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 ?
Co-twin control studies: vitamin C and the common cold.
Jtending to make one pair different from another , so providing a more efficient test of the treatment effect . The increase in efficiency of the matched pair over the r and om group design is dependent upon the extent to which the matching has removed extraneous factors influencing the effect of the drug . The ultimate matched pair in human experimentation is a pair of monozygotic ( MZ ) twins who have been reared together . Not only is there a perfect match for age , sex , and family background but , perhaps most importantly , genetic constitution is identical , at least for nuclear genes . The paired and unpaired design s are shown in Table I and have been compared extensively by Christian and Kang [ 1972 ] . The paired analysis allows the partition of variance between individuals ( 0111 ) into that between pairs ( oip ) and that within pairs ( a2 wp ) . For sufficiently large N , if oip > 0 ( ie , if the between-pairs mean square is significantly greater than the pairs x treatments mean square ) , then the paired design will give a more powerful test of the between-treatments effect than the unpaired design . For the num­ bers we have here , it may be shown that oi1/a2 wp is the multiplier to estimate how many more pairs of unrelated individuals would be needed to provide a test of the between-treatments effect of the same power as is provided by a given number of pairs of twins
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 ?