Calcium supplements are a valid aid in case of reduced intake of the mineral with the diet or increased need. For this reason they are recommended especially to people who are allergic or intolerant to milk and dairy products, during pregnancy and lactation, and to women in the postmenopausal period.
Not all calcium supplements are the same. In fact, inside we do not find elemental calcium but its salts (calcium phosphate, calcium carbonate, calcium gluconate, etc.). We are indeed talking about a very reactive element, which is combined with other substances for technical and functional needs; depending on the compound with which it is associated, for example, the solubility in water, the bioavailability and the percentage of tot grams change. Even in nature, calcium is never present as an element but is found in various compounds, generically called calcium salts.
We must therefore be aware that ingesting a gram of a calcium salt, for example calcium carbonate, does not take a gram of elementary calcium, but much less (in this case 0.4 grams, or 400 mg). This very important consideration is often naively or "cunningly" ignored even by the calcium-based supplement manufacturers themselves. On the contrary, a serious product that complies with the regulations in force, shows on the label the quantity of elementary calcium, making the conversion based on the raw material used. In this regard, the wording "calcium carbonate 2500 mg" is equivalent to "calcium (carbonate) 1000 mg" whereas if we find on the label the writing "calcium carbonate 1000 mg" we are in front of a product with an elementary calcium content 2.5 times lower than the previous ones; the brackets, therefore, make the difference.
Below is a simple calculation form to find out the amount of elemental calcium contained in x grams of a given raw material (to insert decimals, use the dot rather than the comma, eg 5.5 and not 5.5).
Recommended intake levels of calcium (mg / day) LARN, 1996
|
supplements | Elementary Ca | |
Calcium carbonate | 40% | |
Calcium citrate | 21% | |
Dibasic calcium phosphate | 23% | |
Tribasic calcium phosphate | 38% | |
Calcium lactate | 13% | |
Calcium gluconate | 9% |
Calcium carbonate and calcium citrate are the most commonly used preparations in calcium supplements, since gluconates and lactates contain a lower percentage of elemental calcium and are more expensive. Some of these forms, however, find space in the pharmaceutical field; the calcium chloride is for example used intravenously as a cardiotonic and in the presence of severe hypocalcemia.
Calcium carbonate, in particular, contains the highest percentage of elemental calcium and its intake is recommended in conjunction with meals, because gastric juices increase its bioavailability by disintegrating the tablet; it can also be taken without food while sipping citrus juice, for example to prevent a meal rich in fiber (whole grains and vegetables) from limiting absorption. In addition to being the most common preparation used in calcium-based supplements, it is frequently included in the composition of antacid drugs.
Calcium citrate, on the other hand, contains less elemental calcium but is more easily absorbed on an empty stomach (it is indicated in the presence of hypochloridria or hypoacidity). With the same elementary calcium, it costs up to twice as much as the calcium carbonate on the finished product.
To increase mineral absorption, calcium is sometimes associated with vitamin D (cholecalciferol); for the same reason the daily dose is often divided into two assumptions, generally at the main meals.
Finally, it is important not to exceed the recommended doses and ask your doctor or pharmacist for advice on any contraindications or interactions with medicines taken at the same time (for example, calcium supplements can alter the absorption of tetracyclines, decreasing their effect).
