Antioxidants may not reduce pregnancy complications in diabetics

Supplementation with vitamin C and E fails to reduce the risk of pre-eclampsia in women with type-1 diabetes, according to a new Irish study.

In the randomized controlled trial, 762 pregnant women with type-1 diabetes were allocated to receive either a placebo or a daily antioxidant supplement containing 1,000 mg of vitamin C and 400 IU of vitamin E from between 8 and 22 weeks' gestation until delivery (1). The results showed that both groups had similar rates of pre-eclampsia. However, women in the supplement group who had low antioxidant status at the start of the study benefited from a significantly lower risk of pre-eclampsia. The findings also support the tolerability and safety of vitamin C and E supplements, with no harm to mothers or babies reported.

According to the researchers, women with type-1 diabetes are at high risk of pre-eclampsia and preterm delivery, linked to the increased levels of oxidative stress in these individuals, which theoretically could be compensated by antioxidants. The benefit of vitamin supplementation might be limited to women with vitamin depletion.

Experts commented that these conclusions might not be valid. The cause of pre-eclampsia might be multi-factorial. Some cases might be caused by immunological factors, others by dietary factors, and others because of pre-existing medical conditions, or by a combination of these factors. Therefore any single intervention is unlikely to be effective in preventing pre-eclampsia.

1. McCance D.R. et al. Vitamins C and E for prevention of pre-eclampsia in women with type-1 diabetes (DAPIT): a randomised placebo-controlled trial. The Lancet. 2010.