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Vc8.5
Vitamin C Research
Probably helpsHigh safety
36 peer-reviewed studies
What the evidence says
Probably helps
Vitamin C helped in about half (10/15) of the studies that measured an effect — promising, but not unanimous.
Most evidence is from high-quality meta-analyses and randomised trials published 1997–2026 with a typical study size of 498 participants.
Based on 36 studies · 16 meta-analyses · 7 RCTs · 48,354 total participants
Confidence
High
What the studies found
10helped4unclear1didn't help· 21 more without graded effect data
By outcome
Immune supportMay reduce cold duration by 8% in adults · Ongoing supplementation
Probably helps11 studies
RecoveryReduces oxidative stress from intense exercise · 1-2 weeks
Probably helps7 studies
Safety profile
Mostly mechanism / observational5 studies
Therapeutic & clinical
Mostly mechanism / observational4 studies
Skin healthSupported collagen synthesis and skin protection within 4-8 weeks · 4-8 weeks
While evidence from short-term studies suggests that vitamin C supplementation may improve glycemic control and BP in people with type 2 diabetes, vitamin C supplementation cannot currently be recommended as a therapy until larger, long-term, and high-quality trials confirm these findings.
Mason SA et al. · Diabetes care (2021)
While evidence from short-term studies suggests that vitamin C supplementation may improve glycemic control and BP in people with type 2 diabetes, vitamin C supplementation cannot currently be recommended as a therapy until larger, long-term, and high-quality trials confirm these findings.
4Mortality due to pneumoniaMeta-AnalysisCited 30×n=2,774 · very large study2020
Due to the small number of included studies and very low quality of the existing evidence, we are uncertain of the effect of vitamin C supplementation for the prevention and treatment of pneumonia.
Padhani ZA et al. · The Cochrane database of systematic reviews (2020)
No clear effect
← WorseNo effectBetter →
We are uncertain of the effect of vitamin C supplementation on mortality due to pneumonia (RR 0.21, 95% CI 0.03 to 1.66; 1 study, 57 participants; very low-quality evidence).
Further good-quality studies are required to assess the role of vitamin C supplementation in the prevention and treatment of pneumonia.
5Term PROM with vitamin C and E supplementationMeta-AnalysisCited 109×n=20,038 · very large study2015
The data do not support routine vitamin C supplementation alone or in combination with other supplements for the prevention of fetal or neonatal death, poor fetal growth, preterm birth or pre-eclampsia.
Rumbold A et al. · The Cochrane database of systematic reviews (2015)
Huge harm
← WorseNo effectBetter →
Conversely, the risk of term PROM was increased when supplementation included vitamin C and vitamin E (average RR 1.73, 95% CI 1.34 to 2.23; 3060 participants; two studies; I² = 0%).
The data do not support routine vitamin C supplementation alone or in combination with other supplements for the prevention of fetal or neonatal death, poor fetal growth, preterm birth or pre-eclampsia.
Further research is required to elucidate the possible role of vitamin C in the prevention of placental abruption and prelabour rupture of membranes.
8Digestive system cancer riskMeta-AnalysisCited 9×n=498 · medium study2024
Plasma vitamin C has a significant reduction effect on the incidence of gastric cancer only, but additional large-scale clinical studies are needed to determine its impact on the incidence of DSCs.
Zhong J et al. · Food & function (2024)
Noticeable benefit
← WorseNo effectBetter →
Vitamin C intake significantly reduced DSCs risk (RR = 0.88, 95% confidence interval (CI) 0.83 to 0.93).
These estimates suggest that vitamin C intake could significantly reduce gastrointestinal cancer incidence, including OPE, gastric, and colon cancers.
Plasma vitamin C has a significant reduction effect on the incidence of gastric cancer only, but additional large-scale clinical studies are needed to determine its impact on the incidence of DSCs.
However, further research is required to conclusively establish its effects on immune health.
Calder PC et al. · Nutrients (2025)
Most studies (77%) had a low risk of bias.
In conclusion, the type and delivery modality of vitamin C can impact its bioavailability and functionality.
Studies highlight the advantages of Calcium ascorbate EC over traditional ascorbic acid in terms of its tolerability and its potential to increase leukocyte vitamin C concentrations, crucial for immune function and protection against infection.
11CRPS-I prevalence after limb surgeryMeta-AnalysisCited 1×2024
The results of our study showed the positive effect of VC supplementation in reducing the prevalence of CRPS-I after limb surgery.
Ranjbar Moghaddam M et al. · International journal of orthopaedic and trauma nursing (2024)
The meta-analysis revealed that VC supplementation have effect on reducing CRPS-I post-limb surgery but this result shows that the pooled effect size is not statistically significant.
The heterogeneity of the studies was low (I2 = 26.28%, p = 0.22).
