Japanese people have been eating several kinds of kaisou for hundreds of years. Some of the ones most popular in Japan are nori, iwanori, hijiki, kombu, and wakame. For pictures of the most common sea vegetables here and a brief description of how they are used, check out this webpage on Eat-Japan (just click the picture to open the page)
Sea vegetables are known to have anti-cancer properties in addition to their healthful ingredients. In this short video, Dr. Michael Gregor asks, "which seaweed is most protective against breast cancer?" I found it amazing how effective sea vegetables are in fighting disease and how little one needs to consume in order to obtain large benefits.
Of course, as is evident by the statistics shown in the video, eating a plant based diet which avoids meats and dairy products as much as possible is of prime importance in reducing your chances of developing cancer and for attaining and supporting optimal health.