Iodine Bioavailability and Accumulation of Arsenic and Cadmium in Rats Fed Sugar Kelp (Saccharina latissima)

Abstract

Suboptimal iodine status is a prominent public health issue in several European coun-tries. Brown algae have a high iodine content that, upon intake, may exceed the recommended dietary intake level, but iodine bioavailability has been reported to be lower than from potassium iodide (KI) and highly depends on algae species. Further, potential negative effects from other components in algae, such as cadmium (Cd) and arsenic (As), have also been addressed. In this study, we observed a lower bioavailability of iodine from farmed sugar kelp (Saccharina latissima) than from KI in female Wistar IGS rats. Urinary iodine excretion was 94–95% in rats fed KI and 73–81% in rats fed sugar kelp, followed by increased faecal iodine levels in rats fed sugar kelp. No effects on body weight, feed efficiency, or plasma markers for liver or kidney damage were detected. The highest dose of iodine reduced plasma free thyroxine (fT4) and total T4 levels, but no significant effects on circulating levels of thyroid-stimulating hormone (TSH) and free triiodo-thyronine (fT3) were detected. Faeces and urine measurements indicate that 60–80% of total As and 93% of Cd ingested were excreted in rats fed 0.5 and 5% kelp. Liver metabolomic profiling demonstrates that a high inclusion of sugar kelp in the diet for 13 weeks of feeding modulates metabolites with potential antioxidant activity and phytosterols.

Bioavailability of iodine from a meal consisting of sushi and a wakame seaweed salad—A randomized crossover trial

“…A “delayed” iodine excretion was observed in the mentioned Greenlandic study, which proposed that iodine excretion could last up to 36 and perhaps 48 h after seaweed ingestion (Noahsen et al, 2020 ). In addition to the reduced absorption, some of the iodine may have been excreted in feces, and consequently, less iodine would appear in the urine; this has been demonstrated in an animal trial with rats (Fjære et al, 2022 ).…”

The sugar kelp Saccharina latissima II: Recent Advances in farming and applications

“…Several animal feeding trials have studied the effect of including S. latissima (whole or extracts) in the diet of ruminants (Samarasinghe et al 2021a;Grabež et al 2022Grabež et al , 2023Qin et al 2023), monogastric animals (Gahan et al 2009;McDonnell et al 2010;Krogdahl et al 2021;Juul et al 2022;Fjaere et al 2022) and fish (Ferreira et al 2020;Granby et al 2020). In a feeding trial with Norwegian lambs, the effect of replacing 5% of the control diet with dry S. latissima in the finishing diet was studied.…”