Vitamin C Supplementation: Clinical Benefits and Indications in Adults
Vitamin C supplementation has demonstrated benefits primarily in the treatment or prevention of vitamin C deficiency (including scurvy) and in reducing the duration of the common cold during regular prophylaxis. Vitamin C supplementation has not demonstrated cardiovascular event reduction in randomized evidence. [1], [2], [3]
Indications: Vitamin C Deficiency and Scurvy
Vitamin C supplementation is indicated for treatment of vitamin C deficiency states, including scurvy, because vitamin C replacement is the only effective therapy. MedlinePlus Drug Information: Ascorbic acid
Clinical deficiency sufficient to cause scurvy is rare in developed countries. [4]
Indications: Common Cold—Routine Regular Supplementation
Regular prophylactic vitamin C supplementation has demonstrated a reduction in the duration of common cold illness in adults. [2]
Regular prophylaxis has shown no consistent reduction in common cold incidence in the general community population. [2]
Therapeutic vitamin C started after onset of cold symptoms has not demonstrated consistent benefit on cold duration or severity in randomized comparisons. [2]
Demonstrated Clinical Benefits: Common Cold Effect Sizes
In placebo-controlled trials of the general adult community, prophylactic vitamin C showed a pooled reduction in developing a cold of no meaningful magnitude (pooled RR 0.97, 95% CI 0.94 to 1.00). [2]
Across adult episodes in prophylaxis trials, vitamin C reduced common cold duration by 8% (95% CI 3% to 12%). [2]
Indications: High-Physiologic-Stress States (Exercise/Cold Exposure Subgroups)
Vitamin C supplementation has demonstrated reduced risk of developing a cold in subgroups exposed to brief periods of severe physical exercise and cold environments. [2]
In these subgroup trials, pooled incidence showed benefit (pooled RR 0.48, 95% CI 0.35 to 0.64). [2]
Indications: Contrast-Associated Acute Kidney Injury (Contrast-Induced Nephropathy)
Vitamin C supplementation has been associated with reduced incidence of contrast-induced nephropathy after coronary angiography in a systematic review and meta-analysis. [5]
In that meta-analysis, the pooled odds ratio for contrast-induced nephropathy with vitamin C was 0.63 (95% CI 0.45 to 0.89). [5]
A pooled mortality reduction was not demonstrated in that meta-analysis. [5]
Lack of Demonstrated Cardiovascular Outcome Benefit
Vitamin C supplementation has not demonstrated cardiovascular benefit in randomized evidence syntheses, including no effect on cardiovascular or type 2 diabetes risk in a comprehensive micronutrient meta-analysis. [6]
An updated systematic review of vitamin and mineral supplementation for cardiovascular disease prevention and treatment also reported no effect for vitamin C on cardiovascular outcomes and all-cause mortality. [3]
Practical Indication Boundaries
Routine vitamin C supplementation for common cold prevention in community-dwelling adults has not been supported due to lack of reduction in cold incidence. [2]
Vitamin C supplementation after cold symptom onset has not shown consistent clinical benefit. [2]
Treatment-directed use is supported for vitamin C deficiency states because vitamin C replacement addresses the underlying etiology of scurvy. MedlinePlus Drug Information: Ascorbic acid