Requirements of calcium: are there ethnic differences?

Calcium is an essential dietary element to maintain the integrity of the skeleton. A higher peak adult bone mass has been shown to reduce the risk of osteoporotic fractures later in life. It is postulated that a lifelong higher calcium intake would reduce bone loss in advancing age. Available scientific evidence seems to indicate that within any ethnic group, calcium intake is positively associated with bone mass. Controlled calcium supplementation trials in both low and high dietary calcium intake children and adolescents showed that there is an association between calcium intake and gains in bone mass. Furthermore, studies in adolescents showed that genetic inheritance and skeletal responses to hormonal changes at puberty have great influences on bone mass increments in addition to calcium intake. Interestingly, across-cultural comparisons are not convincing enough to demonstrate that lower calcium intake would predispose to higher risk of osteoporosis. It implies that the genetic inheritance and complex environmental factors may be important modulators on bone mass achievement in addition to calcium intake within any ethnic group. There are pitfalls in the current Recommended Dietary Allowances (RDAs) for calcium which are usually based on clinical studies conducted in Caucasians with higher calcium intakes and the extent of nutritional adaptation to low calcium intake is ignored. Given the fact that there are ethnic differences in calcium absorption, dietary habits, bone metabolism, physical activity and skeletal size as well as body build, the requirements of calcium in Asians may be different from Caucasians. Ideally, each nation should establish its own RDA based on the ethnic make-up of its population. In Asian countries, the major sources of calcium are derived from vegetable types of foods, fish and shell fish with edible bones, fins and shells, etc. Recent absorption studies in humans with low-oxalate and low-phytate vegetables and pulses also showed that contrary to common presuppositions, these vegetables with low calcium chelators do have a comparable calcium absorbability to milk. Studies on bioavailability of calcium from Asian foods and diets are warranted in order to identify rich sources of calcium.