Commercially available kelp and seaweed products – valuable iodine source or risk of excess intake?

Abstract

Background: Seaweeds and kelps, also known as macroalgae, have long been common in the East-Asian diet. During recent years, macroalgae have entered the global food market, and a variety of macroalgae products are now available for consumers. Some macroalgae species are known to be particularly rich in iodine, but little data regarding the iodine content of macroalgae-containing foods exists.
 Objective: The aim of this research study was to analyse the iodine content in a large variety of commercially available macroalgae-containing foods and supplements and to evaluate whether such products are sources of adequate dietary iodine.
 Design: Ninety-six different products were collected after surveying the Norwegian market for commercially available macroalgae products, collected from three categories: 1) wholefood macroalgae products (n = 43), 2) macroalgae-containing foods (n = 39), and 3) dietary supplements containing macroalgae (n = 14). All products were analysed for iodine content by inductively coupled plasma-mass spectrometry (ICP-MS).
 Results: The iodine content in one portion of wholefood macroalgae products ranged from 128 to 62,400 μg. In macroalgae-containing foods, the iodine content ranged from 30 to 25,300 μg per portion, and in supplements it ranged from 5 to 5,600 μg per daily dose. The species with the highest analysed iodine content were oarweed, sugarkelp and kombu, with mean iodine levels of 7,800, 4,469 and 2,276 μg/g, respectively. For 54 products, the intake of one portion or dose would exceed the tolerable upper intake level (UL) for iodine.
 Discussion and conclusion: The iodine content in the included products was variable and for most products high, exceeding the tolerable upper intake level (UL) if consumed as a serving or portion size. The labelling of macroalgae species included, and declaration of iodine content, were inadequate or inaccurate for several products. As macroalgae-containing products are unreliable iodine sources, inclusion of such products in the diet may pose a risk of consuming excessive amounts of iodine.

Iodine from brown algae in human nutrition, with an emphasis on bioaccessibility, bioavailability, chemistry, and effects of processing: A systematic review

“…In most European countries, including Norway, it is not mandatory to declare the iodine content of seaweed products. The iodine content is rarely indicated on the packaging of seaweed products available in and from Norway today, and when it is provided, it often deviates from the measured values of iodine content (Aakre et al., 2021). Insufficient labelling or declarations have also been observed by others (Bouga & Combet, 2015).…”

“…Currently, the safe consumption of brown algae is therefore heavily reliant on specific measurements of algae from each location and each set of processing conditions, as well as the homogeneity of the raw material. Care should be taken to provide representative samples for iodine analysis to avoid significant variability between the iodine content provided on the food packaging and the actual iodine content, an issue relevant to many food products containing seaweeds on the market today (Aakre et al., 2021).…”

“…Thus, in these population groups, there is a risk of developing thyroid disorders as a consequence of excessive iodine intake. The iodine content in seaweed food products on the market is often high, and values up to 12,000 μg/g were found in a study assessing the iodine content of commercially available products (Aakre et al., 2021). Thus, it is not surprising that consumers of seaweed can have higher intakes than the recommended maximum intake.…”

“…Safe consumption of brown algae requires both that the iodine content is within the tolerable amounts per serving size per day and the availability of information on iodine content on the food packaging. Many seaweed products contain excessive iodine (Aakre et al., 2021; Bouga & Combet, 2015), and the majority of consumers are unaware of the importance of avoiding excessive iodine in their diet. The market availability of many seaweed products thus introduces a risk of excessive iodine consumption.…”

Atomic spectrometry update: review of advances in the analysis of clinical and biological materials, foods and beverages

“…Again the study demonstrated that different seaweed species had varying concentrations of I, ranging from 33 to 391 mg g À1 and the author also noted the importance of the differences when looking at I dietary intakes. Levels of I with respect to dietary intake were investigated in various wholefood macroalgae, and in food products and dietary supplements, containing macroalgae, 216 employing TMAH/ protease digestion followed by ICP-MS analysis. The levels of I in seaweeds varied considerably, as previously discussed, and so did the I concentration in the food products analysed, likely due to the use of different seaweed species in the ingredients.…”