Table 3

Change in serum ascorbic acid, serum α-tocopherol, and urinary excretion of 8-OHdG

MeasureWithin-group change (mean ± SE)Main effecta (± SE)Interaction effectb (± SE)
PlaceboVitamin CVitamin ECombinedVitamin CVitamin EVitamin C × Vitamin E
Ascorbic acid−0.1 ± 2.120.3 ± 3.82.6 ± 2.722.3 ± 5.420.1 ± 3.72.3 ± 3.7−0.8 ± 7.4
(μmol/l)(P = 0.96)(P = 0.0001)(P = 0.34)(P = 0.0002)(P = 0.0001)(P = 0.53)(P = 0.92)
α-Tocopherol−0.3 ± 0.50.1 ± 0.715.0 ± 2.217.5 ± 1.71.5 ± 1.416.3 ± 1.42.0 ± 2.9
(μmol/l)(P = 0.48)(P = 0.83)(P = 0.0001)(P = 0.0001)(P = 0.30)(P = 0.0001)(P = 0.49)
8-OHdG−0.6 ± 1.30.6 ± 1.10.5 ± 1.01.6 ± 1.41.1 ± 1.21.1 ± 1.20.2 ± 2.4
(ng/mg creatinine)(0.61)(P = 0.59)(P = 0.61)(P = 0.27)(P = 0.34)(P = 0.39)(P = 0.93)
  • a Main effect of vitamin C was calculated as the difference in measures between active vitamin C and placebo vitamin C groups, averaged over the two groups that were not assigned to take active vitamin E, and vice versa for the main effect of vitamin E.

  • b Interaction effect of vitamin C and vitamin E was estimated as the difference in the effect of vitamin C on the measures between active vitamin E and placebo vitamin E groups. Both main effects and interaction effect were estimated from a full model with two indicator variables and an interaction term (a cross-product of the two indicator variables).