Fractional Absorption of Active Absorbable Algal Calcium (AAACa) and Calcium Carbonate Measured by a Dual Stable-Isotope Method

Abstract

With the use of stable isotopes, this study aimed to compare the bioavailability of active absorbable algal calcium (AAACa), obtained from oyster shell powder heated to a high temperature, with an additional heated seaweed component (Heated Algal Ingredient, HAI), with that of calcium carbonate. In 10 postmenopausal women volunteers aged 59 to 77 years (mean ± S.D., 67 ± 5.3), the fractional calcium absorption of AAACa and CaCO3 was measured by a dual stable isotope method. 44Ca-enriched CaCO3 and AAACa were administered in all subjects one month apart. After a fixed-menu breakfast and pre-test urine collection (Urine 0), 42Ca-enriched CaCl2 was intravenously injected, followed by oral administration of 44Ca-enriched CaCO3 without carrier 15 minutes later, and complete urine collection for the next 24 hours (Urine 24). The fractional calcium absorption was calculated as the ratio of Augmentation of 44Ca from Urine 0 to Urine 24/ augmentation of 42Ca from Urine 0 to Urine 24. Differences and changes of 44Ca and 42Ca were corrected by comparing each with 43Ca. Fractional absorption of AAACa (mean ± S.D., 23.1 ± 6.4), was distinctly and significantly higher than that of CaCO3 (14.7 ± 6.4; p = 0.0060 by paired t-test). The mean fractional absorption was approximately 1.57-times higher for AAACa than for CaCO3. The serum 25(OH) vitamin D level was low (mean ± S.D., 14.2 ± 4.95 ng/ml), as is common in this age group in Japan. Among the parameters of the bone and mineral metabolism measured, none displayed a significant correlation with the fractional absorption of CaCO3 and AAACa. Higher fractional absorption of AAACa compared with CaCO3 supports previous reports on the more beneficial effect of AAACa than CaCO3 for osteoporosis.

Stimulation of intestinal calcium absorption by orally administrated vitamin D3 compounds: a prospective open-label randomized trial in osteoporosis

“…We conducted a randomized, open-label, controlled single-center clinical trial to assess the effects of vitamin D3 compounds on osteoporosis. The primary objective was quantitative assessment of intestinal fractional calcium absorption (FCA) using a double isotope method [ 12 – 14 ]. We compared changes in FCA among patients randomly allocated to receive ELD (0.75 μg/day), ALF (1 μg/day), plain vitamin D3 (800 IU/day), or no vitamin D3 analogue (control).…”

“…However, no data regarding the effect of ELD and ALF on intestinal calcium absorption in humans are available. Therefore, in the present study, we investigated the effect of serum concentration of calcitriol on intestinal calcium absorption in post-menopausal osteoporosis patients using a double isotope method [ 12 – 14 ]. In addition, we investigated the effects of oral doses of vitamin D3 compounds on intestinal calcium absorption and its effects on other internal organs, such as bone, parathyroid glands, and kidney.…”

Research progress on applications of calcium derived from marine organisms

“…Calcium extracted from marine algae was also found to show a beneficial anabolic effect on bone skeletal calcification in animal models of osteoporosis 38 . Algal calcium prepared from oyster shell powder and seaweed has a higher bioavailability than calcium carbonate 39 .…”

Effect of anions or foods on absolute bioavailability of calcium from calcium salts in mice by pharmacokinetics

“…Calcium absorption has been measured in previous studies using mass balance techniques from an oral calcium source intrinsically labeled with a suitable calcium isotope ( Table 1 ). 6 – 10 The studies showed that calcium absorbability is as low as 20%–40% after calcium salt administration, 6 – 11 and many modern diets do not provide the recommended levels of calcium (400–1,200 mg/day). 4 , 8 , 12 Therefore, calcium supplements are recommended for the prevention of calcium-related diseases, and various calcium salts, including calcium carbonate and calcium lactate, have been examined as calcium supplement sources.…”