Cooking food increases the available nutrients by a thousand percent in some cases. It has been argued by Richard Wrangham that without cooking we simply couldn't have evolved the brains we have and, in fact, eating raw burns more calories than it consumes without an extensive food system propagated by carnivores. In a chicken/egg dilemma, the argument is that we became human because we cooked. You may be interested to know that the "sushi" you know is a post-war invention, propagated by refrigeration distributed by the US Army in occupation. Its precursor, nigirizushi, erupted all over Edo in a couple decades about 1800-1820 and was a less-fermented version of a truly funky concoction that only the Japanese had been eating (and that sparingly) since the 6th Century. Basically, you're eating mozarella fresca; 200 years ago it was parmesan and prior to that it was camembert.