AU713772B2 - Calcium-containing foods - Google Patents

Description

Calcium-Containing Foods Technical Field The present invention relates to foods that contain calcium.

Background Art Calcium is an essential element to live. It plays an indispensable role to exhibit biological functions for individual lives, particularly in higher animals, to retain their whole living body.

Furthermore, calcium is the major element of the bones.

The reason why the calcium concentration in the bones is extremely high is considered to not only retain their structural strength but store excessive calcium just in case that they can release and supply calcium quickly when the body fluid calcium concentration becomes insufficient. It is well known that bone weakening diseases such as osteoporosis is caused by insufficient calcium intake, which results in dissolution of a lot of calcium from the bones into body fluid to prevent calcium insufficiency in it.

On the other hand, the calcium concentration differs between the inside and outside of cells by 10 000 times. This is because calcium needs to rush from the outside into the inside of cells through quick opening of the calcium channels on the cell surface when each cell exhibits a certain function. If the difference of the calcium concentration between the inside and outside of cells is not large enough, this quick flow of calcium into cells becomes difficult and, subsequently, various life-keeping operations (muscle contraction, hormone secretion, signal transmission in nervous system, etc.) cannot be performed smoothly.

Since calcium has such subtle regulatory functions for living phenomena, its abnormal concentration or metabolism in the body fluid can result in various diseases. For instance, when calcium intake is not enough and insufficiency in the calcium concentration in the body fluid lasts long, more calcium will be dissolved into the body fluid from the bones. Accordingly, the body fluid calcium concentration becomes slightly higher than the normal level, then the intracellular calcium concentration does so. In such a case, cells are in an extremely stimulated "excitatory situation." Chronic hypertension would occur if this happens in muscles surrounding blood vessels (vascular smooth muscle cells), and epilepsy could happen if it happens in the brain cells.

It is extremely important for maintaining a healthy living body to strictly retain the body fluid calcium concentration within the optimal range. In common higher animals, the calcium concentration in body fluid is always strictly retained within the range from 8.5 to 11.0mg/dL and, if it comes out of this range, strong adjusting mechanism will work.

Except for artificial means like injection, oral intake is the only method to take calcium into body fluid in a natural manner. In other words, the only entrance of calcium into the body is a digestive tract (in particular, duodenum and upper intestine). In contrast, the only exit for calcium in the body is a kidney. Once calcium enters into a body, it is excreted into only urine. Also, calcium in the body is stored in only the bones.

C04495 The body fluid calcium concentration is controlled by the three essential functions above; storing in and releasing from the bones, absorption from the digestive tract, and excretion into urine at the kidneys. Also, multiple hormones regulate these functions.

When the body fluid calcium concentration becomes lower than the normal level, more calcium is absorbed in the intestine, more calcium is dissolved into the body fluid from the bone, and more calcium once excreted into the urine is reabsorbed into the blood at the kidney. In contrast, when the body fluid calcium concentration becomes higher, calcium absorption is suppressed in the intestine, excessive calcium is stored in the bone, and reabsorption of the calcium into the blood, which has once excreted into the urine, is suppressed at the kidney.

The hormones such as calcitonin, parathyroid hormone (PTH), and active vitamin D control the regulatory functions at the digestive tract, bones, and kidney. Calcitonin, PTH, and vitamin D are produced in thyroid, parathyroid, and kidneys, respectively. These organs have sensors, which monitor the body fluid calcium concentration sensitively and secrete these hormones depending upon the changes in the body fluid calcium concentration.

In humans, regardless of whether or not calcium is taken from the digestive tract, about grams per day of calcium is transferred from blood into urine at the kidney and about 98% thereof is reabsorbed into the blood at the kidney again. Namely, the difference of approximately 200 to 250mg of calcium is excreted with urine to the outside of the body every day. Thus, if calcium intake is not sufficient, body fluid calcium is excreted little by little every day, and, to compensate it, calcium is dissolved from the bones into the body fluid little by little every day. Accordingly, calcium in the bones is gradually lost, and bone strength is getting lost as well.

As indicated in Figure 1, while calcium is mostly absorbed in the digestive tract of humans when the amount of dietary calcium intake is small, its absorption efficiency is gradually lowered as the dietary intake amount increases. For example, when about 1000mg of dietary calcium is taken daily, about 25% thereof (250mg) is absorbed in the normal condition. Namely, if this amount of dietary calcium is taken every day, calcium balance in an individual body is well maintained.

