) or severity, and was associated with increased rash (7.1% vs 2.7%, P = 0.008).
- Effect
- No Benefit
- Duration
- 4 months
- Population
- Children/adolescents
- Participants
- 407
- Ages
- 2–11
RCTTreatment of the common cold with unrefined echinacea. A randomized, double-blind, placebo-controlled trial2002
In 148 college students with colds, unrefined echinacea (1 g six times on day 1, then 3× daily) did not significantly reduce symptom duration (6.27 vs 6.01 days) or severity versus placebo.
- Effect
- No Benefit
- Duration
- up to 10 days
- Dose
- 1 g/day
RCTEfficacy of Echinacea purpurea in patients with a common cold. A placebo-controlled, randomised, double-blind clinical trial2001n=80
In 80 adults with common colds, EC31J0 echinacea significantly shortened time to complete cold picture (median 6 vs 9 days with placebo, one-sided p = 0.011) and was well tolerated.
- Effect
- Benefit
- Population
- Adults
- Participants
- 80
RCTIneffectiveness of echinacea for prevention of experimental rhinovirus colds2000
In an experimental rhinovirus challenge, echinacea did not significantly reduce infection rate (44% vs 57%) or illness rate (36% vs 43%) compared with placebo.
- Effect
- No Benefit
RCTThe efficacy of echinacea compound herbal tea preparation on the severity and duration of upper respiratory and flu symptoms: a randomized, double-blind placebo-controlled study2000n=95
In 95 adults with early cold or flu symptoms over 5 days, Echinacea Plus tea (5–6 cups/day) significantly reduced symptom duration and severity versus placebo (p < 0.001), with no adverse effects reported.
- Effect
- Benefit
- Duration
- 5 days
- Population
- Adults
- Participants
- 95
RCTA randomized controlled trial of the effect of fluid extract of Echinacea purpurea on the incidence and severity of colds and respiratory infections1999n=109
In 108 adults with frequent colds over 8 weeks, E. purpurea fluid extract (8 mL twice daily) did not significantly reduce cold incidence (65% vs 74%), duration (4.5 vs 6.5 days), or severity versus placebo.
- Effect
- No Benefit
- Duration
- 8 weeks
- Dose
- 4 mL twice/day
- Population
- Healthy adults
- Participants
- 109
RCTEchinaforce and other Echinacea fresh plant preparations in the treatment of the common cold. A randomized, placebo controlled, double-blind clinical trial1999n=246
In 246 adults with common colds treated for up to 7 days, Echinaforce and its concentrated preparation significantly reduced symptom scores versus placebo and a special radix extract, with good tolerability.
- Effect
- Benefit
- Duration
- up to 7 days
- Population
- Adults
- Participants
- 246
RCTEchinacea root extracts for the prevention of upper respiratory tract infections: a double-blind, placebo-controlled randomized trial1998n=18
In 302 healthy adults over 12 weeks, echinacea root extracts did not significantly delay time to first URTI (66–69 vs 65 days) or reduce infection rate (~29–32% vs 37% placebo), though subjects perceived greater benefit.
- Effect
- No Benefit
- Duration
- 12 weeks
- Population
- Healthy adults
- Participants
- 18
ElderberryView supplement →
Reconsider purchase·★★★★★
How we scored this▸
- No summary is available.
Browse 1 study
RCTElderberry Supplementation Reduces Cold Duration and Symptoms in Air-Travellers: A Randomized, Double-Blind Placebo-Controlled Clinical Trial2016n=25
In 312 economy-class air travelers, elderberry extract significantly reduced cold duration (57 vs 117 days) and average symptom scores (247 vs 583) versus placebo, though cold episode counts did not differ significantly.
- Effect
- Benefit
- Population
- Pregnant women
- Participants
- 25
- Ages
- 18+
Green TeaView supplement →
Reconsider purchase·★★★★★
How we scored this▸
- Drinking a lot of green tea is linked to a slightly lower risk of colon cancer but not rectal cancer.
- Women who drink green tea may have a stronger reduction in colon and rectal cancer risk.
- These benefits are mostly seen in studies from Asia, where people drink green tea regularly.
- Results from studies in other parts of the world are mixed.
- Smoking and gender might influence how green tea affects cancer risk.
Browse 1 study
RCTSpecific formulation of Camellia sinensis prevents cold and flu symptoms and enhances gamma,delta T cell function: a randomized, double-blind, placebo-controlled study2007
In a 3-month double-blind RCT, a Camellia sinensis (green tea) capsule formulation reduced cold and flu symptom incidence and enhanced gamma-delta T-cell function versus placebo.
- Effect
- Benefit
- Duration
- 3 months
- Population
- Healthy adults
- Ages
- 18–70
Panax GinsengView supplement →
Reconsider purchase·★★★★★
How we scored this▸
- Early research shows that taking 200 mg daily of a specific Panax ginseng extract (G115), starting 4 weeks before a flu shot and continuing for 8 weeks after, can lower the chance of getting the flu or a common cold by 65% compared to not taking it.
