Calcium Citrate
Calcium citrate is the calcium salt of citric acid ; it is widely used in the food sector as a synergistic antioxidant additive (E333), exploiting at the same time its acidity-correcting and flavor-enhancing properties (orange candies , sugared almonds , chewing gum, fruit and fruit juices ). Reading between the lines of nutritional labels , this additive is also commonly found in cheeses and many frozen baked products .
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Calcium citrate is known to be an important and widespread calcium supplement , an essential mineral for the good health of bones , teeth , but also of the entire organism. For the same purpose it can be added to so-called fortified foods , therefore artificially enriched with this and possibly other nutrients .
Each gram of calcium citrate contains approximately 210 milligrams of elemental calcium, just over half that contained in one gram of calcium carbonate. These two salts represent the most common sources of calcium in supplements and dietary products intended for the integration of the mineral, often enriched with vitamin D to facilitate its absorption . Since this becomes optimal in an acidic environment, calcium citrate is indicated for people suffering from hypochlorhydria and can also be taken on an empty stomach . Conversely, people who suffer from stomach acidity should prefer calcium carbonate, to be taken together with meals; alternatively, calcium carbonate can also be taken on an empty stomach in association with fruit juice or citrus juice , natural sources of citric acid also containing small quantities of calcium citrate.
Bioavailability
Carbonate salt has the advantage of convenience and in healthy people its absorption is practically identical, or only slightly lower, than that of calcium citrate.
Despite what has been stated, often for purely commercial purposes, various studies [ 1 , 2 , 3 ] underline the absence of significant differences in terms of absorption and bioavailability of calcium citrate and calcium carbonate in healthy people.
In some documents [ 4 , 5 ] there is talk of a better absorption of calcium citrate compared to calcium carbonate. However, considering the much higher cost of the citric acid salt, in healthy subjects the cost-effectiveness ratio is clearly in favor of calcium carbonate [ 3 ] . Based on the literature consulted, in subjects in good health, calcium carbonate taken in conjunction with meals represents the most cost-effective form of supplementation. Conversely, calcium citrate is preferable in cases of hypochlorhydria, which is in turn linked to the use of drugs against gastritis , peptic ulcers or gastroesophageal reflux , such as proton pump inhibitors and histamine H2 receptor antagonists [ 6 ] . The same goes for patients undergoing gastric by-pass surgery , in which calcium citrate is preferable to carbonate [ 7 ] .
Side Effects and Advice
Regardless of the source of calcium chosen, remember that the percentage of mineral absorbed depends primarily on the dose: it is maximum for intakes of less than 500 mg and tends to decrease for higher intakes. Therefore, in the event that the doctor recommends supplementation with 1000 mg of calcium per day, it could be useful to divide the dose into two different daily intakes of 500 mg (a choice that must obviously be discussed with the doctor himself). In fact, we would like to remind you that the use of calcium-based supplements should be discussed in advance with your doctor, especially in the presence of illnesses or the simultaneous intake of drugs or other supplements. Conditions such as kidney stones , hyperparathyroidism and concomitant therapy with antacids , digoxin or tetracycline antibiotics ( tetracycline , demeclocycline, doxycycline , minocycline or oxytetracycline), could in fact make them contraindicated or require a dose adjustment.
Side effects of calcium citrate, in addition to increased gastric acidity in susceptible individuals, may include small intestinal disorders such as bloating , nausea , and constipation .
Kidney stones
The relationship between the intake of calcium supplements and the risk of kidney stones is still uncertain, given the conflicting epidemiological evidence, with studies even attributing a protective effect to calcium supplementation. In any case, one of the benefits classically ascribed to calcium citrate is the lower tendency to form kidney stones, while for commercial purposes it is even attributed a preventive role against the pathology. This is probably referring to the well-known alkalising effect of urine exerted by citric acid; However, remember that increasing the urinary pH reduces the risk of cystine, xanthine and uric acid stones , but increases the probability of the formation of renal concretions of calcium phosphate , calcium carbonate , magnesium phosphate and struvite [8] . Therefore, in the presence of kidney stones, before taking calcium citrate supplements it is very important to consult a doctor beforehand.
