Zinc forms for supplement manufacturing

How the forms compare

SoleChem supplies five zinc raw materials for food supplements, with elemental zinc ranging from 14.3 % to 36.4 %. That range sets the powder weight behind every label claim. In the most common pairing, zinc picolinate vs gluconate, 100 mg of zinc needs 474 mg of picolinate but 697 mg of gluconate.

The contents apply to the basis shown: anhydrous for four forms, monohydrate for zinc sulfate. Zinc citrate is often supplied as a hydrate, which carries less zinc per gram than the anhydrous figure. Use the assay on the certificate of analysis for batch calculations, not the theoretical value.

The formula for zinc glycinate, C4H8N2O4Zn, is the bisglycinate: one zinc ion bound to two glycine ligands. Materials traded as zinc glycinate vary, so check that the specification describes this compound. The solubility of the glycinate and picolinate grades is stated on their specification sheets.

The soluble salts, sulfate and gluconate, taste astringent and metallic once dissolved. That matters in chewables, drink powders, effervescent tablets and gummies. In capsules and coated tablets it is rarely a constraint.

Choosing a form

No single form is the best form of zinc for every product. The right one fits the label claim, the format, the taste budget and the regulatory route. These points usually decide it.

• Label claim and space. Dense forms leave more room in a crowded multi-nutrient tablet or capsule. Gluconate needs about 2.5 times the powder weight of sulfate monohydrate for the same claim.
• Format. Sulfate and gluconate dissolve, so they suit effervescent tablets and drink powders. Citrate, glycinate and picolinate are mainly used in capsules and tablets. In gummies, plan taste masking whichever form you use.
• Handling. Zinc gluconate is hygroscopic, so limit its exposure to humid air during storage and dispensing. Zinc sulfate monohydrate is a free-flowing powder, which simplifies blending.
• Cost per milligram of zinc. Divide the price per kilogram by the elemental content before comparing quotes. Sulfate and citrate usually cost least per milligram of zinc; glycinate and picolinate usually cost more.
• Regulatory status. The form must appear in Annex II of Directive 2002/46/EC. Check this before development starts, as described below.

For a label claim of 10 mg zinc per serving, the powder weights are:

• 27.4 mg of zinc sulfate monohydrate
• 29.3 mg of zinc citrate
• 32.7 mg of zinc glycinate
• 47.4 mg of zinc picolinate
• 69.7 mg of zinc gluconate

These figures use the theoretical contents above and exclude overage. The elemental content calculator repeats the arithmetic for any claim, and the overage calculator adds a margin on top.

Zinc picolinate vs gluconate

Picolinate carries 21.1 % zinc against 14.3 % for gluconate. For the same claim it needs about two-thirds of the powder: 474 mg against 697 mg per 100 mg of zinc. Gluconate dissolves in water and suits dissolving formats; picolinate is mainly used in capsules. Zinc picolinate is listed in Annex II of Directive 2002/46/EC. The zinc picolinate vs gluconate comparison covers the pair in more detail.

Zinc gluconate vs citrate

Citrate carries 34.2 % zinc, more than twice the 14.3 % of gluconate. A 100 mg zinc claim needs 293 mg of citrate or 697 mg of gluconate. Citrate is slightly soluble, so it suits tablets and capsules rather than clear drinks. Gluconate dissolves fully, but its taste and hygroscopicity need managing.

EU regulatory status

Directive 2002/46/EC permits only the minerals in its Annex I, in the chemical forms listed in its Annex II. Zinc is listed in Annex I. Annex II lists zinc citrate, zinc gluconate and zinc sulphate.

Annex II also lists zinc bisglycinate. Confirm that the zinc glycinate specification matches that substance before relying on the entry. Annex II also lists zinc picolinate. The guide to permitted forms in EU food supplements explains how to read the list.

The Directive also requires Annex II substances to meet purity criteria. The specification sheet and certificate of analysis state the standard each batch is tested against, and both come with the quote.

No EU-wide maximum amount for zinc in food supplements has been adopted under Article 5 of the Directive. Member states apply their own maximum levels, and these differ. The guide to maximum levels by EU country explains how national rules work and where competent authorities publish them.

Article 8 of the Directive requires the amount of zinc per recommended daily portion to be declared on the label in numerical form. The declared figure is the element, not the salt weight. Further rules are covered in the guide to labelling a food supplement.

Foods other than supplements follow Regulation (EC) No 1925/2006, which has its own list of permitted mineral forms. Authorised claim wording is listed in the EU Register of nutrition and health claims. The health-claims guide explains how the Register works.