Vitamin C · The Ingredient Files

①

Evidence by effect

Evidence strength (A–D, color) and effect size (dots, fill) are shown separately. The two axes are independent.

Claimed effect

Evidence strength

Effect size

One-line summary · key source

Preventing and correcting vitamin C deficiency (scurvyA deficiency disease from prolonged lack of vitamin C, causing bleeding gums, bruising, and slow wound healing.)Evidence type: Established guideline

A Strong

Large

This is vitamin C's real role and the part beyond dispute. Vitamin C is a nutrient essential for collagen synthesis, and a prolonged lack causes scurvyA deficiency disease from prolonged lack of vitamin C, causing bleeding gums, bruising, and slow wound healing. (bleeding gums, bruising, slow wound healing, fatigue). In a human experiment depriving healthy adults of vitamin C for three months, scurvy signs actually developed, and they resolved once vitamin C was restored (becoming asymptomatic). The US FDA also approves ascorbic acid as the standard short-term care for scurvy. But this is the effect of filling a deficiency; adding more for someone already replete brings no extra benefit (see the effects below). PMID: 5411783 · fda-label-ascorbic-acid-injection

Preventing colds (general population)Evidence type: Meta-analysis

D Insufficient

None

Vitamin C's most famous belief, yet it does not hold for the general population. In the CochraneAn international network that rigorously reviews and synthesizes evidence. review pooling 10,708 people from general community trials, taking 0.2 g or more daily on a regular basis did not change the risk of catching a cold versus placeboAn inert dummy treatment used as the comparison baseline. (relative risk 0.97, 95% CI 0.94 to 1.00). The authors concluded that because it fails to reduce cold incidence in the general population, routine vitamin C supplementation is not justified. 'Preventing colds' must be kept separate from 'shortening duration' below. PMID: 23440782

Preventing colds in people under extreme physical stress (marathoners, soldiers)Evidence type: Meta-analysis

B Moderate

Moderate

Unlike the general population, a clear preventive effect appeared in specific groups under short, extreme physical stress. In five trials (598 people) of marathon runners, skiers, and soldiers on subarctic exercises, regular vitamin C halved the risk of colds (relative risk 0.48, 95% CI 0.35 to 0.64). The CochraneAn international network that rigorously reviews and synthesizes evidence. authors judged that vitamin C may be useful for people exposed to brief periods of severe physical exercise. However, this is a special situation and cannot be generalized to everyday life. PMID: 23440782

Reducing cold duration and severityEvidence type: Meta-analysis

C Weak

Minimal

Even without prevention, regular daily use did tend to shorten how long a cold lasted. In the CochraneAn international network that rigorously reviews and synthesizes evidence. review, regular supplementation cut cold duration by 8% (3 to 12%) in adults and 14% (7 to 21%) in children, with 1 to 2 g/day in children shortening colds by up to 18%, and severity was also reduced. But this applies to already taking it daily beforehand. In seven therapeutic trials where people started it after symptoms began, there was no consistent effect on duration or severity. The effect size itself is small, on the order of about a day. PMID: 23440782

Preventing cardiovascular disease and cancerEvidence type: RCTRandomized controlled trial - a high-reliability trial that randomly assigns participants to compare effects.

D Insufficient

None

The hope that antioxidant vitamins ward off chronic disease also collapsed in large long-term trials. In the Physicians' Health Study II (randomized, double-blind) following 14,641 male physicians for eight years, 500 mg/day of vitamin C did not reduce major cardiovascular events (hazard ratio 0.99, with myocardial infarctionA heart attack - death of heart muscle from blocked blood flow., stroke, and cardiovascular death all non-significant), nor did it reduce total or prostate cancer (cancer hazard ratio 1.01, prostate 1.02). The authors concluded there is no support for using these supplements to prevent cancer in middle-aged and older men. PMID: 18997197 · 19066368

Evidence strength A Strong · B Moderate · C Weak · D Insufficient/refuted

Effect size Large → None

②

Who benefits / who should be cautious

The statements in this section are translated directly from institutional sources (NIH-ODS, etc.), not our own interpretation. Consult a professional before use.

