19 July 2007

Vitamin C Does NOT Prevent Colds

Linus Pauling will frown on this if he was alive today. After all, he used to take anywhere between 6 grams to 18 grams of Vitamin C per day. Yes, that much! The World Health Organization puts it at 45 milligrams per day as its recommended daily intake, while the US RDA pegs it at 90mgs/day for males and 75mgs/day for females. Anything beyond those recommended daily doses can already qualify for the term, "megadosing on Vitamin C".

The latest report on Vitamin C comes the Cochrane Library which is known for its analytical and systematic reviews of published medical studies:
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.


[The Cochrane Library, 18 July 2007]

How much Vitamin C are you taking everyday? In your experience, is it preventing you to have colds or is it just an illusionary security blanket you would like to keep? Better yet, why not consume the real stuff instead? You know, oranges, calamansi juice, ponkan, kiwi fruits, etc.

BOTTOMLINE: The recent study says taking Vitamin C daily will not shield you from having colds, but if you already have cold-like symptoms, your duration of illness may be cut short (although that remains doubtful because the degree of therapeutic benefit was "so small" and test subjects were limited to marathon runners and skiers only).

4 reactions:

xingkit said...

hmm, doc, i take 500mgs a day, and whenever i miss taking one, feeling ko magkakasakit ako. psychological effect? : )

may said...

but the mind works more powerfully than the vitamin c. when you take it, you believe it will prevent colds...by mental suggestion, it happens :)

Dr. Emer said...

XINGKIT and MAY: That is called the placebo effect. It is not really the Vitamin C tablet protecting you, but your mind telling your body to strengthen its defenses (immune system).

ipanema said...

i've stopped taking Vit. C supplements for 4 years now. i found out that eating 2-3 oranges a day is more effective for my family that is.

yes, i believe that taking Vit. C is not a shield against colds just as my eating oranges is.