Calcium metabolism in postmenopausal osteoporosis: The influence of dietary calcium and net absorbed calcium

Abstract

A group of 85 females aged 48-77 years with postmenopausal crush fracture osteoporosis were investigated using a 7 day combined calcium balance and calcium tracer kinetic turnover study to assess the influence of dietary calcium and net absorbed calcium on bone metabolism. During the study, patients were on their habitual diet, as determined by a prestudy registration. Dietary calcium was measured after double serving of all the meals. All urine and feces were collected and analyzed for calcium content. Bone mineralization rate and bone resorption rate were determined by applying the continuously expanding calcium pool model to the tracer kinetic data. Urine calcium excretion and net absorbed calcium were correlated (r = 0.64, p less than 0.0001) with the following equation: urinary excreted calcium (mmol/day) = 2.4 + 0.4 X net absorbed calcium (mmol/day). Dermal calcium loss was not correlated with net absorbed calcium or urinary calcium. The net amount of absorbed calcium necessary to balance urinary and dermal losses was calculated to be 4.2 mmol calcium per day. The daily calcium intake necessary for obtaining a net absorbed calcium in excess of the urinary and dermal calcium losses and thereby ensure skeletal integrity was estimated to be 34.2 mmol calcium per day compared to an average intake of 27.9 +/- 7.6 (mean +/- SD) mmol/day. Net absorbed calcium correlated negatively to bone resorption rate (r = -0.31, p less than 0.005) and positively to bone mineralization rate (r = 0.29, p less than 0.01) and to calcium balance (r = 0.66, p less than 0.0001). Dietary calcium intake and calcium balance correlated positively (r = 0.38, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Association of physical exercise and calcium intake with bone mass measured by quantitative ultrasound

“…Another retrospective study also demonstrated a significant positive relationship between dairy product consumption in adolescence and BMD in young adult women [68]. The recommendations for daily intake of calcium range from 500 to 1500 mg/day in adult women, although studies suggest that the intake should be at least 1300 mg/day [69-72]. It is not entirely clear why we observed a relative lack of an effect of calcium intake on QUS measurements at the heel, but consistent with other epidemiological studies, we found an effect of high calcium intake [73].…”

Calcium-deficiency assessment and biomarker identification by an integrated urinary metabonomics analysis

“…In China, the Nutrition and Health Status Survey in 2002 indicated that less than 10% of Chinese citizens had an adequate dietary intake of calcium; the average intake was 391 mg/day, which is only 41% of the recommended intake [3-5]. Chronic untreated calcium deficiency can cause many severe consequences, including osteomalacia (osteopenia) [6], rickets [7-9], and osteoporosis [2,10,11], and has received worldwide attention [2,5]. However, the diagnosis of calcium deficiency, particularly in the initial stages, is easily missed because this state is asymptomatic and does not lead to obvious pathological changes.…”

Osteoporosis in Gastrointestinal, Pancreatic, and Hepatic Diseases

“…Calcium absorption occurs through both transcellular and paracellular pathways; net absorption is reduced by calcium secretion and endogenous calcium losses associated with the sloughing of cells into the lumen [2]. However, as calcium intake increases, nonsaturable but less efficient pathways come into play, and calcium absorption falls to approximately 10% of the amount ingested at calcium intakes above 500 mg/ day [3,4]. At low calcium intakes, the transcellular pathway dominates and provides a highly efficient means of absorption.…”