Benefit

Intravenous ascorbic acid injection is FDA-approved for short-term (up to one week) use for scurvyA deficiency disease from prolonged lack of vitamin C, causing bleeding gums, bruising, and slow wound healing. in patients who cannot take it orally. It is not indicated for simple vitamin C deficiency without signs of scurvy - that is, it is for filling a deficiency, not a drug where more is better. source↗

Original text

ASCOR is vitamin C indicated for the short term (up to 1 week) treatment of scurvy in adult and pediatric patients age 5 months and older for whom oral administration is not possible, insufficient or contraindicated. Limitations of Use ASCOR is not indicated for treatment of vitamin C deficiency that is not associated with signs and symptoms of scurvy.
Caution

Prolonged infusion of high-dose vitamin C can cause oxalate nephropathy and kidney stones. People with kidney disease or a history of kidney stones, the elderly, and children under two are at higher risk. source↗

Original text

Ascorbic acid has been associated with development of acute or chronic oxalate nephropathy following prolonged use of high doses of ascorbic acid infusion. Patients with renal disease including renal impairment, history of oxalate kidney stones, geriatric patients, and pediatric patients less than 2 years old may be at increased risk
Caution

People with glucose-6-phosphate dehydrogenase (G6PDGlucose-6-phosphate dehydrogenase; people deficient in this red-cell enzyme can suffer hemolysis from certain oxidative substances.) deficiency are at risk of severe hemolysisThe breaking apart of red blood cells. (destruction of red blood cells) from high-dose vitamin C. source↗

Original text

Patients with glucose-6-phosphate dehydrogenase deficiency are at risk of severe hemolysis; a reduced is recommended
Benefit

Vitamin C is cheap and safe, so there is little downside to a cold patient testing on an individual basis whether it helps them. But CochraneAn international network that rigorously reviews and synthesizes evidence. made clear this is an individual trial, not a proven remedy. source↗

Original text

given the consistent effect of vitamin C on the duration and severity of colds in the regular supplementation studies, and the low cost and safety, it may be worthwhile for common cold patients to test on an individual basis whether therapeutic vitamin C is beneficial for them.

③

Form & dosage evidence

Trial doses by effect

Cold duration (regular-use trial dose): 0.2 g/day or more (18% shorter with 1-2 g in children) [23440782]
CVD/cancer prevention (trial dose, no effect): 500 mg/day [18997197]

④

Balanced conclusion

With vitamin C, the key is to separate 'essential nutrient' from 'catch-all supplement.' A prolonged lack causes scurvyA deficiency disease from prolonged lack of vitamin C, causing bleeding gums, bruising, and slow wound healing., and filling that deficiency clearly works. But the flagship belief, preventing colds, did not hold for the general population (CochraneAn international network that rigorously reviews and synthesizes evidence. relative risk 0.97). The exception was people under extreme physical stress such as marathons and military training, whose cold risk was halved. Taking it daily in advance does shorten a cold slightly (8% in adults, 14% in children), but starting it after symptoms begin had no consistent effect. Prevention of cardiovascular disease and cancer was also not confirmed in trials of over 14,000 people. It is cheap and safe enough to try individually, but prolonged high doses carry a risk of kidney stones and oxalate nephropathy, and those with G6PDGlucose-6-phosphate dehydrogenase; people deficient in this red-cell enzyme can suffer hemolysis from certain oxidative substances. deficiency must watch for hemolysisThe breaking apart of red blood cells.. In short, vitamin C must be replenished if you are deficient, but taking more than enough does not make things better, and the recommended intake is easily met with ordinary foods such as bell peppers, kiwi, and broccoli.

Apply - Get it from food

Examples of foods rich in Vitamin C. Amounts are shown for reference against the doses used in the trials.

Note: eating these foods does not guarantee immediate treatment or prevention of any disease.

Relative to the adult recommendation (90 mg a day for men, 75 mg for women, +35 mg for smokers), here is roughly how much each food contributes. A serving or two of vegetables and fruit such as bell peppers, kiwi, and broccoli easily meets the target, so most people do not need a separate supplement. Vitamin C is sensitive to heat and water and is lost with prolonged boiling.

Red bell pepper, raw100 g ~128 mg [source]
Green bell pepper, raw100 g ~80 mg [source]
Kiwifruit, green, raw100 g ~75 mg [source]
Broccoli, boiled100 g ~65 mg [source]
Strawberries, raw100 g ~59 mg [source]
Orange, raw100 g ~53 mg [source]

⑤

Sources

Each source shows its one-line summary and key summary up front. Expand the collapsed section to read the original abstract. Every citation is verified by re-resolving through the API.

PMID 23440782 Vitamin C for preventing and treating the common cold Meta-analysis (Cochrane) · Cochrane Database Syst Rev, 2013 29 trials, 11,306 people - no cold prevention in the general population (RR 0.97), only extreme-exercise groups halved (0.48); regular use cut duration 8% (adults), 14% (children).

Key summary

A CochraneAn international network that rigorously reviews and synthesizes evidence. review settling 70 years of debate on vitamin C for the common cold (only placeboAn inert dummy treatment used as the comparison baseline.-controlled trials at 0.2 g/day or more). In 10,708 people in general community trials, regular use did not reduce cold incidence (relative risk 0.97). By contrast, in 598 people under extreme exercise such as marathoners and soldiers, the risk was more than halved (0.48). Regular use shortened duration by 8% in adults and 14% in children and reduced severity, but therapeutic trials starting after symptom onset showed no consistent effect. The authors said routine supplementation is not justified, though given its low cost and safety, cold patients may test therapeutic use on an individual basis.

