Habitual dietary calcium intakes and calcium metabolism in healthy adults Chinese: a systematic review and meta-analysis.

To investigate the metabolic differences of calcium requirements between Chinese and Westerners, we examined systematically the characteristics of calcium metabolism in Chinese adults with habitual dietary calcium intakes. We searched PubMed, Cochrane Library, SinoMed, and National Index to Chinese Newspapers & Periodicals, from inception to March 17, 2015, as well as the bibliographies of any relevant papers and journals, for trials assessing calcium metabolism in healthy Chinese adults within 18-60 years of age on the typical Chinese diet. We extracted a standardized dataset from metabolic studies that reported intake, retention, urinary excretion, faecal excretion and/or fractional absorption of calcium. We pooled data with a random effects meta-analysis. Of 2,046 citations identified by the search strategy, 12 studies (comprising 137 participants, 13 aggregate data deriving from 257 individual data) met the inclusion criteria. Metabolic data with self-chosen or typical Chinese diets were analyzed. Mean daily intakes of calcium ranged between 288 and 948 mg. Mean calcium retentions of each study were between 13 and 294 mg/d. The overall pooled value for dietary intake, urinary excretion, faecal excretion, retention and fractional absorption of calcium were 583 mg/d, 117 mg/d, 381 mg/d, 72 mg/d and 33.3%. Dietary calcium intake and faecal calcium excretion explained almost 85% of the heterogeneity of calcium retention. Chinese adults could maintain a positive calcium balance with plant-based diets at calcium intakes as low as 300 mg/d through increasing fractional calcium absorption and decreasing calcium excretion in urine and faeces.