Calcium Supplementation test1
Calcium is an essential mineral with a wide range of biological roles. Apart from being a major constituent of bones and teeth, calcium (Ca) is vital for muscle contraction, nerve conduction, the beating of the heart, blood coagulation, glandular secretion, energy metabolism and maintenance of immune function.
The amount of Ca absorbed within the gut varies depending on several factors including the requirements of the body, age and sex, but is normally only about 30-40% of the dietary intake. Sufficient Ca is generally obtained from the diet via milk products, leafy green vegetables, whole grain cereals and flour, and hard water, but in some cases additional Ca may be required in a supplemental form.
Calcium Salts
There are various Ca salts available each varying in Ca content (see Appendix) and bioavailability. Many studies have shown that among the Ca salts the citrates have a greater bioavailability compared to the other forms of Ca salts such as Ca carbonates. These salts also vary greatly in solubility and absorption rates. Calcium acetate is generally the most soluble followed by Ca lactate and then in decreasing order Ca gluconate, Ca citrate and finally Ca carbonate. In contrast to the solubility of these Ca salts, Ca carbonate has the greatest absorption rate (39%) followed by Ca acetate and Ca lactate (32%), Ca citrate (30%) and Ca gluconate with the lowest absorption of 27% (Groff & Gropper, 2000).
Ca salts are used mainly for the treatment of calcium deficient states and (most commonly known) for helping the prevention of osteoporosis. Administration may be by mouth or, in severe cases, by the intravenous or intramuscular routes. Excessive amounts of calcium salts may cause hypercalcaemia. Oral administration may cause gastro-intestinal irritation and constipation and parenteral administration may cause local reactions at the injection site and soft tissue calcification (Reynolds, 1996).
It is very interesting however that certain Ca salts are not always regarded as suitable supplements for the treatment of Ca deficiencies. Although Ca has featured in medicine down the centuries, only carbonates and lactates have been regarded as medicinal forms of Ca (Emsley, 2001).
Furthermore, Ca carbonate is normally used as an over-the-counter antacid for indigestion, whereas Ca lactate is the only form that is commonly prescribed to treat Ca deficiency. As for the remaining salts, Ca chloride in small doses acts as a diuretic and Ca sulphate is used to make plaster casts (Emsley, 2001).
Although Ca salts are generally well tolerated, Ca carbonates have been shown to cause gastrointestinal side effects such as constipation, bloating, gas and flatulence. Ca carbonate is generally used as an antacid, as a phosphate binder in patients with renal failure, as an adjunct in the treatment of osteoporosis, and as a Ca supplement. When ingested Ca carbonate is converted to Ca chloride by gastric acid. Some of the Ca (39%) is absorbed from the intestines but about 85% of this is reconverted to insoluble Ca salts, such as the carbonate, and is excreted in the faeces (Reynolds, J. (Ed.), 1996). This will therefore result in only approximately 5% of the calcium in calcium carbonate being retained within the body. The prolonged use of Ca carbonate (greater than 12g daily - about 5g of elemental Ca) may lead to the milk-alkali syndrome, hypercalcaemia, nephrocalcinosis and renal insufficiency
(Hendler & Rorvik, 2001).
Supplemental Ca taken without food may increase the risk of kidney stones in women and possibly also in men. It is thought that taking supplemental Ca without food limits the opportunity for the beneficial effect that Ca may have in binding oxalate in the intestine (Hendler & Rorvik, 2001). Ca is absorbed from the small intestine by both active and passive mechanisms. To enable these mechanisms, the elemental Ca needs to be released from the Ca complexes during digestion into a soluble form (see above for the ease of solubility). Certain Ca salts are initially released from the Ca complex but then re-inserted back into an insoluble compound.
Ca salts have been reported to be incompatible with a wide range of drugs due to their interaction resulting in a precipitate (Reynolds (Ed.), 1996).
Therefore, Ca salts are inappropriate for a large percentage of the population who regularly take drugs such as tetracycline antibiotics. High intakes of Ca salts may also interfere with the absorption of other nutrients such as iron and zinc; hence they are not suitable for individuals that are deficient in iron or zinc. It has also been shown that raised Ca intakes can lead to phosphorous deficiencies, unless sufficient phosphorous is taken along side the Ca preparation (Heaney & Nordin, 2002).
Studies have shown that certain preparations of Ca (e.g., bone meal, dolomite, Ca carbonate) may contain contaminants such as lead, aluminum, arsenic, mercury, and cadmium (Clark, M., 1995). It is also believed that citrates increase the absorption of aluminum within the gut. Whitehead et al. (1997) showed that an increased dietary citrate content in rats enhanced the permeation of aluminum within the small bowel and colon.
