Studies have shown that supplement buyers generally trust the supplements they buy. That might not be the safest assumption, as dietary supplements that are presumed helpful or neutral may sometimes cause serious side effects, as quantified by this study.
How can I safely consume seaweed?
It is relatively easy to consume most seaweeds safely, but high intakes of raw Kelp (Kombu, or any seaweed starting with Laminaria) are a very significant concern for iodine toxicity. For daily Kombu intake, proper cooking techniques should be followed for safety.