Excess iodine is readily excreted in a dose-dependent fashion. There are portions of the Japanese population that have massive intakes of iodine with apparently no ill-effects, though I wouldn't really recommend replicating that. Eating a bit of kelp here and there and overshooting slightly with the iodine is perfectly safe. Just make sure you eat enough selenium as well.

One possible problem though is in rapidly ramping up the intake, since your thyroid has become accustomed to your intake and there may be an initial hyperthyroid pulse as a result of a huge dose out of nowhere. This is more pronounced in a severely deficient person with a goiter etc. If you slowly increase dosage, taking it every day should be fine.

I have a packet of kelp flakes which come with a prominently displayed warning not to consume in excess of 1 tsp per week. Perhaps the company which produces them is simply being cautious, although the tricky thing about seaweeds is that their mineral and iodine content fluctuates significanly depending on environment and varietal. My advice would be to contact the company directly for nutritional information and then work it out from there.

I always like to point out other foods with iodine: a couple of eggs (28mcg per egg), a glass of milk/cheese/yogurt (glass of milk is about 70 mcg), some cranberry juice (very high), some fish (100mcg or so per 100 grams), or coconut flesh/cream/milk (very high).

There is a little bit of iodine in everything (usually about 10-30mcg per 100 grams), but those ones I mentioned are all high.

Contrary to popular beleif, iodine is not a rare nutrient, nor is it only high in seafood.

Iodised salt is also pretty excessive one teaspoon has two days rda in it.

So are most seaweeds. Nori would probably be the exception though, if your only having it in gram type amounts (say 1-5 - it has 16mcg iodine per gram of weight which is still very high), it shouldnt be excessive.

If you want to eat seaweed, and you do normally eat the above list of foods, you could always sub one of those out for a couple of grams of seaweed (although, personally id rather have the eggs, dairy, coconut etc!)

Hyperthyroidism and hypothyroidism can be induced by large changes in iodine consumption. The thyroid is a delicate organ. And yes, most people do seem to tolerate larger amounts to some degree, but you dont want to be the person who is suddenly sick because of rapid dietary changes.

If you moderate the seaweed, you should be okay. Although, I have no idea how much seaweed one normally eats in a sitting.

men 100-150 mg iodine per day; women 150-300 mg per iodine per day. look at the back of the packaging. if the iodine per 1 tablespoon is 330% for the serving then you know you need at least 1/3 of that serving. iodine levels fluctuate per species so some will give more than others. im using 1/4-1/2 teaspoon dolce seaweed(dried, uncooked) per week. and this is damn near safe.

You should be more worried about pollutants and heavy metals, especially if you're buying cheap nori that comes from China. A lot of Chinese nori is grown in ocean farms near industrial centers that produce prodigious amounts of heavy metals and other dangerous aquatic pollutants. Mothers and young children should be especially cautious about consuming cheap nori.

I recommend buying higher-quality seaweed from reputable companies. My favorite is SeaSnax, which is produced in South Korea and (as far as I can tell) follows strict guidelines for purity and safety:

http://store.seasnax.com/

Would one sheet (5 sheets in total weigh 11g in the packet, made in China) be safe, perhaps every few days?