tion of zero balance plus 63 mg (1.6 mmol)/day of sweat loss (Charles et al., 1983) since the balance studies were not corrected for sweat losses. The estimated calcium intake at which this level of retention would be achieved is 995 mg (23.9 mmol)/day (Figure E-3). Thus, based on balance studies in men, a calcium intake to achieve the desired zero calcium retention is about 1,000 mg (25 mmol)/day.

Other investigators have contributed balance data in men. In long-term studies, Malm (1958) assessed balance in 39 men who had calcium intakes of 460 and 940 mg (11.5 and 23.5 mmol)/day. Balance was positively associated with calcium intake, but too few men were studied at high-enough calcium intakes to identify a plateau balance level. Although small sample sizes limit their usefulness in this context, older balance studies in males (Ackerman and Toro, 1953; Bogdonoff et al., 1953; Outhouse et al., 1941; Schwartz et al., 1964) indicate that a plateau retention of calcium would be achieved with a calcium intake of 1,000 to 1,200 mg (25 to 30 mmol)/day, which is similar to that derived using the desirable retention model based on the data of Spencer et al. (1984).

Bone Mineral Density. Only one randomized, controlled, calcium intervention study in men has been reported (Orwoll et al., 1990). In this 3-year study of 77 men aged 30 to 87 years (mean age 58 years) with a mean usual dietary calcium intake of 1,160 (29 mmol)/day, supplementation with an additional 1,000 mg (25 mmol)/day of calcium and 10 µg (400 IU) of vitamin D did not significantly reduce spinal or forearm bone loss. This finding, that increasing calcium intake above a mean intake of about 1,200 mg (30 mmol)/day did not reduce bone loss further, suggests that intakes less than or equal to 1,200 mg (30 mmol)/day are adequate to maximize maintenance of bone mass in this age group.

Calcium Retention. Women have been more widely studied regarding calcium retention because they are particularly prone to osteoporosis. Several balance studies are reported in postmenopausal women with mean calcium intakes under 1,000 mg (25 mmol)/day. In 61 women with varying degrees of osteoporosis and with calcium intakes ranging from 200 to 1,000 mg (5 to 25 mmol)/day, a positive linear correlation between calcium intake and balance was noted, and was similar in women with or without vertebral fractures