title: Vitamin C as a preventive medicine against common colds in children. Vitamin C prophylaxis in marine recruits. Preventing the common cold with a vitamin C supplement: A double-blind, placebo-controlled survey Vitamin C and the common cold: a double-blind trial. The effect of vitamin C on upper respiratory infections in adolescent swimmers: a randomized trial The effect on winter illness of large doses of vitamin C. Winter illness and vitamin C: the effect of relatively low doses.
abstract: During 7 weeks in the spring of 1973 a double-blind pilot study on 172 children in the age group 8 - 9 was carried out to test the possible effect of 1000 mg vitamin C daily as a prophylactic agent against common colds . During the autumn of 1973 , a main study was carried out on 642 children of the same age . The investigations had the same pattern and lasted for 3 months . Both studies have been processed on the same principles . The results were somewhat divergent but , like previously published studies on children , seemed to indicate that the duration and severity of the cold were reduced while , on the other h and , the incidence remained unaltered or indeed increased . The total number of days of upper respiratory tract infection was smaller for the vitamin C group only in the pilot study ( not in the main study ) . No proven biochemical effects were obtained . Preventive treatment of healthy children with vitamin C in large doses this had no definitely proved effect against colds A prospect i ve , r and omized , double-blind study was carried out to determine whether vitamin C prophylaxis , 2.0 g/day , vs placebo prophylaxis would reduce the incidence or morbidity of the common cold  and other respiratory illnesses in 674 marine recruits during an eight-week period . Whole-blood ascorbic acid levels measured six weeks after initiation of the study were significantly higher in the vitamin C group . There was no difference between the two groups in the incidence or duration of colds . The vitamin C group rated their colds as being less severe , but this was not reflected in different symptom complexes or in fewer sick-call visits or training days lost . This study and the literature do not support the prophylactic use of vitamin C to prevent the common cold One hundred sixty-eight volunteers were r and omized to receive a placebo or a vitamin C supplement , two tablets daily , over a 60-day period between November and February . They used a five-point scale to assess their health and recorded any common cold infections and symptoms in a daily diary . Compared with the placebo group , the active-treatment group had significantly fewer colds ( 37 vs 50 , P<.05 ) , fewer days challenged virally ( 85 vs 178 ) , and a significantly shorter duration of severe symptoms ( 1.8 vs 3.1 days , P<.03 ) . Consequently , volunteers in the active group were less likely to get a cold and recovered faster if infected . Few side effects occurred with the active treatment , and volunteers reported greatly increased satisfaction with the study supplement compared with any previous form of vitamin C. This well-tolerated vitamin C supplement may prevent the common cold and shorten the duration of symptoms . Volunteers were generally impressed by the protection afforded them during the winter months and the general acceptability of the study medication A large scale double-blind trial was conducted to test the cl aim that the intake of one gram of vitamin C per day substantially reduces the frequency and duration of " colds " . It was found that in terms of the average number of colds and days of sickness per subject the vitamin group experienced less illness than the placebo group , but the differences were smaller than have been cl aim ed and were statistically not significant . However , there was a statistically significant difference ( P < 0.05 ) between the two groups in the number of subjects who remained free of illness throughout the study period . Furthermore the subjects receiving the vitamin experienced approximately 30 % fewer total days of disability ( confined to the house or off work ) than those receiving the placebo , and this difference was statistically highly significant ( P < 0.001 ) . The reduction in disability appeared to be due to a lower incidence of constitutional symptoms such as chills and severe malaise , and was seen in all types of acute illness , including those which did not involve the upper respiratory tract The risk of upper respiratory infections ( URIs ) is increased in people who are under heavy physical stress , including recreational and competitive swimmers . Additional treatment options are needed , especially in the younger age group . The aim of this study was to determine whether 1 g/day vitamin C supplementation affects the rate , length , or severity of URIs in adolescent swimmers . We carried out a r and omized , double-blind , placebo-controlled trial during three winter months , among 39 competitive young swimmers ( mean age 13.8 ± 1.6 years ) in Jerusalem , Israel .  