The beneficial effect of Vitamin C on the common cold Common cold and vitamin C. A controlled clinical trial of ascorbic acid for the common cold. Vitamin C prophylaxis in marine recruits. The administration of large doses of ascorbic acid in the prevention and treatment of the common cold. II. Mega-dose vitamin C in treatment of the common cold: a randomised controlled trial. Evaluation of the efficacy of ascorbic acid in prophylaxis of induced rhinovirus 44 infection in man. Trial of ascorbic acid in prevention of colds. Vitamin C as a preventive medicine against common colds in children. Preventing the common cold with a vitamin C supplement: A double-blind, placebo-controlled survey A randomized controlled trial of vitamin C in the prevention and amelioration of the common cold. Common cold symptomatology and Vitamin C The prophylactic and therapeutic effectiveness of zinc sulphate on common cold in children Vitamin C and acute illness in Navajo school children. The effects of ascorbic acid and flavonoids on the occurrence of symptoms normally associated with the common cold. Vitamin C and upper respiratory illness in Navaho children: preliminary observations (1974). Ascorbic acid for the common cold. A prophylactic and therapeutic trial. Effect of a dietary supplement containing probiotic bacteria plus vitamins and minerals on common cold infections and cellular immune parameters.
Summary The occurrence of common cold symptoms was recorded daily for a period of nine months by children from two male and two female boarding schools . All the children in one male and one female school received tablets containing 200 mg Vitamin C , or placebo tablets , daily on a double blind basis . Children in the other two schools received 200 or 500 mg tablets of Vitamin C.  Leucocyte ascorbic acid concentrations were significantly raised in those children receiving active tablets . Comparisons of incidence , duration , severity and total intensity of cold characteristics , and of cold frequencies , were made between the different treatment groups . Cold symptoms were grouped into those characteristic of Catarrhal ( C-colds ) , and those of Toxic ( T-colds ) , colds . Whole ( W-colds ) consisted of at least one C-symptom in combination with one or more T-symptoms . 200 mg of Vitamin C had a beneficial effect on severity and total intensity of C- and W-colds , but did not affect T-colds , in girls . 500 mg produced further slight beneficial effects . With 200 mg the cold categories in boys tended to show a deterioration , and the deterioration continued in the group receiving 500 mg . Analysis of cold frequency indicated that T-colds are commoner in girls . Their C-cold frequency diminished with the smaller dose , and their T-cold frequency was reduced by the larger dose of Vitamin C. In boys C-cold frequency diminished with 500 mg of Vitamin C daily . These data suggest that there is a sexual difference in the effects of Vitamin C on the characteristics of the common cold . Evaluation of the effects of Vitamin C on toxic and catarrhal symptoms in relation to administered doses is of more importance than examination of its prophylactic or therapeutic actions . 500 mg had some beneficial effect in girls : any beneficial effect of Vitamin C on the common cold in boys will probably be associated with administration of a higher daily dose Abstract The effect of daily administration of placebo or 200 or 500 mg . tablets of vitamin C on symptom association and on the incidence , duration , severity , and total intensity of the symptoms  in the common cold has been studied . The metabolism of ascorbic acid during the common cold , and after disappearance of all the symptoms , has been investigated by examining the plasma and leucocyte ascorbic-acid concentrations after a loading dose of 500 mg . vitamin C. Cold symptoms tend to dissociate into toxic and catarrhal complexes , the complexity and frequency of which differ between boys and girls .  