Aegirinweg · Outline · Element 53
Five passes through a trace element whose distribution has more to do with geology and water cycles than with eating habits. The text stays descriptive; the only thing quoted is the one wording authorized for it in the European Union.
Anyone who wants to understand the numbers in nutrition tables cannot ignore geology. Unlike calcium or phosphorus, what matters here is not just the food group but the map.
In the open ocean, levels fall within a narrow range around sixty micrograms per liter, mostly dissolved as iodide and iodate. This makes the sea the largest continuous reservoir of this element on the Earth's surface. At the boundary between water and air, volatile compounds pass into the atmosphere and return to land with precipitation — a process that loses effect the farther you get from the coast.
The Atacama Desert contains sediment crusts that formed over millions of years under extreme dryness. They were developed in the 19th century for their sodium nitrate; the iodate they contain was at first just a by-product. Today the economic relationship is reversed, and the region is one of the two major suppliers to the world market.
The second major stream comes from deep waters of the Kantō Plain and neighboring sedimentary basins. When natural gas is extracted, a brine comes to the surface whose content is many times higher than that of ordinary seawater. Separation then takes place using blowing-out or ion-exchange methods.
Hardly any other nutrient has such a well-documented administrative history. It begins in a Parisian workshop and leads through cantonal decisions to today's German food law.
Courtois extracted potassium compounds from seaweed ash for saltpeter production. When he added sulfuric acid to the residue, a violet vapor escaped and turned directly into crystals on cool surfaces. Shortly afterward, Humphry Davy and Joseph Louis Gay-Lussac classified the substance as an element in its own right; the name comes from the Greek word for violet-colored.
In 1922, the canton of Appenzell Ausserrhoden became the first European administrative unit to supply fortified table salt. Michigan followed in 1924 and documented the process scientifically over several years. In the literature, both programs are considered the starting point of a practice that now exists in more than a hundred countries under different legal frameworks.
In Germany, the addition is permitted rather than required. The relevant rules — historically the Table Salt Iodization Ordinance, today embedded in the European framework on additives and fortification — set permitted maximum levels and labeling requirements. Whether a business uses iodized salt remains a business decision, which can be read from the ingredient list.
Intake figures are not produced at the dinner table but in the lab. The methods used help determine how reliable a statement is — and where its limits lie.
The classic method uses a catalytic property: in a mixture of cerium(IV) and arsenic(III) compounds, the color develops faster the more iodide is present. So it is not the substance itself that is measured, but the speed at which it drives another reaction. More modern labs also use inductively coupled plasma mass spectrometry.
Internationally, the concentration in urine has become the standard indicator for population groups, because by far the largest share of the amount taken in leaves the body this way. What is evaluated is the median of a sufficiently large sample, not the mean — the distribution is strongly right-skewed. Reference ranges for such medians are published by international bodies and used in national surveys.
A spot urine sample reflects the state of just a few hours. Fluid intake, time between meals and time of day shift the result considerably, which is why a single result says little about an individual. Only combining many samples across a defined group produces a figure you can work with. Incidentally, choosing and interpreting lab tests is the responsibility of a physician; this section merely explains terms.
Between a scientific observation and a sentence on a package lies an authorization procedure. Its result is a list that may only be quoted word for word.
Annex XIII of Regulation (EU) No 1169/2011 lists nutrient reference values that serve solely for uniform percentage calculations on packaging. For this element, 150 micrograms per day is listed there. The number is a calculation anchor for labeling and does not describe any personal requirement; national and European scientific societies publish differing estimated and guideline values, graded by age and life stage.
Regulation (EC) No 1924/2006 ties the use of an authorized claim to a quantity condition: the product must contain a significant amount of the nutrient, usually at least fifteen percent of the reference value per hundred grams or per serving. Here that works out to about 22.5 micrograms. Anyone below this threshold may not use the wording.
For the context covered here, the EU list contains a single line. It stays unchanged, because any rewording — even a more elegant one — would fall outside the authorization:
Per Regulation (EU) No 432/2012
Iodine contributes to normal energy-yielding metabolism. In line with Regulation (EU) No 432/2012.
Energy metabolism here means all the biochemical conversions through which the body uses energy sources from food. The sentence applies to the general population, describes a normal state and makes no statement about diseases, their course or how to avoid them. Everything else on this page is editorial text and expressly not an authorized claim.
The following overview groups common food categories by the range given for them in published compilations. It is not a substitute for analyzing a specific product, but shows orders of magnitude and how widely they vary.
| Food group | Range | Note on variation |
|---|---|---|
| Table salt, iodized | 1,500–2,500 | Results from the permitted addition range, not from the raw material |
| Lean sea fish (cod, haddock) | 100–300 | Fishing area and degree of processing shift the value considerably |
| Mussels and crustaceans | 90–140 | Farming conditions have a noticeable effect |
| Seaweed, dried | very wide range | Depends on species and batch; table values are hardly comparable |
| Cow's milk and dairy products | 10–30 | Depends on feed and farming practices |
| Chicken egg | 8–15 | As above, with seasonal differences |
| Bread and baked goods made with iodized salt | 5–15 | Only if the bakery uses iodized salt |
| Vegetables from inland regions | 1–5 | Soil content has a direct effect |
Rounded values from published compilations. A single product can fall well outside the stated range; these are composition data, not a health statement.
Five points that came up repeatedly while editing this outline and that can be clarified briefly.
They are two compound forms of the same element. Iodate is the oxidized form and is considered more stable in storage, which is why it is preferred in many fortification programs. Iodide is also used. Both are listed in the ingredient list as a potassium or sodium salt.
Not in Germany. The law allows it and sets maximum levels and labeling requirements, but leaves its use up to the business. Other countries have made fortification mandatory — the legal situation varies considerably from country to country.
Because by far the largest share of the amount taken in is excreted this way, so the concentration there is closely linked to intake. A blood value reflects other variables and is not used in the same way for group surveys.
No. This regulation lists only authorized wordings and the conditions for their use. Tolerable upper intake levels are derived separately by scientific bodies and published in their own opinions.
Only if the specific product meets the quantity condition, i.e. contains at least fifteen percent of the reference value per hundred milliliters or per serving. Most commercial waters fall below this and therefore may not carry the claim.
The typeset edition expands on every chapter of this outline, adds years and sources to the chronology of fortification programs, comments on the content table line by line and gives the exact reference for every regulation quoted. Delivered as a file once payment is received.
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