Available evidence does not warrant adjusting calcium intakes based on dietary protein intake. Other Food Components Caffeine induces a short term increase in renal calcium excretion and may modestly decrease calcium absorption. The skeletal effects of caffeine are modest at calcium intakes of 800 mg per day and above. Special Populations Amenorrheic women produce lower levels of circulating estrogen and alter calcium homeostasis. Young women with amenorrhea resulting from anorexia nervosa have reduced net calcium absorption, high urinary calcium excretion, and a lower rate of bone formation.
Exercise induced amenorrhea also results in reduced calcium retention and lower bone mass.
Decreased estrogen production at menopause is associated with accelerated bone loss, particularly from the lumbar spine, for about five years. Lower levels of estrogen are accompanied by decreased calcium absorption efficiency. Studies indicate that increasing calcium intake will not prevent the rapid Trabecular bone loss that occurs in the first five years after menopause. Calcium responsiveness of cortical bone appears to be less dependent on menopausal status. In addition, lactose-free dairy products are available.