used for desirable calcium retention is delineated under each age-specific group. In general, for growing children and young adults, data on whole body bone mineral accretion using DXA technology were used to derive a value for calcium retention to support the reported bone accretion (assuming bone is 32.3 percent calcium). The major limitation of the data available is that bone mineral accretion during growth has not been studied over a wide range of calcium intakes.
Hypertension. Many studies have investigated a possible role of calcium in lowering the risk of hypertension. In a review of 22 randomized intervention trials, calcium supplementation was found to reduce systolic blood pressure modestly—by 1.68 mm Hg in hypertensive adults—and had no significant effect in normotensive adults (Allender et al., 1996). Diastolic blood pressure was not altered in either group. More recently, a diet with increased low-fat dairy products, fruits, and vegetables, and with reduced saturated and total fat, lowered blood pressure when fed to normotensive and hypertensive adults (Appel et al., 1997). In this study, the increase in dairy product consumption provided a mean dietary calcium increase from 443 to 1,265 mg (11.1 to 31.6 mmol)/day.
Little is known about the relationship of calcium intake and blood pressure in children. A recent randomized trial on 101 boys and girls with mean age 11 years (9.9 to 13.2 years) of African American, Caucasian, Asian, and Hispanic origin showed that calcium supplementation of 600 mg (15 mmol)/day could reduce blood pressure, although the effect was much larger in children who had lower baseline calcium intakes (150 to 347 mg [3.7 to 8.7 mmol]/1,000 kcal) (Gillman et al., 1995). No further reduction in blood pressure was observed in children already consuming over 1,000 mg (25 mmol)/day of calcium by supplementing them with 600 mg (15 mmol)/day.
The influence of dietary calcium on pregnancy-induced hypertension has been investigated extensively. A meta-analysis of 14 randomized controlled trials of calcium supplementation during pregnancy found that supplements of 1,500 to 2,000 mg (37.5 to 50 mmol)/day of calcium may result in a significant lowering of both diastolic and systolic blood pressure (Bucher et al., 1996). However, the randomized controlled trial of Calcium for Preeclampsia Prevention (CPEP) in 4,589 pregnant women found no effect of