Abstract Vitamin C
Proponents of evidence-based medicine emphasize that conclusions about the effects of interventions should be based on controlled trials with clinically relevant outcomes, and not on studies measuring laboratory markers or on epidemiological studies. Studies with laboratory outcomes are often unreli...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.414.1299 http://www.mv.helsinki.fi/home/hemila/H/HH_2010_Korea_Eng_ch.pdf |
| Summary: | Proponents of evidence-based medicine emphasize that conclusions about the effects of interventions should be based on controlled trials with clinically relevant outcomes, and not on studies measuring laboratory markers or on epidemiological studies. Studies with laboratory outcomes are often unreliable because the effects on surrogate outcomes (e.g. measurements of laboratory markers of the immune system) can substantially differ from the effects on clinically relevant outcomes. Epidemiological studies often measure clinically relevant outcomes, but unknown differences between the study groups could explain the observed differences in the outcome. Therefore, my work on vitamin C has focused on controlled trials with clinically relevant outcomes. In our systematic review on vitamin C supplementation and the common cold (1), we combined the results of 24 trial comparisons involving 10,708 participants of the general community who had been administered prophylactically �0.2 g/day of vitamin C. The pooled risk ratio (RR) of colds, RR=0.97 (95 % Cl: 0.94 to 1.00), indicates that there is no evidence that regular vitamin C supplementation might reduce the risk of colds in the general community. However, five trials involving a total of 598 marathon runners, skiers, and soldiers on sub-arctic exercises yielded a pooled RR = 0.48 (0.35 to 0.64) for common cold incidence, indicating benefit for such people. Thus, there may be substantial heterogeneity in the effect of vitamin |
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