Sources of Calcium

Minerals. Supplementation of macrominerals to mminants is sometimes necessary. Calcium and phosphoms are the minerals most often supplemented in mminant diets. One or both may be deficient, and the level of one affects the utilization of the other. Limestone, 36% calcium, is commonly used as a source of supplemental calcium. Dolomite, 22% calcium oyster sheUs, 35% calcium and gypsum, 29% calcium, are sources of calcium. Bone meal, 29% calcium, 14% phosphoms dicalcium phosphate, 25—28% calcium, 18—21% phosphoms and defluorinated rock phosphate, 32% calcium, 18% phosphoms, are sources of both calcium and phosphoms. Diammonium phosphate, 25% phosphoms phosphoric acid, 32% phosphoms sodium phosphate, 22% phosphoms and sodium tripolyphosphate, 31% phosphoms, are additional sources of phosphoms (5). 

Calcium. Soil minerals are a main source of calcium for plants, thus nutrient deficiency of this element in plants is rare. Calcium, in the form of pulverized limestone [1317-65-3] or dolomite [17069-72-6] frequendy is appHed to acidic soils to counteract the acidity and thus improve crop growth. Such liming incidentally ensures an adequate supply of available calcium for plant nutrition. Although pH correction is important for agriculture, and liming agents often are sold by fertilizer distributors, this function is not one of fertilizer manufacture. 

Some commonly used primary nutrient fertilizers are incidentally also rich sources of calcium. Ordinary superphosphate contains monocalcium phosphate and gypsum in amounts equivalent to all of the calcium originally present in the phosphate rock. Triple superphosphate contains soluble monocalcium phosphate equivalent to essentially all the P2 5 product. Other fertilizers rich in calcium are calcium nitrate [10124-37-5] calcium ammonium nitrate [39368-85-9] and calcium cyanamide [156-62-7]. The popular ammonium phosphate-based fertilizers are essentially devoid of calcium, but, in view of the natural calcium content of soils, this does not appear to be a problem. 

Calcium. Calcium is the fifth most abundant element in the earth s cmst. There is no foreseeable lack of this resource as it is virtually unlimited. Primary sources of calcium are lime materials and gypsum, generally classified as soil amendments (see Calcium compounds). Among the more important calcium amendments are blast furnace slag, calcitic limestone, gypsum, hydrated lime, and precipitated lime. Fertilizers that carry calcium are calcium cyanamide, calcium nitrate, phosphate rock, and superphosphates. In addition, there are several organic carriers of calcium. Calcium is widely distributed in nature as calcium carbonate, chalk, marble, gypsum, fluorspar, phosphate rock, and other rocks and minerals. 

In internal or bulk settiag, which is normally carried out at room temperature, the calcium is released uader coatroUed coaditioas from within the system. This method led to the developmeat of stmctured fmits, stmctured pet foods, and a host of cold prepared desserts. Calcium sulfate (usually as the dihydrate) and dicalcium phosphate (calcium hydrogen orthophosphate) are the sources of calcium most commonly used. 

Mineral Feed. Mineral feed supplements for domestic animals and fowl usually contain a pure form of pulverized limestone. In fact, some state laws require the supplement to be at least 35% available calcium. Other sources of calcium are bone meal and dicalcium phosphate. Use as mineral feed has been a steadily growing market for limestone. The material is ground to 90% minus 0.15 mm (100 mesh) or 80% minus 0.9074 mm (200 mesh), is low in silica, and has strict tolerances on arsenic and fluorine (see Feeds and feed additives). 

Juice Purification Chemistry. Lime in juice purification serves as a source of calcium, a source of alkalinity, and a source of calcium carbonate which serves as the clarification—filtration medium. 

Occurrence. Brines are the main commercial source of calcium chloride [10043-52 ]. Some brines of Michigan, Ohio, West Virginia, Utah, and California contain over 4% calcium (27). Michigan is the leading state ia natural calcium chloride production with California a distant second. 

A former commercially important source of calcium chloride was as a by-product of the Solvay process used to produce soda ash (28). Because of environmental concerns and high energy costs, the Solvay process has been discontinued ia the United States though it is stiU used extensively elsewhere ia the world (see Calcium compounds). 

One source of calcium ions, which cause contraction of smooth muscle in arterial walls, is inflow through ion-specific channels. So, the calcium blockers block the channels, limiting inflow of calcium and keeping muscle cells in relaxed states for a longer time. 

In Figure 8.2, for the purpose of examining the effeet of variable calcium, the Sr/Ca ratios of all the plants were set to the same fixed value (0.00790). In nature this situation is rarely likely to exist because there is intrinsic vari-abihty among different plant species (Runia 1987, 1988). The fact that bone represents a long-term (ca. 7 years) dietaiy average somewhat obviates this somce of variability. To the extent, however, that the dietaiy selection of plants varies systematically, the dietary Sr/Ca ratio will reflect this difference. Consistent dietaiy differences in the selection of plants are likely to affect bone Sr/Ca, especially since plants will usually be the dominant source of calcium. It should be noted that one of the earliest paleodietary apphcations of bone... 

