Iodine forms for supplement manufacturing

How the forms compare

Potassium iodide is the iodine form covered on this page. It contains 76.4 % iodine, so about 131 µg of the salt supplies 100 µg of iodine. No single form of iodine is best for every product, and the EU choice is narrow. Annex II of Directive 2002/46/EC permits only a few iodide and iodate salts.

Iodine is declared in micrograms, so potassium iodide is a trace component in almost every formula. The salt in a serving weighs a fraction of a milligram. The practical problem is distributing it evenly, not finding room for it in a capsule or tablet.

Potassium iodide is soluble in water, alcohol and glycerol. That makes it straightforward in liquids, syrups and effervescent tablets. In solid blends, dissolution is rarely the limiting factor at such small amounts.

The iodates in Annex II are the oxidised counterparts of the iodides. They are generally regarded as more resistant to oxidation in humid conditions. Iodides are the reduced form and need more attention to moisture, light and oxidising partners, as described below.

Working with potassium iodide as an iodine raw material

Weighing a few hundred micrograms per batch unit is impractical, so manufacturers dilute the salt before final blending. A common approach is a trituration or premix on an inert carrier such as dicalcium phosphate or calcium carbonate. Geometric dilution, followed by an assay of the finished product, confirms content uniformity.

Stability points that are well established for potassium iodide:

• In moist air and light, it can slowly oxidise and release free iodine, seen as yellowing.
• Strong oxidisers can oxidise iodide when moisture is present. So can metal ions in higher oxidation states, such as copper(II).
• Tightly closed, light-protected storage and low-moisture blends limit losses.

Where iodine losses over shelf life are expected, set an overage from your own stability data. The overage calculator handles the arithmetic.

The salt has a strong bitter, saline taste in bulk. At the microgram levels used in supplements, this is rarely noticeable in the finished product.

Label-claim arithmetic uses the 76.4 % iodine content: divide the iodine claim by 0.764.

• To declare 100 µg of iodine per serving, you need about 131 µg of potassium iodide.
• To declare 200 µg of iodine per serving, you need about 262 µg of potassium iodide.

If you use a premix, divide again by the premix concentration. The elemental content calculator runs the same calculation for other mineral salts. The specification sheet and certificate of analysis that SoleChem sends with its quote state the assay and other values for the grade supplied.

Choosing the best form of iodine for a product

• Regulatory status. Only forms listed in Annex II of Directive 2002/46/EC can supply iodine in an EU food supplement. Potassium iodide is one of them.
• Label claim and format. The amounts are too small to constrain capsule fill or tablet mass. The decision is about the premix carrier and how it blends with the rest of the formula.
• Solubility. Liquids, syrups and effervescent products need a soluble form. Potassium iodide qualifies.
• Stability. Humid processing, long shelf life or a formula containing copper(II) salts or oxidisers call for protective packaging, separate premixes or an overage.
• Cost. The cost of the iodine salt per serving is negligible. Most of the cost lies in preparing the premix and testing uniformity.

Iodine often sits in multi-mineral formulas alongside selenium, zinc and copper. Check copper compatibility early if both go into one premix. The Minerals & Mineral Salts category lists the other salts.

EU regulatory status

Annex I of Directive 2002/46/EC lists iodine among the minerals permitted in food supplements. Annex II lists potassium iodide as a permitted source. It also lists potassium iodate, sodium iodide and sodium iodate. The guide to permitted vitamin and mineral forms covers how the annexes work.

The directive requires the amount of iodine to be declared as the nutrient, not as the salt, in micrograms. The labelling guide explains the full set of mandatory particulars.

The EU has not adopted harmonised maximum levels for iodine in food supplements. Member states set their own limits, and these differ. See maximum levels by EU country and check with each competent authority.

For foods other than supplements, Annex II of Regulation (EC) No 1925/2006 governs which iodine forms may be added. Potassium iodide is listed there.

Seaweed ingredients are not Annex II mineral forms. Their use, and how their iodine is declared, is not settled by Annex II and may depend on general food law and national rules. Check their status case by case, including against the novel food guide.

Any claim about iodine must be an authorised claim under Regulation (EC) No 1924/2006. Check the wording in the EU Register of nutrition and health claims and see the health-claims guide.