Among all nutritional elements, calcium is the one that the most people are likely to insufficiently take. Table 1 indicates comparison between the required amount of calcium intake per day and the average of the actually taken amount in various age and gender groups provided by the United States Food and Drug Administration (USFDA). As indicated in this table, the actual intake amount is lower than the required amount in almost the all of groups. It is well known that the actual amount of calcium intake in Japan is far below the required value. Accordingly, calcium is a nutritional element that many people do not take sufficiently even in the developed nations where shortage of food merely happens.

Table 1 Age Grou s Recommended Value Actual Value US Infant 0-6 monthw 400mg 250-330mg by milk alone 6-12 months 600mg 400-700mg Child 1-5 years 800mg Ca 800mg 6-10 years 1800-1200mg Youth 11-24 years 1200-1500mg M: ca 900mg I F:<900mg -v H k" 3 i:7 o3 C04495 Male 25-65 years 1000mg 900mg years or older 1500mg <900mg Female 25-50 years 1000mg 900mg or older Hormone Replacement 1000mg 900mg (postmenopausal) No Hormone Replacement 1500mg or older 1500mg <600mg Pregnancy and Lactation Periods 1200-1500mg 900ma Japan Uniformly 600mgr 500m As mentioned above, although calcium is an extremely important nutritional element to retain healthy living bodies, many people do not take it sufficiently. Also, very few people take calcium with good absorption efficiency.

Calcium as dietary material used for food and health food is produced from limestone, calcium phosphate ore, bones from cows and others, egg shells, shells of oysters and scallops, sea plants such as seaweed, kelps, and so forth. Calcium made from these raw materials shows different absorption rates in the digestive tract when they are taken as food. Although calcium in these raw materials mostly exists as calcium carbonate or calcium phosphate, these are sometimes converted into the organic salts such as citrate, lactate, gluconate, and malate in order to increase the absorption rate in the digestive tract. However, calcium from each of the above raw materials are disadvantageous in that the absorption rate in the digestive tract is not enough, or that, even if the absorption rate in the digestive tract is not bad, the cost is high due to its poor productivity. Thus, they are not satisfactory as food materials for calcium supplementation.

Disclosure of the Invention An objective of this invention is to provide calcium-containing foods, which have an excellent calcium absorption rate in the digestive tract.

To accomplish the above objective, the present inventors researched and developed a new calcium material, found that the calcium-containing composition obtainable by baking sea urchin shells showed an extremely higher absorption rate in the digestive tract compared to the calcium from other sources, and filed a patent application on this calcium composition (Japanese Patent Application No. 91694/94 corresponding to Unexamined Published Japanese Patent Application No. 75526/95).

The present inventors further investigated the calcium-containing composition obtainable by baking sea urchin shells, and consequently, found that the strict control of the production process provides the calcium composition particularly suitable for food use with an excellent calcium absorption rate in the digestive tract, thereby accomplishing this invention. Namely, the present inventors found that a calcium-containing composition particularly suitable to food use can be produced by baking sea urchin shells at the temperature ranging from 500 to 1500°C for 6 hours or longer. The main character of the calcium-containing foods of this invention is to provide excellent calcium balance even at very high calcium dosage, which usually lowers the calcium absorption rate in the digestive tract.

The calcium-containing composition of this invention is obtainable by removing the meat attached to the sea urchin shells, washing the shells with water, then baking them at a high temperature.

C04495 The species of sea urchin used as the raw materials is not necessarily restricted. It can be an animal belonging to the class of echinoidea in the phylum of echinodermata, such as Murasaki-uni (Anthocidaris), Aka-uni (Pseudocentrotus), Bafun-uni (Hemicentrotus), Ezobafun-uni (Strongylocentrotus), Gangaze (Diadema), Shirohige-uni, etc. To remove the meat attached to the sea urchin shells, one can use a spatula to chip off the ovary and meats attached to the inside of the sea urchin shells. The sea urchin shells, from which the meats are removed, are washed with water and subjected to baking.

The roes of sea urchins are eaten in Japan, Korea, etc., and their shells and other meats are usually discarded. The calcium-containing foods of this invention can be produced with low cost because the sea urchin shells, which have been discarded, are used for the raw materials.