Several forms of commonly marketed Ca salts are not actually recognized as nutritional supplements within respected texts.
In The Merck Index (2001) for example, only one of the calcium salts in the table below (Calcium Phosphate) is recognized as a nutritional supplement. Its uses are listed as: chiefly in animal feeds; mineral supplement in cereals and other foods; manufacture of glass; in dental products and fertilizers. However, the most commonly used salts such as carbonates and citrates are only apparently used for improving the baking properties of flour; the manufacture of paint, rubber, plastics, paper, polishes, insecticides and shoe dressings; cosmetics, pharmaceuticals, antibiotics and for removing acidity of wines! No mention of the worldwide use as a nutritional supplement.
Food based calcium (foodstate)
As can be seen above there are many inadequacies and potential problems by taking calcium as a salt of any kind. The calcium provided to us through food delivers calcium bound to protein complex carriers. This is how our digestive systems through evolution have developed to receive calcium and so logically this is how we should provide it. For many people supplemental calcium is helpful and, as such, a food form of calcium as a supplement is best equipped with all the necessary carriers to best match up with the biological systems in the body. As well as this simply being the most logical way to provide supplemental calcium it has also been shown scientifically to be superior to other forms: Re-natured® (food form) Calcium brought about an 8.2% decrease in diastolic blood pressure after 7 weeks' supplementation, whereas calcium gluconate brought about no significant change. Additionally, all subjects in the calcium gluconate group complained of gastrointestinal distress, which did not happen in the Re-natured® Calcium group (Vinson, J. 1987).
Different Forms of calcium Supplement:
Concentrated Sources
Bonemeal is not actually a form of Calcium but does contain a total of 40% Calcium (as well as Phosphate). It is sometimes contaminated with Strontium and/or Lead. Bonemeal is prepared from degreased Animal bones. The form of Calcium present in Bonemeal is Hydroxapatite.
Dolomite is a mixture of 21.7% Calcium Carbonate and (13%) Magnesium Carbonate.
Oyster Shell Calcium is the Calcium component of Oyster Shells. It is not a true form of Calcium however Oyster Shells contain 37% elemental Calcium (in the form of Calcium Carbonate):
Some Oyster Shell Calcium supplements have been found to be contaminated with Lead.
Chelated Forms of Calcium
Calcium Acetate consists of 25% elemental Calcium bound to Acetic Acid.
Calcium Aspartate consists of 12.5% Calcium bound to 87.5% Aspartic Acid. Between 50% and 90% of the Calcium in Calcium Aspartate is absorbed by the body.
Calcium Bisglycinate (also known as Calcium bis-Glycinate) consists of Calcium bound to Glycine. It presently regarded as the most bioavailable and most soluble form of supplemental Calcium. It is 1.8 times (180%) better absorbed than Calcium Citrate and is 21% better absorbed than Calcium Citrate Malate. It is 205 times more soluble than Calcium Citrate.
Calcium Chelate (chelated Calcium) is a general term for all forms of Calcium that consist of Calcium chelated to another organic compound. Most forms of chelated Calcium are well absorbed.
Calcium Citrate consists of 21% to 22% Calcium bound to Citrate (Citric Acid):
- Calcium Citrate dissolves easily in Water and is regarded as being well-absorbed.
- Calcium Citrate was once regarded by many orthomolecular-oriented physicians as a candidate for being the best form of supplemental Calcium. Recent evidence indicates that it may be the third best form of supplemental Calcium in terms of bioavailability - surpassed only by Calcium Citrate Malate and Calcium Bisglycinate. It is significantly better absorbed compared to Calcium Carbonate. research
People with insufficient production of Hydrochloric Acid (a condition known as Hypochlorhydria) will absorb approximately 45% of the Calcium content of Calcium Citrate supplements.
Calcium Citrate Malate is a recently developed chelate of Calcium, Citric Acid and Malic Acid. It is reported to be six times more soluble than Calcium Citrate and ten times more soluble (i.e. bioavailable in people with low Hydrochloric Acid production (Hypochlorhydria) than Calcium Carbonate).
Calcium Fumarate consists of Calcium bound to Fumaric Acid (Fumarate).
Calcium Glubionate (also known as Calcium D-Gluconate Lactobionate Monohydrate) contains 6.6% Calcium.
Calcium Gluconate consists of 8 - 9% Calcium combined with Gluconic Acid:
- This form of Calcium is poorly absorbed although (unlike other forms of Calcium) the Gluconic Acid component of Calcium Gluconate increases the bioavailability of dietary or supplemental Magnesium.
