Just be careful with any seaweed. I have a friend who is an analytical chemist, who just happened to analyse some seaweed she was eating (obtained from China). the result was a very high Arsenic content. So i would be careful where I obtained it from. Also, there is the environmental impact isue. In Tasmania for instance, vast tracts of natural kelp beds have been completely decimated because of the kelp trade. Kelp is a food source and habitat for many critters, not just humans.
Unfortuately, this is just part of the down side of the natural health industry...not to mention overpopulation issues.
There are always cause and effect issues for many things.