Food and Pharma Application: Bioavailability of Calcium Citrate

Why Calcium is important to human body?

Calcium plays an extremely important role in human health, physical development and physiological activities of children and adolescents. It is also a mineral element that is easily lacking in the human body.

Calcium has the functions of strengthening the elasticity and toughness of soft tissues, reducing the excitability of nerve cells, strengthening the conduction function of the nervous system, maintaining the normal excitation of muscle nerves, regulating the permeability of cells and capillaries, promoting the activities of various enzymes in the body, maintaining acid-base balance, and participating in blood coagulation. Calcium deficiency can lead to many diseases such as rickets and osteoporosis. Too low calcium content in the diet can easily lead to thyroid disorders, thereby increasing the risk of fractures and kidney stones.

Calcium citrate, as an organic calcium acid, has higher solubility and bioavailability than inorganic calcium acid, has no irritation to the stomach and intestines, and can be directly absorbed by the human body without being neutralized by gastric acid. It is becoming the first choice for food calcium supplements. Calcium citrate can be used as a fortifier, tissue coagulant, and emulsifying salt in the food industry, as a chelating agent and buffer in the chemical industry, and as a calcium fortifier in the pharmaceutical industry.
 

Schematic diagram of the crystal structure of calcium citrate Ca3(C6H5O7)2•4H2O

Calcium citrate has the following application characteristics [1]:

1.Nutritional properties

The citric acid in the product undergoes the tricarboxylic acid cycle and eventually generates CO2 and H2O to produce ATP (adenosine triphosphate), which provides energy for the body and promotes its growth and development.

2. Safety

Calcium citrate is an excellent food additive and nutritional enhancer that can be added and used in the production of many foods.

3. Easy to absorb

Calcium citrate has no irritating effect on the stomach and intestines and can be directly absorbed by the human body without being neutralized by gastric acid, with a high absorption rate. The solubility of calcium citrate itself is better than other calcium biomaterials such as calcium phosphate and calcium sulfate. It can release calcium ions efficiently and steadily during the degradation process, making it suitable for use as a biomedical material, such as filling fracture defects and providing the required calcium ions in the early stages of fracture healing.

Application in the food industry

Calcium citrate is easily absorbed by the human body and is widely used in the food industry. It can be used as a nutritional fortifier in biscuits, pastries, soy milk and other foods, and can also be used as a tissue strengthener in canned tomatoes, potatoes, etc. Compare the metabolic efficiency of calcium in the blood from three oral calcium sources: calcium formate, calcium citrate and calcium carbonate [2].

The trial was a four-factor crossover trial design. 14 adult women were orally administered 1200 mg of placebo (sodium methylcellulose), calcium formate, calcium citrate and calcium carbonate after fasting. Compared with placebo, there was no significant change in the increase in serum calcium concentration and decrease in serum parathyroid hormone (iPTH) after oral administration of calcium carbonate (Figure 1 and Figure 2).

Oral administration of calcium citrate resulted in varying degrees of improvement, reaching significant levels at 135 minutes and 270 minutes. After oral administration of calcium formate, serum calcium concentration increased by 15% and parathyroid hormone decreased by 70% at 60 minutes. The area under the time curve of serum calcium concentration was extremely significantly higher for calcium formate (378mg·min/dL) than for calcium citrate (178mg·min/dL), and higher for calcium citrate than placebo (107mg·min/dL) and calcium carbonate. (91 mg·min/dL), but the difference was not significant.

HELLER et al. measured the bioavailability of 25 postmenopausal women taking 500 mg calcium citrate or calcium carbonate + 125 IU vitamin D, and evaluated it in three stages, during which each woman took calcium citrate with breakfast. , calcium carbonate. It was observed that compared with calcium carbonate, calcium citrate produced a 94% increase in the area under the serum calcium concentration-time curve, a >41% increase in urinary calcium, and a 56% decrease in serum parathyroid hormone levels. A meta-analysis of 15 studies on calcium absorption and bioavailability reported that calcium citrate is 22%-27% more absorbed than calcium carbonate. From this data, it follows that calcium in calcium citrate is more bioavailable than calcium carbonate. 2.5 times[3].

Changes of serum calcium concentration over time after oral administration of different calcium sources

Changes of serum iPTH over time after oral administration of different calcium sources

Application in the medical industry

Calcium citrate can be used to treat osteoporosis and can also be used as an artificial bone material. Tan Hui et al. [6] used calcium citrate to treat osteoporosis and achieved good results. Because calcium citrate does not produce CO2 in the gastrointestinal tract, it reduces adverse reactions such as indigestion, abdominal distension, and constipation. It is especially suitable for long-term use by elderly osteoporosis patients.

Peng Lei et al. [7] specifically studied the effect of calcium citrate on fresh blood. Calcium citrate has good biocompatibility. Adding it to fresh blood can provide a suitable calcium ion concentration for fracture healing. The calcium ions dissolved by calcium citrate can be stored in the blood clot, which can provide the required calcium ions for the later stage of fracture healing. Calcium citrate has good application prospects as a bone biomaterial.

Bioavailability of different calcium sources at different concentrations[8]