Show original abstract

BACKGROUND: Vitamin C (ascorbic acid) for preventing and treating the common cold has been a subject of controversy for 70 years. OBJECTIVES: To find out whether vitamin C reduces the incidence, the duration or severity of the common cold when used either as a continuous regular supplementation every day or as a therapy at the onset of cold symptoms. MAIN RESULTS: Twenty-nine trial comparisons involving 11,306 participants contributed to the meta-analysis on the risk ratio (RR) of developing a cold whilst taking vitamin C regularly over the study period. In the general community trials involving 10,708 participants, the pooled RR was 0.97 (95% confidence interval (CI) 0.94 to 1.00). Five trials involving a total of 598 marathon runners, skiers and soldiers on subarctic exercises yielded a pooled RR of 0.48 (95% CI 0.35 to 0.64). Thirty-one comparisons examined the effect of regular vitamin C on common cold duration (9745 episodes). In adults the duration of colds was reduced by 8% (3% to 12%) and in children by 14% (7% to 21%). In children, 1 to 2 g/day vitamin C shortened colds by 18%. The severity of colds was also reduced by regular vitamin C administration. Seven comparisons examined the effect of therapeutic vitamin C (3249 episodes). No consistent effect of vitamin C was seen on the duration or severity of colds in the therapeutic trials. AUTHORS' CONCLUSIONS: 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. 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. ※ The abstract text as collected and stored via the API by the pipeline. The key summary is written based solely on this text.

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PMID 18997197 Vitamins E and C in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial Randomized controlled trial · JAMA, 2008 14,641 men, 8 years - 500 mg/day vitamin C did not reduce major cardiovascular events (hazard ratio 0.99; MI, stroke, and CV death all non-significant).

Key summary

A randomized, double-blind, placeboAn inert dummy treatment used as the comparison baseline.-controlled trial (Physicians' Health Study II) in 14,641 male physicians (aged 50+) at low cardiovascular risk. Over a mean of eight years, 500 mg/day of vitamin C showed no difference from placebo in major cardiovascular events (nonfatal MI, stroke, CV death; hazard ratio 0.99, 95% CI 0.89 to 1.11). MI (1.04), stroke (0.89), and CV death (1.02) were each non-significant, and vitamin E likewise had no effect. Contrary to the expectation from observational studies, no cardiovascular benefit of vitamin C supplementation was confirmed.

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CONTEXT: Basic research and observational studies suggest vitamin E or vitamin C may reduce the risk of cardiovascular disease. OBJECTIVE: To evaluate whether long-term vitamin E or vitamin C supplementation decreases the risk of major cardiovascular events among men. DESIGN, SETTING, AND PARTICIPANTS: The Physicians' Health Study II was a randomized, double-blind, placebo-controlled factorial trial of vitamin E and vitamin C that began in 1997 and continued until its scheduled completion on August 31, 2007. There were 14,641 US male physicians enrolled, who were initially aged 50 years or older. INTERVENTION: Individual supplements of 400 IU of vitamin E every other day and 500 mg of vitamin C daily. RESULTS: During a mean follow-up of 8 years, there were 1245 confirmed major cardiovascular events. There also was no significant effect of vitamin C on major cardiovascular events (active and placebo vitamin E groups, 10.8 and 10.9 events per 1000 person-years, respectively; HR, 0.99 [95% CI, 0.89-1.11]; P = .91), as well as total myocardial infarction (HR, 1.04 [95% CI, 0.87-1.24]; P = .65), total stroke (HR, 0.89 [95% CI, 0.74-1.07]; P = .21), and cardiovascular mortality (HR, 1.02 [95% CI, 0.85-1.21]; P = .86). ※ The abstract text as collected and stored via the API by the pipeline. The key summary is written based solely on this text.

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PMID 19066368 Vitamins E and C in the prevention of prostate and total cancer in men: the Physicians' Health Study II randomized controlled trial Randomized controlled trial · JAMA, 2009 14,641 men, 8 years - 500 mg/day vitamin C did not reduce total or prostate cancer (cancer hazard ratio 1.01, prostate 1.02).

Key summary

A randomized, double-blind trial examining cancer prevention in the same cohort (Physicians' Health Study II, 14,641 male physicians). Over a mean of eight years, 500 mg/day of vitamin C did not reduce total cancer (hazard ratio 1.01, 95% CI 0.92 to 1.10) or prostate cancer (1.02), and had no effect on colorectal, lung, or other site-specific cancers. Adjusting for adherence and excluding early follow-up did not change the results. The authors concluded there is no support for vitamin C or E supplementation to prevent cancer in middle-aged and older men.