Furthermore, that sea urchins have been eaten means that their toxicity need not to be concerned.

Moreover, problems such as environmental pollution or waste treatment caused by discarded sea urchin shells can be solved.

Sea urchin shells are baked at a high temperature in an oven that can reach high temperature, such as electric oven, gas oven, fuel oil oven, and so forth. The baking temperature ranges from 500 to 1500°C, preferably 700 to 1500°C, and more preferably 1000 to 15000C. The baking time is 6 hours or longer, preferably 8 to 24 hours, and more preferably 10 to 18 hours.

The calcium-containing composition obtainable by the above baking method can be converted into various calcium salts such as calcium carbonate, calcium hydroxide, calcium citrate, calcium arginate, calcium lactate, calcium malate, calcium gluconate, calcium picolinate, calcium phosphate, calcium chloride, etc. depending upon its use.

In general, such various forms of salts of the calcium-containing composition obtainable by baking sea urchin shells can be applied to food use by mixing them with other food materials. For instance, they can be mixed into cookies or drinks.

Brief Description of the Drawings Figure 1 is a conceptual chart showing the correlation between the calcium intake amount and calcium absorption rate.

Figure 2 is a graph indicating the change of the blood calcium concentration in parathyroidectomised rats.

Figure 3 is a graph showing total urinary calcium excretion in parathyroidectomised rats.

Figure 4 is a graph demonstrating total faecal calcium excretion in parathyroidectomised rats.

Figure 5 is a graph exhibiting calcium balance in parathyroidectomised rats.

Best Mode for Implementing the Invention The following Examples explain this invention, but are not to be construed to limit the scope of the invention.

T C04495 Example 1 Characterisation of Baked Sea Urchin Shell Calcium Sea urchin shells were washed with water. After meats and seaweed attached to the shells were removed, the shells were divided into four groups, then baked in an oven at 1000°C for 2, 4, 6, or 8 hours. As a result, the sea urchin shells were turned into the following colours.

Group A (2-hour baking): grey white Group B (4-hour baking): slightly clouded white Group C (6-hour baking): white Group D (8-hour baking): white After baking, the sea urchin shells in all groups were roughly broken but kept their original shape of the shells.

To prepare citrate salts for food use from each group of baked sea urchin shells, the same amount of the baked shells of each group was put into separate reaction tanks, and citric anhydride and water were slowly added to the shells with agitating. The shells in all groups gradually absorbed the citric acid solution, which was generated by the reaction of citric anhydride and water, with releasing heat to form a solid of calcium citrate. As the reaction proceeded, the baked sea urchin shells that retained their original shape collapsed into rough powder.

In the above process, the time required to convert 100kg of baked sea urchin shells of each group into citrate salts was about 2 hours for Groups C and D, about 4 hours for Group B, and 7 hours or longer for Group A. The resulting citrate salt powder was fine in Groups C and D, while rough in Group A. The colour of the resulting powder was white for Groups C and D, slightly clouded white for Group B, and grey white for Group A.

In case that the calcium thus obtained by baking sea urchin shells is contained in foods, for instance, calcium fortified cookies, the powder of Group C or D could be added to other ingredients of cookies as it was without further grinding before addition, while the powder of Group B or A was too rough and was considered to need to be ground with a mill before mixing with other materials.

Furthermore, the powder of Group A would affect the colour of the final product food due to its colour of grey white.

Thus, when the calcium-containing composition obtainable by baking sea urchin shells is used as food, baking for 6 hours or longer provides the one that is easily processible, fine, pure white, and applicable to mixing with other food materials.

The same experiment was conducted except for baking at a temperature of 500'C and 1500'C and the same result was obtained.

Example 2 Production of Baked Sea Urchin Shell Calcium Sea urchin shells were washed with water and attached meats and seaweed were removed.

The resulting shells were baked in an oven at 10000C for 12 hours. By this baking process, the calcium contained in the sea urchin shells in the form of calcium carbonate was mostly converted into 35 calcium oxide and the organic components contained in the sea urchin shells were completely L) SC04495 CO4495 eliminated. The sea urchin shells after baking were roughly broken but kept their original shape.

