Bioavailability of calcium from calcium carbonate, DL-calcium lactate, L-calcium lactate and powdered oyster shell calcium in vitamin D-deficient or -replete rats

Formulation and optimization of gastroretentive bilayer tablets of calcium carbonate using D-optimal mixture design

Gastroretentive bilayer tablets of calcium carbonate (CC) were developed using D-optimal mixture design. The effect of formulation factors such as levels of HPMC K100 M (X1), sodium bicarbonate (X2), and HPMC E15 LV (X3) on responses like floating lag time (R1) and release of CC at 1 h (R2) and 6 h (R3) was elucidated. The optimized formulations developed by numerical optimization technique were found to have short floating lag time (2.85 ± 0.98 min), minimum burst release (27.02 ± 1.18%), and controlled yet near complete release (88.98 ± 2.75%) at 6 h. In vivo radiographic studies in rabbits indicated that optimized batch displayed a mean gastric retention time (GRT) of 5.5 ± 1 h which was significantly prolonged (P < 0.05) compared to the conventional tablets that displayed a GRT of less than 1 h. The studies proved that the gastroretentive tablets can be a promising platform to improve bioavailability of nutrients having absorption window in upper gastrointestinal tract.

Research progress on applications of calcium derived from marine organisms

Calcium is an important mineral that plays an integral role in human health, especially bone health. Marine biological calcium is an abundant resource that is generally accepted and has a complex active structure. This review evaluates research progress on marine biological calcium with regards to its sources, use of calcium supplements, calcium bioavailability, and novel applications of marine calcium. The potential for future development and the use of products incorporating marine biological calcium in biomedical research and the pharmaceutical, health care, and food industries are also reviewed. The goal of this review is to provide a comprehensive documentation on resource utilization and product development from marine organisms.

Fermented pork sausage fortified with commercial or hen eggshell calcium lactate

The effects of adding commercial-grade and eggshell calcium lactate on the microbiological and physicochemical properties of Nhams (Thai-style fermented pork sausage) were studied. The Nham calcium levels were 150, 300 and 450 mg/100 g. Compared to controls (no added calcium), calcium fortification did not affect the number of lactic acid bacteria or the colour value. The shear force of Nhams fortified with eggshell calcium lactate decreased (P<0.05) from 32.2 N in the controls to 19.5-22.8 N in Nhams fortified with eggshell calcium lactate. However, Nhams fortified with commercial calcium lactate had the same shear force as the controls. Sensory scores of sour taste, flavour and overall acceptance were not different between the control and calcium-fortified Nhams at a calcium level of 150 mg/100 g.

The bioavailability of dietary calcium

This update focuses on the bioavailability of dietary calcium for humans. Fundamentals of calcium metabolism, intestinal absorption, urinary excretion and balance are recalled. Dietary factors, especially lactose and other milk components, influencing calcium bioavailability at intestinal and renal levels are reviewed. A critical examination of all the methods used for evaluating calcium bioavailability is made. This includes in vitro assays, classical and isotopic balances, urinary excretion, isotope labeling in the urine, plasma and bones, long term evaluation of bone mineralization and the use of biological bone markers. Importance and advantages of animal models are discussed. The state of the art in the comparative bioavailability of calcium in foods is detailed including a comparison of sources of calcium (dairy products and calcium salts) in human studies and in some animal studies, casein phosphopeptides, proteins, lactose and lactase and their relation with calcium bioavailability (in humans and rats). An update on the consumption of dairy products and bone mass is presented. Emphasis on peculiarities and advantages of calcium in milk and dairy products is given.

Nutritional aspects of calcium absorption

The amount of calcium absorbed in the intestine depends on habitual calcium intake. When intake is low, active transcellular calcium transport in the duodenum is upregulated and a larger proportion of calcium is absorbed by the active process than by the passive paracellular process that prevails in the jejunum and ileum. Bioavailability of the calcium source-digestibility and solubilization-plays a role under conditions of low calcium intake but is relatively unimportant when calcium intakes are high (e.g. >800 mg/d in people). Vitamin D intake is a second factor, as active calcium transport is directly and proportionally dependent on the presence in the intestinal cell of calbindin D9k, the biosynthesis of which is totally vitamin D dependent. Passive absorption in jejunum and ileum is the major absorptive process when calcium intake is adequate or high. Passive calcium absorption is a complicated function of solubility in the distal small intestine, the length of sojourn of the chyme in a given intestinal segment, and the rate of paracellular diffusion from lumen to lymph and blood. Calcium that reaches the large intestine undergoes absorption there by both active and passive processes. Probably no more than 10% of total calcium absorption takes place in the large intestine, whether calcium intake is low or high. Calcium absorption by the large bowel can assume nutritional importance under conditions of significant small bowel resection.