It may be necessary to segregate waste streams containing elevated concentrations of arsenic and selenium, especially waste streams with concentrations in excess of lmg/L for these pollutants. Arsenic and selenium form anionic acids in solution (most other metals act as cations) and require special preliminary treatment prior to conventional metals treatment. Lime, a source of calcium ions, is effective in reducing arsenic and selenium concentrations when the initial concentration is below lmg/L. However, preliminary treatment with sodium sulfide at a low pH (i.e., 1-3) may be required for waste streams with concentrations in excess of lmg/L.22 The sulfide reacts with the anionic acids to form insoluble sulfides that are readily separated by means of filtration. 

All types of muscle require calcium for contraction. In skeletal muscle, Ca++ ions are stored within an extensive membranous network referred to as the sarcoplasmic reticulum. This network is found throughout the muscle fiber and surrounds each myofibril. Furthermore, segments of the sarcoplasmic reticulum lie adjacent to each T tubule that, with a segment of sarcoplasmic reticulum on either side of it, is referred to as a triad. As the action potential is transmitted along the T tubule, it stimulates the release of Ca++ ions from the sarcoplasmic reticulum. The only source of calcium for skeletal muscle contraction is the sarcoplasmic reticulum. 

Source of calcium Sarcoplasmic reticulum Extracellular fluid (most) sarcoplasmic reticulum (some) Extracellular fluid (most) sarcoplasmic reticulum (some)... 

Organized into sarcomeres Sliding-filament mechanism of contraction Source of calcium ... 

Milk is an excellent source of calcium, phosphorus, riboflavin (vitamin B2), thiamine (vitamin Bl) and vitamin B12, and a valuable source of folate, niacin, magnesium and zinc (Food Standards Agency, 2002). In particular, dairy products are an important source of calcium, which is vital for maintaining optimal bone health in humans (Prentice, 2004). The vitamins and minerals it provides are all bioavailable (i.e. available for absorption and use by the body) and thus milk consumption in humans increases the chances of achieving nutritional recommendations for daily vitamins and mineral intake (Bellew et al., 2000). 

Gelperin, D., Mann, D., Del Valle, J. and Wiley, J. Bradykinin (BK) increases cytosolic calcium in cultured rat myenteric neurons via BK-2 type receptors coupled to mobilization of extracellular and intracellular sources of calcium Evidence that calcium influx is prostaglandin dependent. /. Pharmacol. Exp. Ther. 271 507-514,1994. 

All individuals should have a balanced diet with adequate intake of calcium and vitamin D (Table 3-1). Table 3-2 lists dietary sources of calcium and vitamin D. If adequate dietary intake cannot be achieved, calcium supplements are necessary. 

Other selective forces may also have been at work. Flatz (1987) has suggested that calcium absorption was a factor in northern Europe. Lactose is known to facilitate calcium absorption in the intestine. The northerly climate frequently prevented skin exposure to sunlight, thereby reducing the body s production of vitamin D. With little vitamin D available, calcium was poorly absorbed and conditions such as rickets could result. The ability to digest lactose would not only allow adults to use an excellent source of calcium, but the lactose would also facilitate its absorption. 

Bone is the main source of calcium in the human body. Osteoporosis, decreased calcium salt reserves in the body, has become the most prevalent bone disease in the U.S., being especially prevalent among post-menopausal women (1). Typical signs of this debilitating condition include backache with spasms, wedge fractures of the dorsal and lumbar vertebrae, and hip fractures (2). 

Lovelace et al. (20) noted that the effect of oxalic acid on calcium retention depended on the age of the animal (Figure 4). The two experimental diets contained cod liver oil and 0.3% calcium. Milk was the main source of calcium, and to one diet was added 60 mg of potassium oxalate daily. Ten-day balances were determined throughout the study until rats were 175 days of age. At 50 days of age, rats fed oxalate retained about 25% of the calcium,... 

There are two sources of calcium carbonate, ground calcium carbonate (GCC) and precipitated calcium carbonate (PCC). 

Dibasic calcium phosphate is found in nature as the mineral monetite. It is used as a food supplement and source of calcium, both in human food and ani-... 

Richter, F., Newmark, H. L., Richter, A., Leung, D., and Lipkrn, M. (1995). Inhibition of Western-diet induced hyperproliferation and hyperplasia in mouse colon by two sources of calcium. Carcinogenesis 16, 2685-2689. 

Milk is one of the best dietary sources of calcium, not only because of the significant quantity of the mineral present but also because of (1) its calcium-to-phosphorus ratio (1.3 1), which is conducive to optimal skeletal growth, and (2) the presence of nutrients such as lactose and vitamin D in vitamin D-fortified milk, which promote calcium absorption (Ziegler and Fomon 1983 Schaafsma 1983 Renner 1983). 

The bioavailability of calcium from dairy foods is considered to be excellent (Schaafsma 1983). Evidence from animal studies suggests that the form of calcium in dairy foods may influence the bioavailability of this mineral (Wong and LaCroix 1980). For example, dairy foods that contain colloidal calcium phosphate or calcium caseinate (e.g., as in Cheddar cheese) appear to be somewhat better sources of calcium than foods that contain ionic calcium (e.g., yogurt, buttermilk). However, calcium in milk and other milk products is of greater bioavailability to humans than calcium found in other food sources. According to Renner (1983), calcium utilization from skim milk powder is 85% compared with 22-74% from vegetables. Dietary fiber in plant cell... 

The sequestering and emulsifying properties of lactobionic acid suggest a commercial potential for this product. In addition, it is a solubilizing agent for calcium salts. Solutions of calcium lactobionate containing up to 70% of the salt have been prepared and may be useful as a source of calcium (Kastens and Baldauski 1952). 

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