Dietary calcium and bone health in the elderly: uncertainties about recommendations

An adequate intake of calcium, and of other essential nutrients, has long b een established to be necessary for the development and maintenance of bone tissue. A major question remains: how much calcium is needed across the li fe cycle in relation to other nutrients, to lifestyle factors, and to hered itary determinants. The 1997 publication on the calcium, the Dietary Recomm ended Intakes (DRIs) by the Institute of Medicine (IOM), includes recommend ations for calcium intakes for males and females across the life cycle. The new guidelines for calcium consumption by the elderly are considerably hig her than given in the tenth edition (1989) of the Recommended Dietary Guide lines (RDAs), i.e., 1200 mg per day compared to 800 mg per day. The rationa le for the recommendations of increased dietary calcium are based on publis hed reports in the literature. Current understandings of bone remodeling su ggest that usual high calcium intakes could slow the rate of bone resorptio n through suppression of parathyroid hormone (PTH). Such a reduction in bon e turnover could result in a modest but transient increase in BMD for a yea r or more. Presumably this high calcium intake would also diminish the form ation of new bone tissue, as bone turnover is slowed. The major question re garding reduced turnover rates in elderly women (and men) following calcium supplementation is whether recently formed microfractures will be adequate ly replaced when PTH concentrations are so significantly reduced by the hig h calcium consumption. A brief review of the use of the multi-factorial app roach to establishing rational nutrient intake guidelines for calcium, incl uding the important role of physical activity in maintaining bone in the el derly, is offered. The Asian paradox of low-calcium intakes and low hip fra cture rates is also considered. A goal of this review is to try to find a r easonable compromise on setting the calcium recommendation for elderly subj ects in the US and Canada, and, perhaps, in much of the world. Whether meet ing that goal requires the use of a daily supplement of calcium to achieve nutrient adequacy has not been established yet, but recent dietary intake s urveys suggest that elderly American subjects, especially women, can not in gest even 800 mg of calcium per day without a supplement. (C) 2001 Elsevier Science Inc. All rights reserved.