Scottish Seaweeds as Sustainable Sources of Micronutrients: Mineral Composition, Vitamin B₁₂ Content, and Safety...

Seaweeds (macroalgae) are increasingly recognized as potential nutrient-dense components of human diets and promising contributors to sustainable food systems. The unique nutritional profile, along with a rich content of soluble fiber and bioactives, has led to growing interest in the potential of seaweeds in addressing micronutrient insufficiencies, particularly in plant-based diets where traditional sources of certain micronutrients are limited. This study aimed to evaluate selected Scottish seaweed species by quantifying key micronutrients and estimating their potential contribution to dietary intakes while also determining heavy metal and iodine concentrations to assess consumer exposure risk. In addition, the study investigated practical mitigation strategies to reduce iodine and heavy metal levels, with the objective of delivering nutritionally valuable seaweed products that are both safe and aligned with dietary guidelines. Eleven wild seaweed species obtained from the north coast of Scotland together with two farmed seaweed species from the west coast were analyzed for mineral and heavy metal content using inductively coupled plasma-mass spectrometry (ICP-MS), and vitamin B₁₂ content by an enzyme-linked immunosorbent assay. Seaweed iodine and heavy metal content were used to assess potential health risks. Additionally, some seaweed species were subjected to a blanching process in water heated at different temperatures to assess the effects on reducing seaweed iodine and heavy metal content. All wild and farmed Scottish seaweeds contained detectable levels of vitamin B₁₂, with the highest content observed in Fucus species, with F. serratus showing a mean value of 148.0 ± 42.5 μg/kg dry weight. This was estimated to potentially provide 49% of the RNI for vitamin B₁₂ in a 5 g portion. Among the minerals analyzed, a 5 g portion of seaweed was estimated to provide notable amounts of the RNI for potassium (up to 18%), magnesium and calcium (around 10%), and iron (up to 83%), but these were dependent on seaweed species or whether farmed or not. Most seaweeds, however, contained high iodine levels that were estimated to pose a risk to health. Blanching of A. esculenta, S. latissima, and F. serratus for 5 min at 80°C showed that seaweed iodine content could be reduced by around up to 90% in all three species, while in the latter two species it additionally reduced levels of arsenic by 39% and 52%, respectively. Scottish seaweeds show strong potential as sustainable sources of essential micronutrients, particularly for populations who do not consume animal products, such as vegetarians. However, the bioavailability of vitamin B₁₂ was not assessed in this study and should be examined in future work. In addition, heavy metal concentrations must remain within safe limits to minimize potential health risks. Therefore, future studies should focus on optimizing harvesting and processing methods to ensure health risks are minimized while the nutritional benefits are optimized.