Does Vitamin C Help With Colds?

Does Vitamin C help with colds?

Check out this answer from Consensus:

Vitamin C supplementation does not significantly prevent the common cold in the general population but may be beneficial for individuals under severe physical stress. Regular supplementation can modestly reduce the duration and severity of cold symptoms. However, starting Vitamin C therapy after cold symptoms begin does not consistently show significant benefits. Given its low cost and safety, individuals may consider using Vitamin C to see if it helps them personally. Further research is needed to explore the optimal dosing and timing for therapeutic benefits.

The role of Vitamin C in preventing and treating the common cold has been a subject of scientific investigation and public interest for decades. Numerous studies have explored whether Vitamin C can reduce the incidence, duration, or severity of cold symptoms, with varying results.

Key Insights

• Prevention of Colds:
  • Regular high-dose Vitamin C supplementation does not significantly reduce the incidence of colds in the general population1 2 3 4.
  • However, Vitamin C may reduce the incidence of colds in individuals exposed to severe physical stress or cold environments, such as marathon runners, skiers, and soldiers2 3 4.
• Duration of Cold Symptoms:
  • Regular Vitamin C supplementation can modestly reduce the duration of cold symptoms by about 8% in adults and up to 14% in children1 2 3 4.
  • Extra doses of Vitamin C at the onset of cold symptoms can further reduce the duration of colds5.
• Severity of Cold Symptoms:
  • Regular Vitamin C supplementation can reduce the severity of cold symptoms, including the number of days confined indoors and off work or school2 3 4.
  • Vitamin C supplementation may also alleviate specific symptoms such as chest pain, fever, and chills5 8.
• Therapeutic Use After Onset:
  • Initiating Vitamin C therapy after the onset of cold symptoms does not consistently reduce the duration or severity of colds2 3 4.
  • Some studies suggest that very high doses (e.g., 8 grams) at the onset of symptoms may offer some benefit, but this is not consistently supported2.

Does Vitamin C help with colds?

Peter  McCaffery has answered Unlikely

An expert from University of Aberdeen in Biochemistry

There is little evidence that vitamin C has sufficient effect on colds in the normal population where regular supplementation would not have much of an effect. There may be some cases, as described above, where it may provide a benefit (but certainly a case where more research is needed).

Does Vitamin C help with colds?

Carol  Haggans has answered Unlikely

An expert from National Institutes of Health in Nutrition, Dietetics

For most people, vitamin C supplements don’t reduce the likelihood of coming down with a cold (see https://pubmed.ncbi.nlm.nih.gov/23440782/). However, vitamin C at doses of 250 mg – 1,000 mg/day might help reduce the risk of colds in people exposed to extreme physical stress such as marathon runners, skiers, and soldiers in subarctic areas. Vitamin C supplements might also be helpful in people who get marginal amounts of vitamin C, such as chronic smokers and older adults. In addition, vitamin C supplements taken on a regular basis appear to reduce the duration of the common cold and the severity of its symptoms. But if someone starts taking vitamin C after they come down with a cold, it doesn’t appear to help.

Does Vitamin C help with colds?

Anitra Carr has answered Likely

An expert from University of Otago in Vitamin C

Yes – vitamin C can help with colds. Meta-analysis (comparison of multiple studies) of vitamin C for the prevention and treatment of the common cold has indicated that supplementation with ≥200 mg/d of vitamin C can decrease the duration and severity of the common cold [1, 2]. A handful of studies have also indicated that supplementation with ≥200 mg/d of vitamin C can decrease the risk of getting the common cold by ~50% in people experiencing enhanced physical stress [1]. Research has indicated that vitamin C levels decrease in immune cells during the common cold [3], and supplementation may help improve the vitamin C status of these immune cells [4]. This could potentially improve their immune functions (reviewed in [5]).

References:

1.         Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. The Cochrane database of systematic reviews. 2013;1:CD000980.
2.         Ran L, Zhao W, Wang J, Wang H, Zhao Y, Tseng Y, Bu H. Extra dose of vitamin C based on a daily supplementation shortens the common cold: A meta-analysis of 9 randomized controlled trials. BioMed research international. 2018;2018:1837634.
3.         Hume R, Weyers E. Changes in leucocyte ascorbic acid during the common cold. Scott Med J. 1973;18(1):3-7.
4.         Hunt C, Chakravorty NK, Annan G, Habibzadeh N, Schorah CJ. The clinical effects of vitamin C supplementation in elderly hospitalised patients with acute respiratory infections. Int J Vitam Nutr Res. 1994;64(3):212-9.
5.         Carr AC, Maggini S. Vitamin C and immune function. Nutrients. 2017;9(11):E1211.

Does Vitamin C help with colds?

