Hey Aedes, today I felt like I was getting a cold, so I took some vitamin C and I'm feeling better.
I don't mean to be a jerk about this, but honestly you have NO idea if 1) you were actually getting a cold, 2) what kind of virus you had (of the MANY different viruses that cause colds), 3) what it would have been like if you had not taken vitamin C, and 4) if you might actually have gotten better faster without
it. Zero idea. Furthermore, you're reporting a subjective diagnosis and a subjective response, and you're already biased towards the result you're reporting. So you'll have to understand that your anecdote is completely meaningless.
There is a reason we do clinical trials that have tens of thousands of patients, in which there are control groups and in which the investigators are blinded to which group was treated.
Were you just saying that it only works for colds and not the flu? You'd think if it boosted the immune system, it would also work for the flu, no?
Absolutely not. You may think that this assumption has logical merit, but if you had a better notion of what the phrase "immune system" actually meant you'd realize that it's a nonsensical conclusion.
There is no such thing as "boosting the immune system".
The immune system isn't just one thing
It is probably the most complex part of the entire human body, there are myriad different cell types and functions, and there are different aspects of it that respond to different viruses. The immune system responds differently to influenza, which is a nonenveloped RNA orthomyxovirus than it does to, for example, adenovirus which is an enveloped double stranded DNA virus that causes very similar illness. And considering the other cold viruses out there (rhinovirus, coronavirus, parainfluenza virus, respiratory syncitial virus, enterovirus, human metapneumovirus, human bocavirus), as well as non-viruses that cause colds (like Mycoplasma pneumoniae and Chlamydia pneumoniae), you CAN'T generalize about a single immune mechanism that controls all these vastly disparate germs.
Quote:This study you cite has not actually been published. It was presented at a meeting, but it does not appear in the medical literature. I'll let you know what I think of the study and its applicability to this discussion if it actually gets accepted to a peer-reviewed journal.
Here's an article I found today on WebMD...
But even so, you cannot draw any conclusion about colds based on their reported methodology and outcomes. Measuring cytokine production is clearly
not an adequate proxy measure for clinical protection against cold viruses.
REAL trials about cold viruses actually take human volunteers and infect them with a standard inoculum of a cold virus. You would need to demonstrate that the subjects did not have measurable IgG, IgA, IgM, or cytotoxic T-cell responses against the virus in question (so that their clinical response would not be modified by pre-existing immunity), you would need to demonstrate that they were functionally immunocompetent (i.e. normal responses to vaccine antigens), and you would need to demonstrate that they were not deficient in vitamin C. And then you would give them all the same inoculum of the same virus, give half vitamin C and half a placebo.
You primary outcome measure would be OBJECTIVE things, like duration of fever, duration of nasal congestion, etc. A secondary outcome would be serum cytokine levels. A tertiary outcome would be subjective symptoms.
Oh, by the way, do not forget that many symptoms of infections are actually produced by the body's inflammatory response to the infection and not by the infectious organism itself. That's why we actually need to give adjunctive immunosuppressants (steroids) for some life-threatening infections like bacterial meningitis and pneumocystis pneumonia (along with antibiotics).
The point is that a higher cytokine level may actually result in a worse
Finally, the thing about science is that there is always more to learn. A high quality trial MAY come along that believably demonstrates that vitamin C is beneficial and not harmful. As of yet such a trial does not exist. And the trials that DO exist are contradicted by other trials, such that a benefit to vitamin C cannot be concluded based on the existing evidence (and there is a LOT of research into this).
This was all pooled together by the Cochrane Database, which takes big topics and reviews the medical evidence. I have full text access through the medical school library. Here is the abstract and summary of the article, which looked at multiple placebo-controlled trials involving something like 11,000 patients. The only group in which vitamin C was beneficial were people exposed to extreme physical stress, but these people may be physiologically and nutritionally different from the normal population, so a result like that cannot be generalized.
