Seaweed consumption: remain vigilant to the risk of excess iodine intake

Over the last few years, seaweed has become increasingly common on our plates. Fresh, dried or as a food supplement, its iodine content varies and can sometimes be high. ANSES assessed the risk of excess iodine intake from the consumption of seaweed-based products. In view of the non-negligible risk of exceeding the upper limit of safe intake for iodine, the Agency advises against the consumption of seaweed and seaweed-based food supplements by certain at-risk populations, and recommends that regular consumers remain vigilant.

In a context where seaweed-based products are increasingly being offered to consumers, ANSES assessed the risk of excess iodine intake associated with the consumption of seaweed in foods and food supplements. Its expert appraisal focused on iodine-containing seaweed likely to be consumed in France.

It identified seaweed species particularly rich in iodine, such as the brown kelp Laminaria spp and Saccharina spp, and the red algae Gracilaria verrucosa.The Agency stresses that iodine levels in seaweed-based products can vary according to:

  • the conditions under which the seaweed is produced;
  • the method used to process the ingredient or food;
  • the type of seaweed-based preparation (powder, extract) used in food supplements.

ANSES's assessment was based on the tolerable upper intake level for iodine established by the European Food Safety Authority (EFSA) at 600 µg per day for adults and adjusted for each age group of consumers. In addition, French regulations have laid down a maximum daily dose for iodine in food supplements of 150 µg.

As the iodine content in the various seaweed-based products can be high, their consumption presents a non-negligible risk of exceeding the upper intake levels, particularly if the seaweed is consumed in combination with seaweed-based food supplements.

Regular excessive intake of iodine can cause thyroid dysfunctions as well as certain adverse effects, particularly cardiac or renal effects.

The Agency therefore advises against the consumption of food and food supplements containing seaweed by the following at-risk groups:

  • people with thyroid dysfunction, heart disease or kidney failure;
  • people taking medication containing iodine or lithium;
  • pregnant or breastfeeding women, without seeking medical advice.

Parents are reminded that they should exercise caution regarding their children's consumption of seaweed-based products, as there are insufficient data for measuring the risk involved.

People with an iodine deficiency are reminded that they should not consume products containing seaweed to correct this deficiency.

In general, the Agency recommends that consumers choose supply channels regulated by the authorities for all seaweed-based foods and food supplements.

Furthermore, ANSES stresses that mentioning the iodine content in seaweed-based products would be useful to allow consumers to monitor their daily iodine intakes.

The Agency highlights the importance of assessing the population’s actual level of iodine exposure through a study of the frequency and patterns of seaweed consumption as well as the levels of iodine in the seaweed consumed.

Lastly, ANSES reminds healthcare professionals of the need to report to its nutrivigilance scheme any adverse effects liable to be associated with the consumption of food supplements.