1. Field of the Invention
The present invention relates to a calcium preparation and a method of production thereof.
2. Description of the Related Art
A shortage of calcium intake of the Japanese is attributed to the fact that since the soils in Japan are mainly constituted of acidic soils, the amount of calcium in the soils is low as compared to that in Western countries and the amount of calcium taken from agricultural crops, water or the like is small. Further, it is attributed to the fact that the intake of dairy products of the Japanese is low as compared to that in Western countries.
In “the Japanese Dietary Reference Intake (2010)” presented by the Ministry of Health, Labour and Welfare as measures against lifestyle-related diseases, calcium is included in nutrients that the Japanese are encouraged to voluntarily increase taking. In the National Health and Nutrition Examination Survey (2008), the Japanese average ingestion of calcium is 511 mg. Thus, the result is below the recommended amount per adult per day, about 600 mg to about 700 mg. Calcium plays an important role to maintain the living body itself and its functions. Further, it is not only involved in the formation of bones and teeth but also is an indispensable element for physiological functions in many organs in the living body including blood, nerves, muscles; tissues, and cells as well as maintenance of homeostasis thereof.
On the other hand, supplements and nutrition fortified food are actively used to improve preventive medicine and improve the quality of life. However, calcium is a substance whose absorption from food is low. Additionally, the bitterness peculiar to calcium prevents a continuous oral ingestion of the calcium solution as a nutrient supplement.
Under such circumstances, there has been much development in the field of calcium, and many applications and reports exist.
Jpn. Pat, Appln. KOKAI Publication No. 56-97248 (Patent Literature 1) discloses a water-soluble calcium malate-calcium citrate complex wherein characteristics in that the rate of dissolution of poorly water-soluble calcium citrate is increased in the presence of calcium malate are used. Jpn. POT National Publication No. 5-507692 (Patent Literature 2) and Jpn. PCT National Publication No. 2002-525091 (Patent Literature 3) disclose a calcium citrate malate whose water solubility is improved. However, the solution disclosed in these literatures is a calcium solution which is poor in long-term stability.
Jpn. Pat, Appln. KOKAI Publication No. 7-89852 (Patent Literature 4) discloses a technique of obtaining water-soluble calcium powder by dissolving calcium oxide fired at high temperatures in an organic acid or an organic acid-containing liquid and drying it. The water-soluble calcium powder disclosed in the literature is acidic when dissolved in water.
Jpn. Pat. Appln. KOKAI Publication No. 2003-235466 (Patent Literature 5) discloses a water-soluble mixed feed composition prepared by mixing phosphoric acid calcium salt with organic acid. The obtained solution is acidic and a composition for feed use is disclosed.
Jpn. Pat. Appln. KOKAI Publication No. 9-289877 (Patent Literature 6) discloses a technique of surface-treating hydroxyapatite particles having a size of 800 nm or less with citric acid or a citrate containing liquid or protein or peptide as a calcium strengthening agent capable of being stably dispersed and suspended for a long time without being precipitated when adding water. Jpn. Pat, Appln. KOKAI Publication No. 6-329557 (Patent Literature 7) discloses a technique of surface-treating hydroxyapatite particles with albumin and/or polyvalent organic acid to stabilize a dispersion liquid. Although the hydroxyapatite dispersion liquid disclosed in these techniques is a stably dispersed liquid, the technique is mainly preformed under acid conditions. Further, the liquid is opaque and thus aggregation is easily caused.
Adv. Mater. 1998. 10. No. 1 49-53 (Non-Patent Literature 1) discloses a technique of obtaining nano-sized hydroxyapatite crystals by irradiating a mixture of citric acid, sodium phosphate, and calcium chloride or a mixed liquid of phosphoric acid/EDTA/calcium with microwaves or heating it at 100° C. J. Coll. in Sci. 318 (2008), 210-216 (Non-Patent Literature 2) discloses that citric acid and pH have an influence on the crystal size of hydroxyapatite. U.S. Pat. No. 6,248,376 (Patent Literature 8) discloses a method of obtaining a calcium-rich composition containing a phosphate ion source, a citrate ion source, and a calcium ion source, metal hydroxide, and water by heating a mixture of calcium hydroxide, phosphoric acid, citric acid, and potassium hydroxide in the water to 100° C. All of these techniques are methods for obtaining hydroxyapatite crystals.
Jpn. PCT National Publication No. 2004-534709 (Patent Literature 9) discloses a stable and water-soluble colloidal dispersion liquid of hydroxyapatite which contains amino acid as a stabilizer. Jpn. PCT National Publication No. 2005-500231 (Patent Literature 10) discloses a stable and water-soluble colloidal dispersion liquid of hydroxyapatite which contains a bifunctional stabilizer. J. Mater. Chem., 2004, 14, 2277-2281 (Non-Patent Literature 3) discloses a water-soluble colloid of hydroxyapatite which contains amino acid as a stabilizer. In any of the literatures, a dipolar ionic stabilizer is needed to produce the water-soluble colloid dispersion liquid of hydroxyapatite.
Jpn. Pat. Appln. KOKAI Publication No. 9-175994 (Patent Literature 11) discloses a technique of obtaining a large dissolution amount of a calcium liquid by dissolving the calcium source in citric acid and/or malic acid and lactic acid.
In order to provide a composition whose readily absorbable properties are improved, Jpn. Pat. Appln. KOKAI Publication No. 9-12811 (Patent Literature 12) discloses a technique of dissolving calcium salt in lactic acid and phosphoric acid.
There are many reports described above; however, a technique of obtaining a transparent calcium preparation which is less bitter and stable at high concentration has not been established. There is still a demand for the development of more excellent techniques.