Browse 1 study
RCTEfficacy and safety of the standardised Ginseng extract G115 for potentiating vaccination against the influenza syndrome and protection against the common cold [corrected]1996n=227
In 227 adults, ginseng G115 100 mg/day for 12 weeks with flu vaccination cut cold/flu cases (15 vs 42, p<0.001) and raised antibody titres and NK cell activity versus placebo.
- Effect
- Benefit
- Duration
- 12 weeks
- Dose
- 100 mg/day
- Population
- Adults
- Participants
- 227
Vitamin DView supplement →
Reconsider purchase·★★★★★
How we scored this▸
- Vitamin D is possibly effective for Common cold.
Browse 7 studies
RCTEffect of Vitamin D supplementation to reduce respiratory infections in children and adolescents in Vietnam: A randomized controlled trial2019n=1,300
In 1,300 Vietnamese children given 14,000 IU/week for 8 months, vitamin D did not reduce influenza but modestly reduced non-influenza respiratory viral infections (HR 0.76).
- Effect
- Benefit
- Duration
- 8 months
- Dose
- 2000 IU/day
- Population
- Children/adolescents
- Participants
- 1,300
- Ages
- 3–17
RCTIntake of 25-Hydroxyvitamin D3 Reduces Duration and Severity of Upper Respiratory Tract Infection: A Randomized, Double-Blind, Placebo-Controlled, Parallel Group Comparison Study2018n=28
In 215 Japanese adults with low 25(OH)D given 10 µg/day 25-hydroxyvitamin D3 for 16 weeks, supplementation shortened URTI duration and improved symptom severity versus placebo.
- Effect
- Benefit
- Dose
- 10 mcg/day
- Population
- Adults
- Participants
- 28
- Ages
- 45–74
RCTEffect of High-Dose vs Standard-Dose Wintertime Vitamin D Supplementation on Viral Upper Respiratory Tract Infections in Young Healthy Children2017n=49
In 703 Canadian children aged 1–5 given 2000 versus 400 IU/day for ≥4 months, high-dose vitamin D did not reduce laboratory-confirmed upper respiratory infections.
- Effect
- No Benefit
- Dose
- 400 IU/day
- Population
- Children/adolescents
- Participants
- 49
- Ages
- 1–5
RCTVitamin D Supplementation and the Risk of Colds in Patients with Asthma2016n=203
In 203 adults with asthma given 100,000 IU load plus 4000 IU/day for 28 weeks, vitamin D did not reduce cold severity or frequency; African Americans had higher cold rates.
- Effect
- No Benefit
- Duration
- 28 weeks
- Dose
- 4000 IU/day
- Population
- Adults
- Participants
- 203
RCTDouble-blind randomised controlled trial of vitamin D3 supplementation for the prevention of acute respiratory infection in older adults and their carers (ViDiFlu)2015n=103
In 240 older adults given bolus plus daily vitamin D for 1 year, high-dose supplementation did not prevent ARIs but increased upper respiratory infection risk and symptom duration.
- Effect
- No Benefit
- Duration
- 1 year
- Dose
- 10 μg/day
- Population
- Older adults
- Participants
- 103
RCTVitamin D3 and gargling for the prevention of upper respiratory tract infections: a randomized controlled trial2014n=85
In 600 university students given 10,000 IU/week vitamin D for ~2 months, vitamin D nonsignificantly reduced clinical URTIs but significantly lowered laboratory-confirmed infection risk (RR 0.54).
- Effect
- Benefit
- Dose
- 10000 IU/week
- Population
- Pregnant women
- Participants
- 85
RCTVitamin D3 supplementation and upper respiratory tract infections in a randomized, controlled trial2013n=2,228
In 759 adults given 1000 IU/day vitamin D in a colorectal adenoma trial, supplementation did not reduce winter upper respiratory tract infection episodes or duration over 4–5 years.
- Effect
- No Benefit
- Dose
- 1000 IU/day
- Population
- Adults
- Participants
- 2,228
- Ages
- 45–75
Evidence visualised
Same ratings as above, aggregated so you can see coverage and imbalance.
| Supplement | DEX | Studies | Meta-analyses | Share |
|---|---|---|---|---|
| Echinacea | ★★★★★44% | 22 | 2 | 31% |
| Vitamin C | ★★★★★68% | 19 | 2 | 26% |
| Zinc | ★★★★★68% | 14 | 1 | 19% |
| Vitamin D | ★★★★★40% | 7 | 0 | 10% |
| Eleuthero | ★★★★★52% | 4 | 0 | 6% |
| Garlic | ★★★★★48% | 3 | 0 | 4% |
| Elderberry | ★★★★★44% | 1 | 0 | 1% |
| Green Tea | ★★★★★44% | 1 | 0 | 1% |
| Panax Ginseng | ★★★★★44% | 1 | 0 | 1% |