Margreet Vissers has answered Likely

An expert from University of Otago in Vitamin C, Biochemistry, Cancer Immunology

An optimal vitamin C status is thought to help avoid colds, and do shorten the duration and severity by a little. Most people achieve this through intake of sufficient fruit and vegetables, but many do not.

Does Vitamin C help with colds?

Jens Lykkesfeldt has answered Uncertain

An expert from University of Copenhagen in Pharmacology, Toxicology, Vitamin C

This is a complex question. Most studies within this area are quite old and adequate details can be difficult to obtain. Some evidence suggest that regular vitamin C supplementation can shorten the duration and frequency of common colds while taking vitamin C when you get a cold does not seem to help. However, the effect is limited in individuals that get a balanced diet and are sufficient in vitamin C.

Some studies have shown that there is a larger effect in people that are vitamin C efficient as would be expected. Unfortunately, very few studies have investigated vitamin C supplementation in people with poor vitamin C status. Therefore, we actually don’t know if vitamin C has the potential to alleviate common cold symptoms or reduce frequency of disease – in particular in individuals that do not get enough vitamin C.

Does Vitamin C help with colds?

Harri Hemila has answered Likely

An expert from University of Helsinki in Epidemiology, Nutrition

In evidence-base medicine we are interested in controlled trials. Study participants are divided to two groups equally. One group is administered vitamin C and the other group is the control group which is administered an ineffective placebo.

In controlled trials, vitamin C has not prevented colds in the general community. However, in 31 placebo-controlled studies, regular vitamin C administration reduced common cold duration in adults on average by 8%, and in children by 14%. Based on these 31 studies, there is very strong evidence that vitamin C is better than placebo in alleviating colds.

Vitamin C effects on respiratory viruses

The common cold is a condition that is defined by symptoms; it is caused by over a hundred different respiratory viruses. The distribution of respiratory viruses varies over time and geography. Therefore, the viruses have varied between the dozens of vitamin C trials and it is unlikely that the benefit of vitamin C is explained by an effect on just a certain respiratory virus or virus group. It’s possible that vitamin C also has effects on the new coronavirus, but there is no evidence so far.

How does Vitamin C help?

Infections cause depletion of vitamin C in the body and the benefit of vitamin C for colds seems to be explained by oxidative stress caused by the infection. This explanation has much wider relevance than just the alleviation of cold symptoms.

Critically ill patients have particularly low plasma vitamin C levels, and up to one third of ICU patients have as low vitamin C levels as scurvy patients. Although 0.1 g/day of vitamin C can maintain ordinary plasma levels in healthy persons, critically ill patients need much higher doses (1–4 g/day) to increase plasma vitamin C levels to the ordinary range. We have found Vitamin C to shorten ICU length of stay and duration of mechanical ventilation.

So there are benefits for the “common cold” it is possible that vitamin C has some effects also on the severe forms as it has been beneficial for ICU patients of diverse etiologies. Important role of vitamin C in severe virus infections is supported by a study with mice that found that vitamin C deficiency increased lung pathology caused by influenza A.

Are taking Vitamin C supplements worthwhile?

Given that adults usually have on average 2 colds per year, the 8% effect is quite small when considering vitamin C supplementation for 365 days. Nevertheless, in special conditions regular supplementation can be reasonable for the purpose of alleviating respiratory virus infections.

For example, when someone frequently suffers from colds, regular vitamin C might be worth trying. In addition, when there is a pandemic virus such as the new coronavirus which often causes severe illness, it may be reasonable to take vitamin C regularly while the pandemic is ongoing. We do not know whether the 8% estimate applies to the new coronavirus, but also we cannot wait for studies intended to find out an answer to such a specific question.

Daily intake needed?

The average dose of vitamin C has been 1 g/day in the 31 controlled trials and it does not seem reasonable to take higher doses when one is in good health. However, during the common colds, 6-8 g/day of vitamin C has been found to be more beneficial than 3-4 g/day. We do not know if even higher doses might be still more effective when a person suffers from a respiratory virus infection.

The Origins of Vitamin C Skepticism

Given that there is very strong evidence that vitamin C has effects on colds, why do most physicians believe that vitamin C is ineffective? Two highly influential reviews on vitamin C and the common cold were published in 1975 and both of them were negative. They explain why the interest in vitamin C vanished in the late 1970s. They have been standard textbook references when authors have claimed that vitamin C has no effects on colds. However, both reviews are flawed in which we have explained in the literature here and here. Thus, the belief that vitamin C has no effects on colds is not explained by negative findings from randomized placebo-controlled trials, but by preconceptions against vitamin C, and by those two misleading reviews by eminent authors.

Practical questions remain open

Although placebo-controlled trials have unambiguously shown that regularly administered vitamin C is better than placebo for alleviating the common cold, the practical significance is still an open question and further research is needed. We do not know what is the best dose and how much benefit we would get from the best dosages.