Vitamin C reduces symptom association and alters the frequency of toxic and catarrhal complexes . It significantly reduces the severity and total intensity of colds in girls , but does not benefit cold symptoms in boys at a daily dose of 500 mg . During colds , especially of the catarrhal variety , ascorbic acid is transferred out of the leucocytes into the plasma , where it is rapidly metabolised in both sexes , but this effect is more pronounced in females . There is a significant positive correlation between metabolic utilisation of ascorbic acid during colds and intensity of cold symptoms Vitamin C has been a popular medication for preventing the common cold and reducing the severity of cold symptoms for many years . - ' Professor Pauling 's recent book on the subject has led to even further use of vitamin C in even larger doses . This study was performed to look for a difference in the frequency and severity of colds in a generally healthy , middle-class , medically aware population of employees at the National Institutes of Health . High doses of vitamin C were used for both prevention and treatment ; virus isolations were attempted in an effort to relate viral types to vitamin C response ; and the study was continued for a nine-month period in an attempt to examine seasonal variations of viruses and colds . The study was conducted so that nurses , physicians , and volunteers did not know who received placebo and who received ascorbic acid . Only the consulting statistician and the pharmacist could relate patient code numbers to medication received . Progress was monitored by a research committee not connected with the day-to-day activities 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 Beginning at about the age of seven and following a tonsillectomy I began to be plagued with otitis media of which I suffered from 50 to 60 bouts over the next 20 years . These recurrent infections were treated by a series of different methods including Cubeb cigarette smoke blown into the ear by my mother , the local application of heat , sulfadiazine in nasal sprays and the earlier and later forms of injected penicillin which was useful as soon as I suffered from a sore throat if taken at the first signs of infection , but only for the secondary bacterial component of my double infection which began with a vims which appeared to pass the sentence which was executed by the bacteria . I stumbled upon the employment of ascorbic acid because of the advertisements for the bioflavonoids and vitamin C as beneficial in the prevention - and treatment of the common cold . It was apparent that the mixture diminished the symptoms of the common cold for me and for my wife , but not enough for us to continue with its employment , Would larger doses perhaps be more effective ? The doses were increased as each increment proved itself as giving better results until I reached a maximum and satisfactory effect . I did not permit myself to be dissuaded by the gloomy conclusions of others , whose work I continued to recognize had shown only that vitamin C had not been helpful against colds at the dosage used in their studies , and not the unmeasured generality that this drug had been proven utterly useless against colds . I was then able to suppress colds , at will , in five subjects . There is no doubt that we really suffered from colds during these suppressed versions of the disease , because we continued to be aware — but just aware — of whatever symptoms had been characteristic of our formerly unmodified colds . Although running of the nose would be practically non-existent , on rare occasions a single drop might appear at the nares ; however , not -a trace of " itchiness " had accompanied it in its roll down the turbinates . The thickened stage of nasal discharge was never reached . Sneezing and coughing were quite unusual . A throat did not proceed to " soreness " but , in some cases , there was a slight sensation of its presence . Hoarseness was uncommon . Headache was inconsequential . Malaise , if at all recognizable was usually so minor as to be undeserving of the name . Secondary bacterial invasions did not occur . I learned that the treatment had to be initiated early enough and needed to be continued at a high level for some time and then withdrawn or OBJECTIVE To determine the effect of large doses of vitamin C in the treatment of the common cold . STUDY DESIGN Double-blind , r and omised clinical trial with four intervention arms : vitamin C at daily doses of 0.03 g ( " placebo " ) , 1 g , 3 g , or 3 g with additives ( " Bio-C " ) taken at onset of a cold and for the following two days . PARTICIPANTS AND SETTING 400 healthy volunteers were recruited from staff and students of the Australian National University , Canberra , ACT , between May 1998 and November 1999 . The trial continued for 18 months . INTERVENTIONS Participants were instructed to commence medication when they had experienced early symptoms of a cold for four hours , and to record daily their symptoms , severity , doctor visits and use of other medications . MAIN OUTCOME MEASURES Duration of symptoms and cold episodes ; cumulative symptom severity scores after 7 , 14 and 28 days ; doctor visits ; and whether participants guessed which medication they were