Yes, easily, and kelp is where it happens. Analyses of commercial dried kombu put it around two thousand micrograms of iodine per gram, with individual samples running higher still, while the adult tolerable upper intake level is 1,100 micrograms per day. A gram of kombu in a soup stock therefore clears the daily ceiling on its own. Nori, the thin sheet used for sushi, is roughly a hundred times weaker and is not the problem. Iodine excess and iodine deficiency both disturb thyroid function, and kelp supplements in particular have produced documented cases of thyroid dysfunction, so it is the concentrated kelp products rather than the occasional nori roll that warrant care.

Natural glutamate, and a lot of it. Seaweed is graded high on free glutamate. Kombu is literally the source umami was discovered in, when glutamate was isolated from it in Japan in 1908, and traditional dashi is a glutamate extraction from kelp. No MSG needs to be added for a kombu broth to hit the same receptors. If you track glutamate reactions, treat seaweed stock, seaweed seasoning and instant miso as glutamate exposures rather than as neutral vegetables.

It is graded at the top of the salicylate scale, which surprises people who move to seaweed as a clean whole food. On a strict salicylate elimination such as the RPAH protocol, that puts nori wraps, seaweed salad and kelp seasoning in the same avoid tier as most herbs and spices. Once you are in the challenge phase it becomes a dose question, but during a baseline washout it is not a free food.

It can be. Seaweed is graded moderate for nickel because it takes trace metals up directly from seawater as it grows, and the concentration in dried products rises as the water is removed. For systemic nickel allergy syndrome, where the reaction is dietary rather than from jewellery contact, regularly eaten seaweed is worth logging alongside the usual suspects such as oats, cocoa, legumes and canned food.