okinawa, japan. why do people live so long there? what's the key? >> they eat mostly a plant-based diet. only about 25%, though of how long we live is dictated by diet. the other 75% is how people interact with each other, their sense of purpose and their social network. they're put into little groups of five when they're 6 years old called mawais and that adds years to life expectancy. >> another spot where people live very long is the community of seventh day adventist in loma linda, california. >> yeah. they demonstrate that americans can live a lot longer. adventists live ten years longer than the average american. my good friend just died at 106 this week. they take their diet right out of the bible, genesis chapter one. they eat mostly plants, beans and nuts. then they have this ritual on