Background: Preeclampsia is still the main cause of fetal and maternal morbidity and mortality. During the past decades, numerous clinical reports and trials have described various methods to prevent or reduce the incidents of preeclampsi through diet therapy. Objective: To determine the possibility of preventing preeclampsia through calcium supplementation, vitamin C and E supplementation, carbohydrate restriction or sodium restriction. Design: Systematic review of trials from 1995-2005. Searches were made in two electronic databases; Medline and PubMed. Main outcome measures: Development of preeclampsia. Results: Calcium supplementation: 6 studies were analysed. 5 studies were randomized, double blind and controlled with placebo. 1 study was a case/control study. The main differences were the size of the studies (30-4589 women) and the populations investigated (high risk vs. low risk of development of preeclampsia, mean daily calcium intake through diet). 5 studies concluded with positive effect of calcium supplementation. The largest study (studying 4589 low risk women) observed no differences between the calcium group and the placebo group. Vitamin C and E supplementation: 4 studies were analysed. 2 studies were randomized, double blind and controlled with placebo, they both studied women at high risk of preeclampsia. One of them concluded with effect of vitamin C and E, the other observed no effect. 2 studies were case/control studies. One observed higher risk of developing preeclampsia with a low vitamin C diet, the other showed decreased plasma levels of vitamin C and E in preeclamptic women. Carbohydrate restriction: Only 1 study was analysed. This was a prospective cohort study of 3771 pregnant women. Dietary intake of sucrose in the second trimester was investigated through a quantitative food frequency questionnaire. This study suggests that high intakes of sucrose increase the risk of preeclampsia. Sodium restriction: Literature shows common agreement that sodium restriction does not prevent preeclampsia. Conclusions: Calcium supplementation does not prevent preeclampsia in healthy nulliparous women. May be beneficial in a select group of women considered at high risk for preeclampsia, or in women with a low daily calsium intake. Vitamin C and E supplementation may reduce the risk of preeclampsia, but there is too little evidence to draw final conclusions. Multicentre trials are needed to show whether vitamin supplementation affects the occurrence of preeclampsia in low-risk women, and to confirm the results in larger groups of high-risk women. Carbohydrate restriction: Low intakes of sucrose during second trimester of pregnancy has shown promising effects in the prevention of preeclampsia in one cohort study. Final conclusions can not be drawn from one study. Sodium restriction does not prevent preeclampsia.