Vitamin C had no effect on the incidence of URIs ( rate ratio = 1.01 ; 95 % confidence interval ( CI ) = 0.70–1.46 ) . The duration of respiratory infections was 22 % shorter in vitamin C group , but the difference was not statistically significant . However , we found a significant interaction between vitamin C effect and sex , so that vitamin C shortened the duration of infections in male swimmers by 47 % ( 95 % CI : −80 % to −14 % ) , but had no effect on female swimmers ( difference in duration : + 17 % ; 95 % CI : −38 % to + 71 % ) . The effect of vitamin C on the severity of URIs was also different between male and female swimmers , so that vitamin C was beneficial for males , but not for females . Our study indicates that vitamin C does not affect the rate of respiratory infections in competitive swimmers . Nevertheless , we found that vitamin C  decreased the duration and severity of respiratory infections in male swimmers , but not in females . This finding warrants further research Between December 1972 and February 1973 , 2349 volunteers participated in a double-blind trial to assess the effect of large doses of vitamin C on the  incidence and severity of winter illness .  In addition , records were kept but no tablets taken during March . Subjects were r and omly allocated to eight treatment regimens : three prophylactic-only ( daily dose 0.25 , 1 or 2 g ) , two therapeutic-only ( 4 or 8 g on the first day of illness ) , one combination ( 1 g daily and 4 g on the first day of illness ) , and two all-placebo . None of the groups receiving vitamin C showed a difference in sickness experience that was statistically significant from that of the placebo groups , but the results obtained were compatible with an effect of small magnitude from both the prophylactic and therapeutic regimens , and an effect of somewhat greater magnitude from the combination regimen . The combination regimen was associated more with a reduction in severity than frequency of illness , although the extra dosage was limited to the first day of illness . In spite of the eightfold range in daily dose , the three prophylactic-only regimens showed no evidence of a dose-related effect , but the 8 g therapeutic dose was associated with less illness than the 4 g therapeutic dose . There was no evidence of side effects from the 1 and 2 g prophylactic doses of vitamin C , and no evidence of a rebound increase in illness during the month following withdrawal of the daily vitamin supplements . On the basis of this and other studies it is suggested that the optimum daily dose of vitamin C is less than 250 mg , except possibly at the time of acute illness , when a larger daily intake may be beneficial After their r and om -llocation to one of three treatment aroups , 622 volunteers received either  vitamin C or placebo in a maintenance dose of 500 mg once weekly and a therapeutic dose of 1500 mg daily on the 1st day and 1000 mg on the next 4 days of any illness . Two forms of vitamin C were employed : a sustained-release capsule containing ascorbic acid and a regular tabet containing a mixture of sodium and calcium ascorbate . In the 448 subjects who completed an average of 15 weeks in the study of total of 635 episodes of illness were recroded . Respiratory symptoms were recorded on at least 1 day in 92 per cent of these episodes . There were no consistent or significant differences in the sickness experience of the subjects receiving the sustained-release vitamin capsules compared to those receiving the vitamin tablets , but subjects in both vitamin groups experienced less severe illness than subjects in the placebo group , with approximately 25 per cent fewer days spent indoors because of the illness ( P smaller than 0.05 ) . These results are compatible with the belief that supplementary vitamin C can reduce the burden of winter illness , but the intake need not be as high as has sometimes been cl aim ed
target: In addition , numerous trials have shown no difference regarding the most commonly studied endpoint : frequency of symptoms .
  In 5 trials with participants under heavy acute physical stress ( 3 with marathon runners )  , vitamin C  reduced the incidence of colds by 52 % ( 95 % CI : 36 % to 65 % ) , but there is no evidence that vitamin C prevents colds in the general population .
background: Proponents of evidence -based medicine ( EBM ) emphasize that conclusions about medical interventions should be based on controlled trials with clinical ly relevant outcomes , so that the greatest weight should be given to the systematic review s of the trials .
  So far , therapeutic supplementation has not been shown to be effective .