49, with a mean intake of 840 ± 292 mg (21 ± 7.3 mmol)/day (Ohlson et al., 1952). In each age group, calcium intake and balance were positively correlated (r = 0.43 and r = 0.44). Only six women in the younger group and eight in the older group consumed more than 1,000 mg (25 mmol)/day. In the second study (Heaney et al., 1978) of 130 premenopausal women, aged 35 to 50 with a mean calcium intake of 661 ± 328 mg (16.5 ± 8.2 mmol)/day, calcium intake and balance were positively correlated (r = 0.26). This study included very few women with intakes over 1,000 mg (25 mmol)/day. From these data, it is apparent that the plateau intake is not below 1,000 mg (25 mmol)/day. However, the intake associated with a desirable retention so that no net loss will occur cannot be identified without additional balance studies in women with calcium intakes greater than 1,000 mg (25 mmol)/day. Available balance data from a large study in men (Spencer et al., 1984), with the wide age range of 34 to 71 years will be considered under the age group of 51 through 70 years.
Bone Mineral Density. The two available intervention trials in women in this age range (Baran et al., 1990; Elders et al., 1994) support a plateau intake at or above 1,000 mg (25 mmol)/day. In 37 premenopausal women aged 30 to 42 years randomly assigned to either their usual calcium intakes of 810 ± 367 mg (20.5 ± 9.2 mmol)/day or increased dairy product consumption to a total intake of 1,572 ± 920 mg (39.3 ± 24 mmol)/day, the group consuming extra dairy products had significantly reduced vertebral BMD loss over 3 years (Baran et al., 1990). Similarly, calcium supplementation of 1,000 and 2,000 mg (25 and 50 mmol)/day in premenopausal women aged 46 and older with a usual mean calcium intake of 1,100 mg (27.5 mmol)/day significantly reduced vertebral bone loss (Elders et al., 1994). In this study, the higher total intake (3,100 mg [77.5 mmol]/day) was no more effective than the 2,100 mg (52.5 mmol)/day intake.
Factorial Approach. If the needs for calcium accretion that are described for the young adults aged 19 through 30 years are removed from Table 4-4, the AIs based on a factorial approach would be 1,360 mg (34 mmol)/day and 1,270 mg (31.7 mmol)/day for females and males, respectively. Endogenous fecal calcium losses for 191 women aged 35 to 59 years averaged 102 ± 25 mg (2.6 ± 0.6 mmol)/day (Heaney and Recker, 1994), which if substituted in Table 4-4 would not appreciably reduce the net total calcium need. As indicated earlier, these values must be considered in light of the