An evaluation of isotopic calcium absorption tests

Harrison, Joan E.; McNeill, K. G.; Wilson, Douglas R.; Oreopoulos, D. G.; Krondl, A; Finlay, J. M.

doi:10.1016/s0009-9120(73)80032-3

Cited by 24 publications

(4 citation statements)

References 16 publications

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“…However, it does have excellent reproducibility and a strong linear correlation with true absorption values obtained from the more elaborate double isotope and balance methods. (19,20) Lower calcium absorption in smokers may be one pathway by which smoking affects the rate of bone loss. However, the mechanism is still not clear.…”

Section: Discussionmentioning

confidence: 99%

Smoking Increases Bone Loss and Decreases Intestinal Calcium Absorption

Krall

Dawson‐Hughes

1999

Journal of Bone and Mineral Research

221

107

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Cigarette use is a risk factor for increased bone mineral density (BMD) loss but the mechanisms are not well understood. The relationship of smoking to rates of BMD change at the femoral neck, spine, and total body, and to intestinal calcium absorption were examined in 402 elderly men and women (32 smokers, 370 nonsmokers) who participated in a 3-year placebo-controlled study of calcium and vitamin D supplementation. Subjects in the supplemented group took 500 mg/day of elemental calcium and 700 IU/day of cholecalciferol. Two-hour calcium absorption fraction was determined three times, at 18, 30, and 36 months, with a single isotope method utilizing

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Section: Discussionmentioning

confidence: 99%

Smoking Increases Bone Loss and Decreases Intestinal Calcium Absorption

Krall

Dawson‐Hughes

1999

Journal of Bone and Mineral Research

221

107

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“…The importance of tracing food calcium rather than a soluble calcium salt was appreciated by Harrison et al , (9) who rccommended tracing milk. The difference in absorption of radiocalcium from milk compared with calcium chloride was particularly marked in disease states.…”

Section: Discussionmentioning

confidence: 99%

One-day test using stable isotopes to measure true fractional calcium absorption

Eastell

Riggs

Vieira

et al. 1989

Journal of Bone and Mineral Research

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True calcium absorption can only be measured by the time-consuming and expensive metabolic balance method and is not predicted well by measuring the fractional absorption (FA) of radiocalcium from a fixed calcium carrier. We describe here a 1 day method for measuring the actual fraction of calcium absorbed from the habitual diet (true fractional calcium absorption, TFCA) using stable isotopes of calcium. Oral and intravenous isotopes were administered with each of the three daily meals, and then the ratio of the two isotopes in the urine was measured by mass spectroscopy. In 12 subjects, TFCA determined from stable Ca correlated well with TFCA measured by the balance method (r = 0.71, P less than 0.01), and the mean values were not different (0.26 and 0.26). In contrast, no significant correlation was found between FA and TFCA. The weak relationship between FA and TFCA underscores the importance of tracing dietary calcium rather than a fixed calcium carrier in tests of calcium absorption. Using the new method, TFCA was inversely related to dietary calcium (r = -0.45, P less than 0.05), demonstrating that it could detect physiological changes in calcium absorption. Thus, this test has two important advantages: (1) it provides a simple way to measure TFCA and true fractional calcium absorption (the product of TFCA and dietary calcium), the physiologically relevant variables, and (2) because there is no radiation exposure, the test can be used in pregnant women and children, the isotopes can be prepared in advance, and several isotopes can be used simultaneously.

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“…However the technique can overestimate calcium absorption, because intestinal calcium excretion and renal calcium recycling contribute to peak plasma tracer levels. Additionally, intestinal transit time, (15, 16) volume of distribution (15, 17) and the balance between calcium absorption and clearance (15) can affect the time post-dosing that peak plasma tracer levels occur. Thus, some conclude that peak plasma isotope levels are not as reliable as dual isotope levels when measuring calcium absorption.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, some conclude that peak plasma isotope levels are not as reliable as dual isotope levels when measuring calcium absorption. (16, 18) The dual isotope method is the optimal technique to measure calcium absorption, as it accounts for endogenous fecal calcium excretion and renal calcium recycling. (15, 19) …”

Section: Introductionmentioning

confidence: 99%

Factors Associated with Calcium Absorption in Postmenopausal Women: A Post Hoc Analysis of Dual-Isotope Studies

Ramsubeik¹,

Keuler²,

Davis³

et al. 2014

Journal of the Academy of Nutrition and Dietetics

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Reduced calcium absorption is a risk factor for osteoporosis. This study examined factors associated with fractional calcium absorption (FCA) and net calcium absorption (NCA) in postmenopausal women in a post-hoc analysis of three completed dual isotope studies. Data were analyzed from fifty postmenopausal women undergoing 121 inpatient research visits in three studies evaluating changes in FCA related to correction of vitamin D insufficiency (n=19), use of proton pump inhibitors (n=21) and use of aromatase inhibitors to treat breast cancer (n=10). NCA was the product of FCA and total calcium intake in mg/day. Variables included subjects’ age, race, body mass index, serum calcium, creatinine, parathyroid hormone, 1,25(OH)2D, 25(OH)D and habitual intake of kilocalories, protein, fat, carbohydrate, fiber, calcium, iron, magnesium, oxalate, phosphorus, potassium and vitamin D based on outpatient diet diaries. In multivariate models, subjects’ age, dietary intake of kilocalories, carbohydrates, fat, fiber, calcium and potassium were significant predictors of FCA. In multiple variable models predicting NCA, dietary intake of kilocalories, fat, fiber, calcium, potassium and serum 1,25(OH)2D were significant. The square of the correlation between actual and predicted values (an approximation of R2) was 0.748 for FCA and 0.726 for NCA. Similar to other studies, this study found that age, 1,25(OH)2D and dietary calcium and fat were associated with calcium absorption. Dietary intake of kilocalories, carbohydrates and potassium were new factors that significantly associated with FCA and NCA. In summary, the study suggests that several dietary habits play a role in calcium absorption, beyond vitamin D and calcium.

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An evaluation of isotopic calcium absorption tests

Cited by 24 publications

References 16 publications

Smoking Increases Bone Loss and Decreases Intestinal Calcium Absorption

Smoking Increases Bone Loss and Decreases Intestinal Calcium Absorption

One-day test using stable isotopes to measure true fractional calcium absorption

Factors Associated with Calcium Absorption in Postmenopausal Women: A Post Hoc Analysis of Dual-Isotope Studies

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