12All-cause mortality in COVID-19Meta-AnalysisCited 9×2023
Overall, evidence from RCTs suggests a survival benefit for vitamin C in patients with severe COVID-19.
Kow CS et al. · Inflammopharmacology (2023)
Large benefit
← WorseNo effectBetter →
The meta-analysis of eleven trials using a random-effects model revealed significant reduction in the risk of all-cause mortality with the administration of vitamin C among patients with COVID-19 relative to no vitamin C (pooled odds ratio = 0.53; 95% confidence interval 0.30-0.92).
Subgroup analysis of studies that included patients with severe COVID-19 also produced findings of significant mortality reduction with the administration of vitamin C relative to no vitamin C (pooled odds ratio = 0.47; 95% confidence interval 0.26-0.84).
Overall, evidence from RCTs suggests a survival benefit for vitamin C in patients with severe COVID-19.
13Stroke preventionMeta-AnalysisCited 6×n=17 · very small study2024
Our study has established noteworthy connections between vitamin A, vitamin B-complex, vitamin B6, folate, vitamin C, and vitamin D in the realm of stroke prevention.
Tripathi S et al. · European journal of clinical investigation (2024)
Our study has established noteworthy connections between vitamin A, vitamin B-complex, vitamin B6, folate, vitamin C, and vitamin D in the realm of stroke prevention.
These findings add substantial weight to the accumulating evidence supporting the potential advantages of vitamin interventions in mitigating the risk of stroke.
However, to solidify and validate these observations, additional research is imperative.
14Risk of acute respiratory infectionsMeta-AnalysisCited 63×2021
This meta-analysis examined the effects of Vitamin C.
Abioye AI et al. · BMJ global health (2021)
No clear effect
← WorseNo effectBetter →
Likely real
Vitamin D supplementation reduced the risk of ARI (risk ratio (RR)=0.97; 95% CI 0.94 to 1.00; p=0.028) and shortened the duration of symptoms (per cent difference: -6% (95% CI -9% to -2%; p=0.003)).
Vitamin C supplementation reduced the risk of ARIs (RR=0.96; 95% CI 0.93 to 0.99; p=0.01) and shortened the duration of symptoms (per cent difference: -9% (95% CI -16% to -2%; p=0.014)).
Zinc supplementation did not reduce the risk of ARIs but shortened the duration of symptoms substantially (per cent difference: -47% (95% CI -73% to -21%; p=0.0004)).
The effect size showed that vitamin C was associated with a decreased rate of CRPS-1 than placebo (odds ratio 0.33, 95% confidence interval [0.17, 0.63]).
Seth I et al. · The Journal of foot and ankle surgery : official publication of the American College of Foot and Ankle Surgeons (2022)
Huge benefit
← WorseNo effectBetter →
The effect size showed that vitamin C was associated with a decreased rate of CRPS-1 than placebo (odds ratio 0.33, 95% confidence interval [0.17, 0.63]).
Overall, vitamin C was associated with a decreased rate of CRPS-I than placebo, while no significant difference was found regarding complications, functional outcomes, and pain scores.
These results hold true when stratifying fracture type (distal radius, ankle, and foot surgeries) and vitamin C dose (500 mg or 1 g).
Studies with larger sample sizes and adequate power are still required.
Clifford T et al. · Critical reviews in food science and nutrition (2020)
No clear effect
← WorseNo effectBetter →
Could be chance
Vitamin C and/or E did not attenuate aerobic exercise induced improvements in maximal aerobic capacity (V̇O2max) (SMD -0.14, 95% CI: -0.43 to 0.15, P = 0.35) or endurance performance (SMD -0.01, 95% CI: -0.38 to 0.36, P = 0.97).
There were also no effects of these supplements on lean mass and muscle strength following RT (SMD -0.07, 95% CI: -0.36 to 0.23, P = 0.67) and (SMD -0.15, 95% CI: -0.16 to 0.46, P = 0.35), respectively.
There was also no influence of age on any of these outcomes (P > 0.05).
20Serum vitamin C levels in hypertensive vs normotensiveMeta-AnalysisCited 34×n=18 · very small study2020
People with hypertension have a relatively low serum vitamin C, and vitamin C is inversely associated with both systolic blood pressure and diastolic blood pressure.
Ran L et al. · Cardiovascular therapeutics (2020)
Noticeable benefit
← WorseNo effectBetter →
Likely real
In the evaluation of serum vitamin C levels, the concentration in hypertensive subjects is 15.13 μmol/L lower than the normotensive ones (mean difference = -15.13, 95% CI [-24.19, -6.06], and P = 0.001).
Serum vitamin C has a significant inverse relation with both systolic blood pressure (Fisher's Z = -0.17, 95% CI [-0.20, -0.15], P < 0.00001) and diastolic blood pressure (Fisher's Z = -0.15, 95% CI [-0.20, -0.10], P < 0.00001).