Furthermore, the original colour was completely lost and converted into pure white. The resulting baked product was exposed to carbonate gas with agitating slowly, converted back to calcium carbonate, then ground to very fine powder with a grinder.

Example 3 Absorption of Baked Sea Urchin Shell Calcium into the Body The rats from which their parathyroids were resected by surgery (parathyroidectomised rats) were fed with low calcium diet (the normal rat diet but containing only 0.1% calcium) for 7 days. They were fasted for the last 12 hours of the 7-day period. The blood calcium concentration of these parathyroidectomised rats was stabilised at about 4 to Smg/dL, which is approximately a half of the normal level (8.5 to 11mgdL). Twenty-four animals (including the same number of males and females) with good health conditions and sufficiently low blood calcium concentration were selected from these parathyroidectomised rats, then divided into four groups to give six animals (three males and three females) per group.

The above-described low calcium rat diet was mixed with either sea urchin shell calcium in the form of calcium carbonate obtained in Example 2, oyster shell calcium, or calcium carbonate from limestone. The same low calcium diet but containing no calcium was also prepared. These four types of diets were given to the above four groups of parathyroidectomised rats with the low blood calcium concentration. Namely, all of the parathyroidectomised rats were divided into the following four groups.

Group 1: low calcium diet group Group 2: limestone-derived calcium group Group 3: oyster shell calcium group Group 4: sea urchin shell calcium group Abundant calcium was given to Groups 2, 3, and 4. Namely, the rats were given the diet containing calcium in such an amount that daily calcium intake per rat was 380mg per kg body weight, the average body weight of all rats. This dose corresponds to 22.8 grams of the daily dose for a human adult with 60kg body weight, which largely exceeds the daily required intake indicated in Table 1. The total daily diet intake per rat in all Groups 1 to 4 was at most 12 grams. The total daily dose of calcium samples given to each group were contained in the first four grams of 12 grams of the total daily diet. All rats were confirmed every day to take all of the first four grams of the diet. Water was given ad libitum.

Blood was sampled from each rat in all groups every 24 hours from the beginning of this test (0 hour) for 7 days (168 hours from the beginning of the test) to measure the blood calcium concentration.

The whole amount of urine and faeces of each rat in all groups were collected 24 hours just prior to the beginning of feeding the above diets (-24 to 0 hours), every 24 hours for 2 days right after the beginning of feeding (0 to 24 hours and 24 to 48 hours) and the calcium in the samples were quantified if necessary. As described above, orally taken calcium is either absorbed in the intestine or C04495 not absorbed and excreted into faeces. Once absorbed in the intestine, there is no way to go out of the body but to be excreted into urine. Therefore, quantifying the calcium contents in urine and faeces informs the total calcium excretion out of the body within a predetermined period of time (in this experiment 24 hours just before and 48 hours immediately after the beginning of the feeding).

As shown in Figure 2, the blood calcium concentration of Group 3 (oyster shell calcium diet group) and Group 4 (sea urchin shell diet group) showed almost the same pattern throughout the 7day period, and significantly higher than that of Group 1 (low calcium diet group) and Group 2 (limestone calcium diet group) at almost every time point. This demonstrates that, even when calcium is given such a large amount as to lower calcium absorption, calcium from oyster shells and sea urchin shells are superior to limestone calcium in calcium absorbability into the body from the intestine and that they highly improve the condition of hypocalcaemia caused by parathyroidectomy and the low calcium diet.

On the other hand, as Figure 3 shows, comparison of urinary calcium excretion by the rats of all groups reveals that the rats of Group 3 (oyster shell calcium diet group) and Group 4 (sea urchin shell calcium diet group) excreted a significantly higher amount of calcium into the urine than those of Group 1 (low calcium diet group) and Group 2 (limestone calcium group). This indicates that the blood calcium concentration of rats of Groups 3 and 4 was elevated so that urinary calcium excretion was raised (calcium reabsorption from urine to blood was suppressed) compared to Groups 1 and 2, which supported the data in Figure 2. Although no significant difference was observed between Groups 3 and 4, urinary calcium excretion was slightly higher in Group 4 than Group 3.

