Translation of a-t 2025; 56: 97-8
SIDE EFFECTS Caution: excessive iodine intake as a result of the consumption of algae products
According to the German Federal Institute for Risk Assessment (BfR), the maximum tolerable chronic intake of iodine for adults in Germany is 500 µg per day.1 Germany is an iodine-deficient region, but excessive intake can lead to thyroid disorders. People who had an iodine deficiency in the past and have (undetected) functional thyroid autonomies may in particular react more sensitively to iodine and develop hyperthyroidism, including acutely triggered hyperthyroidism, if they suddenly consume very high levels.1
Some algae contain very high levels of iodine. The Federal Institute for Risk Assessment therefore recommends that foods containing algae be given a warning and their iodine contents indicated from an iodine content of 2,000 µg/100 g dry matter.1
According to a national investigation carried out in 2025, however, in around two thirds of 56 algae products that were suspected of having a high iodine content due to their presentation and composition the labelling recommended by the Federal Institute for Risk Assessment was either incomplete or missing entirely.2 The actual iodine content of 19 products containing algae has now been tested, including salads, snacks, noodles, tea and vegan fish replacement products: the tests showed that the iodine contents varied significantly between 10 µg and 8,270 µg iodine per 100 g of food between the products depending on the algae type* and the manufacturing. In three of the products tested, the levels were so high that even consuming standard amounts resulted in quantities well above the recommended daily maximum. For example, one cup (150 ml) of a rooibos tea with kombu (dried brown algae) that was tested was a good ten times above the recommended maximum at 5,655 µg iodine, with no information about the iodine content or recommended intake and no warnings. Even products with a moderate iodine content such as wakame salad contribute significantly to the total intake with 315 µg iodine per standard portion (150 g) and should therefore not be consumed too frequently.3
| * | Examples of different iodine contents (in each case per 100 g dry matter): Nori 1,000-15,000 µg, kombu 200,000-590,000 µg |
German consumer organisations are calling for mandatory labelling of foods that contain algae to indicate their iodine content, recommended intake, warnings and demand statutory maximum quantities of iodine.2,3 We also think this is necessary, –Ed.
| 1 | BfR: FAQ on iodine intake and iodine deficiency, version of February 2021; https://a-turl.de/ii6g |
| 2 | Verbraucherzentrale Bundesverband [Federation of German Consumer Organisations]: algae in focus: source of nutrients with a health risk?, version of February 2025; https://a-turl.de/r8hi |
| 3 | Verbraucherzentrale.de: foods containing algae: good source of iodine or a risk?, 26 November 2025; https://a-turl.de/2mcm |
© arznei-telegramm (Berlin/Germany), December 2025, protected by copyright laws.