Table 1.

Characteristics of included trials

Trial [ref] Country	Participants	Age mean (y)	Number of colds	Vitamin C dose (g/day)	Duration of the trial (months)
Ludvigsson (1977 L) [30] Sweden	Schoolchildren	9	1279	1	3
Pitt (1979) [41] USA	Marine recruits	19	1219	2	2
Anderson 1972 [28, 29] Canada	Adults	29	1170	1 + 3	3
Anderson 1974#3 [26] Canada	Adults	34	611	2	3
Anderson 1974#1 [26] Canada	Adults	34	581	1 + 3	3
Anderson 1974#2 [26] Canada	Adults	34	560	1	3
Ludvigsson (1977P) [30] Sweden	Schoolchildren	10	236	1	3
Carr (1981T) [42] Australia	Twin adults and adolescents together	25	164	1	3
Carr (1981 A) [42] Australia	Twin adults and adolescents apart	25	128	1	3
Miller (1977) [43] USA	Schoolchildren	12 1)	118	1	5
Constantini (2011 F) [36] Israel	Adolescent female competitive swimmers	14	51	1	3
Ritzel (1961) [14, 15] Switzerland	Schoolchildren in a skiing camp	12 1)	48	1	0.2
Constantini (2011 M) [36] Israel	Adolescent male competitive swimmers	14	47	1	3
Himmelstein (1998) [35] USA	Adults	44	26	1	3
Sabiston 1974 [44]	Marine recruits	25	20	1	0.2

1) Miller included 6–17-year-old children, but mean age was not published; 12 years is the middle of the range [43]. Ritzel’s trial included “school children in two skiing courses”, but age is not described; we assume age around 12 years [14]