taking . RESULTS 149 participants returned records for 184 cold episodes . No significant differences were observed in any measure of cold duration or severity between the four medication groups . Although differences were not significant , the placebo group had the shortest duration of nasal , systemic and overall symptoms , and the lowest mean severity score at 14 days , and the second lowest at 7 and 28 days . CONCLUSIONS Doses of vitamin C in excess of 1 g daily taken shortly after onset of a cold did not reduce the duration or severity of cold symptoms in healthy adult volunteers when compared with a vitamin C dose less than the minimum recommended daily intake Twenty-one healthy , susceptible adult male volunteers were enrolled in a doubleblind study design ed for evaluation of the prophylactic efficacy of ascorbic acid ( 3 g daily ) in induced rhinovirus 44 infection of the upper respiratory tract . While in continuous isolation , 11 men received 1 g of ascorbic acid three times daily , and 10 men received a placebo for two weeks , after which an intranasal inoculum containing 100 TCID50 of rhinovirus 44 was administered . Each man continued to receive the same dose of medication for one week after the viral challenge . All participants subsequently developed typical illness due to rhinovirus . Similar levels of antibody in serum , nasal washings , and sputum developed in all subjects . Nasal shedding of virus and the flow of the nasal mucociliary blanket were unaffected by the ingestion of ascorbic acid . No prophylactic benefit was demonstrated from the daily ingestion of 3 g of ascorbic acid in induced rhinovirus 44 infection in man . Viral infections of the respiratory tract are the most common illness affecting mankind . The mortality from these afflictions is low , but the morbidity , when assessed as discomfort and time lost from gainful employment and leisure pursuits , is high . Therefore , it is critical to assess the controversial cl aims for the efficacy of ascorbic acid ( vitamin C ) for the prevention and relief of colds [ 1 - 5 ] . The need for a further study of the possible role of ascorbic acid in the prophylaxis and therapy of viral infections of the respiratory tract under carefully controlled circumstances was evident Ascorbic acid is widely used as a prophylactic and therapeutic agent against the common cold , and is in fact often recommended for this purpose by medical practitioners . It may be administered as a large dose as soon as possible after the first symptoms are felt , and this dosage is then continued for a few days in order to " abort " the cold . Though many people use this treatment on themselves and believe it is effective , it is impossible to assess its efficacy . Untreated subjects may experience symptoms such as sneezing or a mild sore throat , which then disappear without going on to a full cold , and patients ' assessment s of their colds are much influenced by any treatment owing to the placebo effect ( Diehl et a/. , 1938 ) . In these studies we attempted to show by in-vitro experiments that exposure of cells to ascorbic acid increased their resistance to infection with viruses . Though there was no activity in vitro , we also attempted to demonstrate a protective effect in ftnmy»1 « or man , since it was thought that host resistance might be enhanced indirectly 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 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 r and omized controlled trial of the effect of 1 g ascorbic acid per day in the prevention of the common cold was conducted on 688 adult women . There is evidence of a small reduction by  vitamin C  in the mean number of chest colds , but no evidence of any effect on simple colds . The existence of a subgroup of vulnerable women in the community who benefit from vitamin C was considered but further examination of the data gives no support to this conclusion Summary The occurrence and severity of nine symptoms of the common cold were recorded daily for 35 weeks by girls and boys in four Dublin boarding schools . Half the children in each school received placebo or 200 mg tablets , or 200 mg or 500 mg tablets , of Vitamin C daily on a double blind basis . Diets or environmental conditions did not differ between the schools . A score for the severity of each symptom was obtained daily for all the subjects throughout the trial in the different treatment groups . The degree of association between pairs of symptoms was calculated . The symptoms of the common cold syndrome ( the W-complex ) tended to exist in two groups defined as Toxic and Catarrhal complexes ( T- and