Calcium Lactate consists of 12.5% Calcium bound to Lactic Acid (Lactate):
- Calcium Lactate is reasonably well-absorbed.
- Calcium Lactate is not derived from Milk.
Calcium Malate consists of Calcium bound with Malic Acid (Malate).
Calcium Succinate consists of 22.8% Calcium bound to Succinic Acid (Succinate).
Inorganic Forms of Calcium
Calcium Carbonate is the form of Calcium found in Dolomite. It is difficult to absorb when consumed orally, in the absence of optimal levels of Stomach Acids such as Hydrochloric Acid:
- People with insufficient production of Hydrochloric Acid (a condition known as Hypochorhydria) will absorb approximately 4% of the Calcium content of Calcium Carbonate.
Calcium Chloride (CaCl2)consists of 27.2% Calcium bound to 72.8% Chlorine (Chloride).
Calcium Fluoride consists of Calcium bound to Fluorine (Fluoride).
Calcium Sulfate consists of Calcium bound to Sulfur (Sulfate).
Other Organic Forms of Calcium
Calcium Bicarbonate (Ca(HCO3)2) consists of 40% Calcium and 60% Carbonic Acid.
- The absorption rate of Calcium Bicarbonate is poor.
Calcium Carbonate (also known as Chalk, Creta or CaCO3) consists of 40% Calcium and 60% Carbonic Acid. It is derived from Coral, Limestone or Marble and is the form of Calcium present in Dolomite, Egg Shell, and Oyster Shell:
- Calcium Carbonate can cause Nausea, Flatulence and/or Constipation in some people.
- Calcium Carbonate requires more Hydrochloric Acid for its absorption than other forms of Calcium and can also deplete the body's Hydrochloric Acid supplies. Its bioavailability is significantly less than that of Calcium Citrate, Calcium Citrate Malate and Calcium Bisglycinate.
- Calcium Carbonate is a component of some Pharmaceutical Antacids.
- Calcium Carbonate is the most prevalent form of Calcium supplements.
Calcium Orotate consists of 20.6% Calcium bound to Orotic Acid (Orotate). It is reasonably well-absorbed.
Calcium Pectate consists of Calcium bound to Pectins. It is a dietary source of Calcium present in Cabbage, Carrots and Onions and is sometimes used to lower serum Cholesterol levels.
Calcium Phosphate (Ca(CPO4)2) (also known as Tricalcium Phosphate) consists of 38.7% Calcium bound to Phosphorus. It is one of the forms of Calcium that are present in the Bones. Crystallized Calcium Phosphate is a major component of the Teeth.
Di-Calcium Phosphate consists of 29.5% Calcium bound to Phosphorus.
Secondary Sources of Calcium
Calcium Ascorbate consists of 10.3% Calcium bound to 89.7% Ascorbic Acid (Vitamin C). It is used primarily as a supplemental source of Vitamin C.
Calcium Borate is a supplemental form of Boron.
Calcium Gluceptate (also known as Calcium Glucoheptonate) is a supplemental form of Calcium that contains 8.2% Calcium.
Calcium Pangamate consists of Calcium bound to Pangamic Acid (Pangamate). It is the main form of Pangamic Acid supplementation.
Calcium Pantothenate is a supplemental form of Pantothenic Acid (Vitamin B5).
Other Forms of Calcium
Calcium Glycerophosphate consists of 19.1% Calcium (and also contains Phosphorus in its structure). It is a common active ingredient of Toothpastes.
Calcium Hypophosphite is a form of Calcium that has been used clinically for the treatment of Rickets.
Calcium Levulinate is a hydrated Calcium salt of Levulinic Acid sometimes used as a supplemental form of Calcium. It contains 13.1% Calcium.
Calcium Stearate consists of 6.6% Calcium bound to Stearic Acid. It is sometimes used as a supplemental form of Calcium.
Toxic Forms of Calcium
Calcium Oxalate (CaC2O4) consists of Calcium bound to Oxalic Acid (Oxalate). It is a major component of Kidney Stones.
Endogenous Calcium
Free Calcium (also known as Ionic Calcium) is Calcium that exists within the body and which possesses an electrostatic charge. It is present in atherosclerotic plaque during the progression of Atherosclerosis.
Hydroxyapatite is a supplemental form of the form of Calcium that is naturally present in the Bones and Teeth. It is also the form of Calcium that is present in Bonemeal:
Although many companies promote Hydroxyapatite as a well-absorbed form of Calcium and despite its high expense, some studies have demonstrated that its absorption rate (bioavailability) is actually 32% less than that of Calcium Carbonate (itself a poorly-absorbed form of Calcium).
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