Calcium contents in all faeces sample from each rat of Groups 1, 3, and 4 were measured to compare total faecal calcium excretion at every 24 hours. As shown in Figure 4, faecal calcium excretion was almost the same (namely, almost the same amount of calcium was absorbed in the intestine) in Group 3 (oyster shell calcium diet group) and Group 4 (sea urchin shell calcium diet group) 24 hours just before the beginning of feeding of the above diet (-24 to 0 hours) and immediately after the beginning of feeding (0 to 24 hours). However, Group 3 (oyster shell calcium diet group) showed significantly higher faecal calcium excretion than Group 4 (sea urchin shell calcium group). As a result of comparison of total faecal calcium excretion during 0 to 48-hour period, Group 3 (oyster shell calcium diet group) exhibited more significantly higher faecal calcium excretion than Group 4 (sea urchin shell calcium diet group) and thus the statistical significance became larger.

As demonstrated above, sea urchin shell calcium was significantly superior to oyster shell calcium in the calcium absorption rate in the intestine even at high dosage. Additionally, the difference between these two groups was small in 0 to 24-hour period then expanded in 24 to 48-hour period. This suggests that both groups absorbed calcium similarly well because the bodies required immediate supply of calcium in the first 24 hours when the animals were in the condition of extreme hypocalcaemia. In contrast, in the next 24 hours when the blood calcium concentration was elevated to near the normal range, only sea urchin shell calcium with really good absorbability retained a high absorption rate, while the absorption rate of oyster shell calcium dropped rapidly.

In addition, the calcium balance, namely the total amount of calcium taken (or lost) by the individual bodies in each time periods of -24 to 0, 0 to 24, and, 24 to 48 hours, was calculated by the C04495 equation, "Total Oral Calcium Intake" -("Urinary Calcium Excretion" "Faecal Calcium Excretion").

The calcium balance within each period in Groups 1, 3, and 4 was shown in Figure 5. As indicated by this figure, sea urchin shell calcium was significantly superior to oyster shell calcium by p<0.01 in total calcium balance of a body.

The results are summarised below.

1) Sea urchin shell calcium demonstrates superior absorbability in the intestinal tract compared to limestone-derived calcium and significantly improved hypocalcaemia caused by parathyroidectomy and low calcium diet even at high dosage.

2) Sea urchin shell calcium showed a higher calcium absorption rate and calcium balance not only in the condition of hypocalcaemia in which the body requires rapid calcium supplementation but also at the relatively normal body fluid calcium concentration even at high dosage.

As described above, calcium absorbed from diet is transferred into the body fluid such as blood, and the body fluid calcium concentration is strictly retained within a constant range from 8.5 to 11.Omg/dL. Therefore, the living body shows the reactions such as suppression of calcium absorption at the intestinal tract (Reaction promotion of calcium excretion in the kidney (Reaction and storing the excessive calcium in the bones (Reaction C) when body fluid calcium concentration becomes too high. The fact that the large total amount of actually acquired calcium by the individual bodies (superior in calcium balance) was obtained in the above Examples does not mean that calcium is stored in the blood but that more calcium is incorporated into the bone. In other words, among all of the three regulating mechanisms of body fluid calcium, Reaction C works well as well as Reactions A and B.

Industrial Applicability The present invention provides a calcium-containing composition, particularly suitable for food use, having an excellent calcium absorption rate in the digestive tract, processibility, and fine and pure white appearance. Excellent health foods can be produced by mixing this calcium-containing composition with other food materials.

V C04495

Claims (4)

1. Foods which comprise a calcium-containing composition that is obtainable by baking sea urchin shells at the temperature ranging from 500 to 1500°C for 6 hours or longer.

2. Foods which comprise a calcium-containing composition, said foods being substantially as hereinbefore described with reference to any one of the examples.

3. Use of a calcium-containing composition for preparing calcium-containing foods, wherein said calcium-containing composition is obtainable by baking sea urchin shells at the temperature ranging from 500 to 1500°C for 6 hours or longer.

4. A method for preparing calcium-containing foods, wherein said method comprises adding to foods a calcium-containing composition that is obtainable by baking sea urchin shells at the temperature ranging from 500 to 1500°C for 6 hours or longer. A method for preparing calcium-containing foods, said method being substantially as hereinbefore described with reference to any one of the examples. Dated 19 May 1999 CALIFORNIA CALCIUM CORPORATION Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON 0 o o 4 S 0 0 06* 2 C04495