C-complexes ) . The intensity and quality of W-complex symptoms were assessed in terms of the correlation value above which the constituent T- and C-complexes became manifest , the average correlation values of the constituent complexes , and the linkage of the symptoms in these complexes . The values for , and quality of , the complexes were dependent on the sex of the sample s and the dose of Vitamin C administered . Boys tended to have more complicated W-complexes which broke down into T- and C-complexes with the lower dose of Vitamin C. These became more complicated when increasing doses of Vitamin C were administered . Girls had less complicated W-complexes , but more complicated T- and C-complexes , than boys . Increasing doses of Vitamin C made the girls ' T- and C-complexes less complicated . Administration of Vitamin C appeared to benefit the common cold syndrome more in girls than in boys Aim : To determine the efficacy of prophylactic administration of zinc sulphate in reducing the occurrence of the common cold in children , and to evaluate the efficacy of zinc sulphate in reducing the duration and severity of cold symptoms . Methods : A total of 200 healthy children were r and omly assigned to receive oral zinc sulphate ( zinc group , n=100 ) or placebo ( placebo group , n=100 ) . Zinc sulphate ( 15 mg of zinc ) or placebo syrup were administered for prophylaxis once daily during a 7‐mo study period . The dose was increased to two times per day ( 30 mg of zinc ) at the onset of cold , until symptoms resolved . Results : The mean number of colds in the zinc group was significantly less than in the placebo group ( 1.2 vs 1.7 colds per child ; p=0.003 ) . The mean cold‐related school absence was 0.9 d per child in the zinc group versus 1.3 d in the placebo group ( p=0.04 ) . Compared to the placebo group , the zinc group had shorter mean duration of cold symptoms and decreased total severity scores for cold symptoms ( p<0.0001 ) . Adverse effects were mild and similar in both groups To evaluate earlier observations , including our own , showing usefulness of vitamin C for managing the common cold , we performed a double-blind trial of vitamin C versus placebo in 868 children . There was no difference in number becoming ill ( 133 versus 129 ) , number of episodes ( 166 versus 159 ) or mean illness duration ( 5.5 versus 5.8 days ) between the groups . Children receiving vitamin C  had fewer throat cultures yielding beta-hemolytic streptococcus ( six versus 13 , P less than 0.10 ) , but no difference in overall complicated illness rate ( 24 versus 25 ) . Plasma ascorbic acid levels were higher in the vitamin group 24 to 26 hours after supplementation ( 1.28 versus 1.04 mg per 100 ml , P less than 0.01 ) . Children with high plasma ascorbic acid concentrations had longer mean illness ( 6.8 versus 4.0 days , P less than 0.05 ) than those with low levels . Vitamin C does not seem to be an effective prophylactic or therapeutic agent for upper respiratory illness A controlled study was made of the effects of natural orange juice , synthetic orange juice , and placebo in the prevention of the common cold ; both natural and synthetic orange juices contained 80 mg of ascorbic acid daily . Three-hundred sixty-two healthy normal young adult volunteers , ages 17 to 25 years , were studied for 72 days with 97 % of participants completing the trial . There was a 14 to 21 % reduction in total symptoms due to the common cold in the supplemented groups that was statistically significant ( P less than 0.05 ) . Ascorbic acid supplementation also increased the number of " episode-free " subjects . However , the clinical usefulness of the results does not support prophylactic ascorbic acid supplements in the well-nourished adult . The results in this study with both natural and synthetic orange juice of physiological content of ascorbic acid , are similar to those obtained using a " megadose " of ascorbic acid In a large double-blind study among Navaho school children , we evaluated the effects of vitamin C in 1- and 2-gram daily doses on acute respiratory illness during a 14-week period . ' We found no evidence of significant prophylaxis , but our findings did suggest a modest therapeutic benefit in that children taking vitamin Chad from 28 % to 34 % fewer days of morbidity caused by respiratory episodes than those taking placebo . Likewise , in classroom surveillance , younger children on vitamin C had 26 % fewer symptom-days of cough and nasal discharge recorded . These observations were consistent with other recent trials using 1 gram daily ( 4 grams during illness ) in Canadian