In 2008, the famous American actor Jeremy Piven decided not to enact in 'Speed the Plow', a play written by David Matten. The reason he gave, was sickness arising from mercury poisoning. The main culprit behind this poisoning was a high sushi diet. It seemed the actor indulged in sushi. As a result his mercury levels shot up dramatically and hence he suffered from mercury poisoning. As fish is the main ingredient of sushi, too much intake can increase mercury levels.
Read more at Buzzle: http://www.buzzle.com/articles/mercury-poisoning-from-sushi.html