lunes, 23 de julio de 2007

La Vitamina C y la prevención del Catarro Común

Llevamos toda la vida escuchando lo buena que era la vitamina C para prevenir el catarro. Gracias a las investigaciones del Dr. Linus Pauling en 1970, la popularidad de la vitamina C fue imparable. La dosis necesaria para evitar el catarro común eran 1000 miligramos al día.
Se han publicado numerosas investigaciones que desmontaban ese mito, pero ahora la Cochrane ha publicado una revisión concluyente:
Douglas RM, Hemilä H, Chalker E, Treacy B. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews 2007, Issue 3.

Aquí tenéis el resumen en inglés:
This Cochrane review found that taking vitamin C regularly has no effect on common cold incidence in the ordinary population.
It reduced the duration and severity of common cold symptoms slightly, although the size of the effect was so small its clinical usefulness is uncertain. The authors investigated 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. The review included studies using a vitamin C dose of greater than 0.2g per day and those with a placebo comparison.
• For the prophylaxis of colds, the authors carried out a meta-analysis of 30 trials comparisons involving 11,350 study participants. The pooled relative risk (RR) of developing a cold whilst taking prophylactic vitamin C was 0.96 (95% confidence intervals (CI) 0.92 to 1.00). However, 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) i.e. a 50% reduction in the risk of a cold for this group of people.• For the duration of the common cold during prophylaxis, the authors carried out a meta-analysis using 30 comparisons involving 9676 respiratory episodes. They found a consistent benefit with a reduction in cold duration of 8% (95% CI 3% to 13%) for adults and 13.6% (95% CI 5% to 22%) for children.• For the duration of cold during therapy with vitamin C started after symptom onset, the authors carried out a meta-analysis of 7 trials involving 3294 respiratory episodes. No significant differences from placebo were seen.• No significant differences were seen in a meta analysis of 4 trial comparisons involving 2753 respiratory episodes in cold severity during therapy with vitamin C.
The authors conclude, “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.”

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