adults L ' and 250 - 500 milligrams daily in Irish schoolchildren.3 The clinical significance of this modest therapeutic result in minor , selflimited illness was , in itself , question able . However , further study was indicated to determine : ( a ) if use of vitamin C could prevent complications of the common cold in children , such as superinfections or otitis media ; ( b ) if certain symptoms or symptom complexes responded specifically to vitamin C therapy ; and ( c ) if indeed , as our data had suggested , l higher blood ascorbic acid levels were correlated with fewer days of illness . A second investigation was design ed to confirm , if possible , and exp and our previous findings . The second trial was conducted in two Navaho boarding schools during January through May 1974 , using doses of 1 gram vitamin C daily versus placebo tablets . This report presents preliminary routine surveillance findings from the second study Three hundred eleven employees of the National Institutes of Health volunteered to take 1 gm of ascorbic acid or lactose placebo in capsules three times a day for nine months . At the onset of a cold , the volunteers were given an additional 3 gm daily of either a placebo or ascorbic acid .  One hundred ninety volunteers completed the study . Dropouts were defined as those who missed at least one month of drug ingestion . They represented 44 % of the placebo group and 34 % of those taking ascorbic acid . Analysis of these data showed that ascorbic acid had at best only a minor influence on the duration and severity of colds , and that the effects demonstrated might be explained equally well by a break in the double blind OBJECTIVE A r and omized , double-blind , placebo-controlled intervention study was carried out in order to investigate whether consumption of a dietary supplement containing probiotic bacteria plus vitamins and minerals over a period of at least three months in winter/spring affects the duration , frequency , and severity of symptoms of naturally acquired common cold infections as well as cellular immune parameters . METHODS 477 healthy men and women ( aged 36 + /- 13 , mean + /- SD ) who had not been vaccinated against influenza were r and omly assigned to a group who received daily the probiotic multivitamin and mineral supplement ( verum ) or a placebo , for three ( n = 239 ) or for 5.5 months ( n = 238 ) . Cellular immune response was determined in 60 participants per study group by flow cytometry before and after 14 days of supplementation . RESULTS The incidence of respiratory tract infections regarded as being virally induced was 13.6 % lower in the verum group compared to the placebo group ( p = 0.07 ) . During respiratory tract infection episodes , the subjects recorded common cold and influenza-like symptoms daily . All symptoms were reduced in the verum group . We found a relative reduction of 19 % in the total symptom score ( p = 0.12 ) , 25 % in influenza symptoms ( p = 0.09 ) , and 54 % in the number of days with fever ( p = 0.03 ) . The duration of these infections was not affected . Leukocytes , lymphocytes , in particular T-lymphocytes including CD4 + and CD8 + cells , as well as monocytes were significantly higher increased in the verum group , during the first 14 days of supplementation compared to placebo . CONCLUSION These data indicate that the intake of a dietary supplement containing probiotic bacteria plus vitamins and minerals during a period of at least three months in winter/spring may reduce the incidence and the severity of symptoms in common cold infections in otherwise healthy adults . This may be due to stimulated cellular immunity
REVIEW ERS ' CONCLUSIONS 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 shows that it could be justified in persons exposed to brief periods of severe physical exercise and /or cold environments .
Also , the consistent and statistically significant small benefits on duration and severity for those using regular vitamin C prophylaxis indicates that vitamin C plays some role in respiratory defence mechanisms .
BACKGROUND The role of oral vitamin C ( ascorbic acid ) in the prevention and treatment of the  common cold  has been a subject of controversy for at least sixty years .
Public interest in the topic continues to be high and vitamin C continues to be widely sold and used as a preventive and therapeutic agent for this common ailment .
OBJECTIVES To discover whether oral vitamin C in doses of 200 mg or more daily , reduces the incidence , duration or severity of the common cold when used either as continuous prophylaxis or after the onset of cold symptoms .