Vitamin C for preventing and treating the common coldCochrane Database of Systematic ReviewsDOICochrane Database of Systematic Reviews
2007, Issue 3. Art. No.: CD000980. DOI: 10.1002/14651858.CD000980.pub3.
The role of vitamin C (ascorbic acid) in the prevention and treatment of the common cold has been a subject of controversy for 60 years, but is widely sold and used as both a preventive and therapeutic agent.
To discover whether oral doses of 0.2 g or more daily of vitamin C reduces the incidence, duration or severity of the common cold when used either as continuous prophylaxis or after the onset of symptoms.
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library
Issue 4, 2006); MEDLINE (1966 to December 2006); and EMBASE (1990 to December 2006).
Papers were excluded if a dose less than 0.2 g per day of vitamin C was used, or if there was no placebo comparison.
Data collection and analysis
Two review authors independently extracted data and assessed trial quality. 'Incidence' of colds during prophylaxis was assessed as the proportion of participants experiencing one or more colds during the study period. 'Duration' was the mean days of illness of cold episodes.
Thirty trial comparisons involving 11,350 study participants contributed to the meta-analysis on the relative risk (RR) of developing a cold whilst taking prophylactic vitamin C. The pooled RR was 0.96 (95% confidence intervals (CI) 0.92 to 1.00). A subgroup of six trials involving a total of 642 marathon runners, skiers, and soldiers on sub-arctic exercises reported a pooled RR of 0.50 (95% CI 0.38 to 0.66).
Thirty comparisons involving 9676 respiratory episodes contributed to a meta-analysis on common cold duration during prophylaxis. A consistent benefit was observed, representing a reduction in cold duration of 8% (95% CI 3% to 13%) for adults and 13.6% (95% CI 5% to 22%) for children.
Seven trial comparisons involving 3294 respiratory episodes contributed to the meta-analysis of cold duration during therapy with vitamin C initiated after the onset of symptoms. No significant differences from placebo were seen. Four trial comparisons involving 2753 respiratory episodes contributed to the meta-analysis of cold severity during therapy and no significant differences from placebo were seen.
The failure of vitamin C supplementation to reduce the incidence of colds in the normal population indicates that routine mega-dose prophylaxis is not rationally justified for community use. But evidence suggests that it could be justified in people exposed to brief periods of severe physical exercise or cold environments.
Plain language summary
Vitamin C for preventing and treating the common cold
The term 'the common cold' does not denote a precisely defined disease, yet the characteristics of this illness are familiar to most people. It is a major cause of visits to a doctor in Western countries and of absenteeism from work and school. It is usually caused by respiratory viruses for which antibiotics are useless. Other potential treatment options are of substantial public health interest.
Since vitamin C was isolated in the 1930s it has been proposed for respiratory infections, and became particularly popular in the 1970s for the common cold when (Nobel Prize winner) Linus Pauling drew conclusions from earlier placebo-controlled trials of large dose vitamin C on the incidence of colds. New trials were undertaken.
This review is restricted to placebo-controlled trials testing at least 0.2 g per day of vitamin C. Thirty trials involving 11,350 participants suggest that regular ingestion of vitamin C has no effect on common cold incidence in the ordinary population. It reduced the duration and severity of common cold symptoms slightly, although the magnitude of the effect was so small its clinical usefulness is doubtful. Nevertheless, in six trials with participants exposed to short periods of extreme physical or cold stress or both (including marathon runners and skiers) vitamin C reduced the common cold risk by half.
Trials of high doses of vitamin C administered therapeutically (starting after the onset of symptoms), showed no consistent effect on either duration or severity of symptoms. However, there were only a few therapeutic trials and their quality was variable. One large trial reported equivocal benefit from an 8 g therapeutic dose at the onset of symptoms, and two trials using five-day supplementation reported benefit. More therapeutic trials are necessary to settle the question, especially in children who have not entered these trials.