Vitamin C in doses as high as one gram daily for several winter months , had no consistent beneficial effect on incidence of the common cold .
For both preventive and therapeutic trials , there was a consistently beneficial but generally modest therapeutic effect on duration of cold symptoms .
There was no clear indication of the relative benefits of different regimes or vitamin C doses .
However in trials that tested vitamin C after cold symptoms occurred , there was some evidence that a large dose produced greater benefits than lower doses .
REVIEW ER 'S CONCLUSIONS Long term daily supplementation with vitamin C in large doses daily does not appear to prevent colds .
BACKGROUND The role of oral ascorbic acid ( vitamin C ) in the prevention and treatment of colds remains controversial despite many controlled trials .
There have also been a number of efforts to synthesize and /or overview the results of these trials , and controversy over what these overviews tell us .
OBJECTIVES The objective of this review was to answer the following two questions : ( 1 ) Does regular high dosage supplementation with vitamin C reduce the incidence of colds ? (
2 ) Does taking vitamin C in high doses at the onset of a cold have a therapeutic effect ?
A Randomized Controlled Trial for Chemoprevention of Gastric Cancer in High‐risk Japanese Population; Study Design, Feasibility and Protocol Modification
We have initiated a population ‐based , double‐blind , r and omized controlled trial to examine the effects of supplementation of beta‐carotene and vitamin C on the incidence of  gastric cancer . The subjects were participants in an annual health screening program conducted by four municipalities in Akita prefecture , one of the regions with the highest mortality from gastric cancer in Japan . We measured their serum levels of pepsinogens ( PGs ) I and II , and asked persons diagnosed with chronic atrophic gastritis ( defined as PGI < 70 ng/ml and PGI/PGII ratio < 3.0 ) to take diet supplements containing 0 or 15 mg/day beta‐carotene and 50 or 500 mg/day vitamin C for 5 years . During the first year of recruitment conducted in one village from June through September , 1995 , 52 % ( 635/1214 ) of screening participants had chronic atrophic gastritis and 73 % ( 439/602 ) of eligible persons responded . However , in response to a National Cancer Institute press report released on January 18 , 1996 , indicating that two beta‐carotene trials had shown no benefit and potential harm from the supplement , we discontinued the beta‐carotene and continued with the trial using only vitamin C.  Of 397 participants remaining at this point , 77 % ( 305 ) consented to stay in the study . The results indicate that a r and omized controlled trial for cancer prevention is feasible in the Japanese asymptomatic population
Vitamin C in doses as high as one gram daily for several winter months , had no consistent beneficial effect on incidence of the common cold .
For both preventive and therapeutic trials , there was a consistently beneficial but generally modest therapeutic effect on duration of cold symptoms .
There was no clear indication of the relative benefits of different regimes or vitamin C doses .
However in trials that tested vitamin C after cold symptoms occurred , there was some evidence that a large dose produced greater benefits than lower doses .
REVIEW ER 'S CONCLUSIONS Long term daily supplementation with vitamin C in large doses daily does not appear to prevent colds .
BACKGROUND The role of oral ascorbic acid ( vitamin C ) in the prevention and treatment of colds remains controversial despite many controlled trials .
There have also been a number of efforts to synthesize and /or overview the results of these trials , and controversy over what these overviews tell us .
OBJECTIVES The objective of this review was to answer the following two questions : ( 1 ) Does regular high dosage supplementation with vitamin C reduce the incidence of colds ? (
2 ) Does taking vitamin C in high doses at the onset of a cold have a therapeutic effect ?