Show original abstract

CONTEXT: Vitamins E and C are among the most common individual supplements. No previous trial in men at usual risk has examined vitamin C alone in the prevention of cancer. OBJECTIVE: To evaluate whether long-term vitamin E or C supplementation decreases risk of prostate and total cancer events among men. DESIGN, SETTING, AND PARTICIPANTS: The Physicians' Health Study II is a randomized, double-blind, placebo-controlled factorial trial of vitamins E and C that began in 1997 and continued until its scheduled completion on August 31, 2007. A total of 14,641 male physicians in the United States initially aged 50 years or older were enrolled. INTERVENTION: Individual supplements of 400 IU of vitamin E every other day and 500 mg of vitamin C daily. RESULTS: During a mean follow-up of 8.0 years, there were 1008 confirmed incident cases of prostate cancer and 1943 total cancers. There was also no significant effect of vitamin C on total cancer (active and placebo vitamin C groups, 17.6 and 17.5 events per 1000 person-years; HR, 1.01; 95% CI, 0.92-1.10; P = .86) or prostate cancer (active and placebo vitamin C groups, 9.4 and 9.2 cases per 1000 person-years; HR, 1.02; 95% CI, 0.90-1.15; P = .80). Neither vitamin E nor vitamin C had a significant effect on colorectal, lung, or other site-specific cancers. CONCLUSIONS: In this large, long-term trial of male physicians, neither vitamin E nor C supplementation reduced the risk of prostate or total cancer. These data provide no support for the use of these supplements for the prevention of cancer in middle-aged and older men. ※ The abstract text as collected and stored via the API by the pipeline. The key summary is written based solely on this text.

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PMID 5411783 Autonomic reflexes and vascular reactivity in experimental scurvy in man Human experimental study · J Clin Invest, 1970 Depriving five normal adults of vitamin C for three months produced scurvyA deficiency disease from prolonged lack of vitamin C, causing bleeding gums, bruising, and slow wound healing. signs, which resolved to asymptomatic after four months of repletion - a human experiment directly showing deficiency causes scurvy and repletion reverses it.

Key summary

Although its primary aim was the effect of vitamin C deficiency on autonomic and vascular reactivity, this is a classic experiment that directly documents the deficiency-repletion relationship of scurvyA deficiency disease from prolonged lack of vitamin C, causing bleeding gums, bruising, and slow wound healing. in humans. Depriving five normal volunteers of vitamin C for three months produced the symptoms and signs of scurvy, with plasma ascorbic acid falling to 0.178 mg/100 mL. After four months of vitamin C repletion they became asymptomatic and plasma levels recovered to 1.68 mg/100 mL. In other words, the causal chain that stopping vitamin C produces scurvy and restoring it resolves scurvy was confirmed under controlled human conditions. (Incidentally, deficiency did not interrupt autonomic reflexes and reduced only vascular constrictor responsiveness.)

Show original abstract

Ascorbic acid is a required cofactor in the conversion of dopamine to norepinephrine in vitro, and the deficiency of this vitamin in guinea pigs is associated with degeneration of autonomic ganglion cells and with cardiac supersensitivity to norepinephrine. Because of these findings, we tested the hypothesis that ascorbic acid deficiency in man alters autonomic cardiovascular reflexes and vasomotor responses to adrenergic stimuli. We studied five normal volunteers who had been deprived of ascorbic acid for a period of 3 months; they had developed symptoms and signs of scurvy and their plasma levels of ascorbic acid averaged 0.178 +/-SE 0.07 mg/100 ml. We repeated the studies after giving the subjects vitamin C for a period of 4 months; they had become asymptomatic and their plasma ascorbic acid had increased to an average of 1.68 +/-0.151 mg/100 ml. The results suggest that the decreased vascular responsiveness to intra-arterial norepinephrine and tyramine and to lower body negative pressure during ascorbic acid deficiency is caused by a defect in the ability of resistance vessels to constrict in response to adrenergic stimuli. Ascorbic acid deficiency in man does not interrupt autonomic reflexes and does not appear to cause significant depletion of endogenous norepinephrine. ※ The abstract text as collected and stored via the API by the pipeline. The key summary is written based solely on this text.

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FDA (openFDA) ASCOR (ascorbic acid injection) - drug label (scurvy indication; oxalate nephropathy and G6PD hemolysis warnings)

This is an institutional information source. Verify directly in the original below.

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USDA FoodData Central Peppers, sweet, red, raw (FDC 170108)