Calcium forms for supplement manufacturing

How the forms compare

The four calcium forms SoleChem supplies differ most in calcium per gram. Calcium carbonate carries 40.0 % and calcium citrate 24.1 %, both on an anhydrous basis. A 100 mg calcium claim therefore needs 250 mg of carbonate or 415 mg of citrate. That gap settles most calcium carbonate vs calcium citrate decisions. The two calcium phosphates sit in between and also work as excipients.

All content figures are on an anhydrous basis. Calcium citrate is supplied as the tetrahydrate, and its water of crystallisation adds mass. The as-supplied calcium content per gram is therefore lower than 24.1 %. Base label arithmetic on the assay and basis stated on the certificate of analysis, or use the elemental content calculator.

Calcium density is the main formulation variable. At typical calcium claims the salt is often the largest single component of the unit. Its content per gram sets tablet mass and capsule count. Carbonate and tricalcium phosphate give the smallest units; citrate gives the largest.

Reactivity comes next. Calcium carbonate dissolves in acids and releases carbon dioxide. In effervescent tablets this reaction is the point of the format. In acidified powders, liquids or sealed packs it causes foaming and gas build-up. Calcium citrate does not release gas with acidulants.

The phosphates also add phosphorus, which counts towards any phosphorus declaration. Both have excipient roles. Dicalcium phosphate is a common filler in direct-compression tablets. Tricalcium phosphate is used as a flow and anti-caking agent in powders. A formula can therefore contain calcium from excipients even when another salt is the declared source.

Calcium carbonate vs calcium citrate

For a 500 mg calcium claim per serving, the arithmetic scales directly. You need 1,250 mg of calcium carbonate or about 2,075 mg of calcium citrate, anhydrous basis. Carbonate keeps the unit small and usually costs less per milligram of calcium. Citrate is slightly soluble in water and stays inert with acidulants, so it suits powders and drinks where carbonate would foam. The full side-by-side is in calcium carbonate vs calcium citrate.

Choosing a form

No single form of calcium is best for every product. The choice follows from the label claim, the format and the rest of the formula.

• Label claim per unit. Powder mass scales with the claim. At 500 mg calcium you need 1,250 mg of carbonate, 1,290 mg of tricalcium phosphate, 1,695 mg of dicalcium phosphate or about 2,075 mg of citrate.
• Tablets. Carbonate and dicalcium phosphate are both used in compressed tablets. The specification sheet states whether a grade is granulated for direct compression. Ask for the grade you need in the quote form.
• Capsules. Claims of several hundred milligrams of calcium usually need more than one capsule, whatever the form. The denser forms reduce the capsule count. See capsules.
• Powders and drinks. Citrate avoids gas formation with acidulants. Tricalcium phosphate can act as calcium source and flow aid at once. See powders.
• Effervescent tablets. Carbonate reacts with the acid component and becomes part of the effervescent couple.
• Gummies. The calcium mass per serving is high, and calcium ions can interact with pectin gelling systems. Test calcium loading early in development. See gummies.
• Taste and mouthfeel. Carbonate and the phosphates are practically insoluble. They can feel chalky or gritty in chewables and suspensions.
• Cost per milligram of calcium. Carbonate is typically the lowest. Citrate is usually more expensive per milligram, partly because it carries the least calcium per gram.
• Regulatory status. All four forms fall under entries in Annex II of Directive 2002/46/EC, as set out below.

EU regulatory status

Calcium is listed as a mineral in Annex I of Directive 2002/46/EC. Annex II lists the mineral substances permitted in food supplements. Its entries include calcium carbonate, calcium salts of citric acid and calcium salts of orthophosphoric acid. Together these cover the four forms on this page. The permitted forms guide explains how the Annex II entries work.

Calcium carbonate (E170) and the calcium phosphates (E341) are also authorised food additives under Regulation (EC) No 1333/2008. Their specifications are set in Regulation (EU) No 231/2012. When a phosphate is used as a filler or flow aid, the additive conditions of use apply. The ingredient list then follows the additive rules of Regulation (EU) No 1169/2011. The specification sheet states which purity standard each grade meets.

Directive 2002/46/EC provides for EU maximum amounts of vitamins and minerals, but none have been adopted for calcium. Member states set their own maximum amounts, and these differ. The maximum levels guide explains how national rules work.

Calcium is declared as the element, in milligrams, per daily portion. The labelling guide covers the declaration format. Authorised claim wording for calcium is in the EU Register of nutrition and health claims, and the health claims guide explains the rules for using it.