Pre-eclampsia is a common pregnancy related condition, which contributes significantly both to maternal and perinatal morbidity and mortality. The precise pathophysiology of pre-eclampsia is uncertain, and the development of effective preventive strategies remains elusive. Schoenaker and colleagues conducted a systematic review and meta-analysis of observational studies reporting dietary intake and dietary patterns. The findings indicated that women with a low dietary calcium intake were more likely to be diagnosed with gestational hypertension, while there was a suggestion (although not statistically significant) of a beneficial effect of a diet rich in fruits and vegetables on risk of pre-eclampsia. This is in contrast to the findings of systematic reviews and meta-analyses of randomised trials in pregnancy evaluating calcium supplementation and anti-oxidant vitamin C and E supplementation. The validity of any systematic review is reliant on both the underlying methodology and the quality of each of the included studies; the review by Schoenaker and colleagues is limited by the observational nature of the included studies. Please see related article: http://www.biomedcentral.com/1741-7015/12/157/abstract.