Calcium, nitric oxide, and preeclampsia

A relationship between calcium dietary intake and incidence of preeclampsia was proposed. In the Andean Ecuadorian population, the average calcium intake, evaluated by a 24 hours dietary recall range between 52.3% of the US RDA to 77%. The calcium intake in women with preeclampsia was significantly lower in relation with normal pregnant women. Three prospective, randomized, double-blind, placebo-controlled clinical trials to investigate the effect of calcium supplementation (2 g/day of elemental calcium) in the incidence of pregnancy-induced hypertension and preeclampsia were conduced between 1984 and 1995. All the subjects included were nulliparous, younger that 25 years old, first prenatal visit before 24 weeks' gestation, residency in Quito, and normotensives. These clinical trials showed a risk reduction in pregnancy induced hypertension and preeclampsia in the calcium group. Calcium supplementation was associated with an increase in the serum ionized calcium concentrations. Moreover, women with preeclampsia showed a significant decrease in the levels of the serum ionized calcium. Ionic calcium is crucial for the synthesis of vasoactive substances in the endothelium as prostacyclin and nitric oxide. Recent results suggest that an alteration in the action of NO may be related to a high inactivation by free radical superoxide, secondary to an inflammatory process.