Share the table

The body letters have spent a month on the hidden numbers. From here they go to other people's tables, to learn how the longest-lived people on earth ate and, as much, how they shared it. We begin on an island.

In 1949, four years after the war that leveled it, American officials surveyed what the people of Okinawa were eating. The answer was mostly one thing. Sweet potato, the purple and orange kind, supplied the bulk of their calories, by the most careful later count around two-thirds. Rice was a small share. Soy came as tofu nearly every day; bitter melon, called goya, was stir-fried with egg; kombu seaweed went into the pot; a little fish, and pork mostly on festival days, the whole animal, nothing wasted. The island ate about a tenth fewer calories than mainland Japan, and far less fat, sugar and salt. Before a meal the old people said a Confucian phrase, hara hachi bu: eat until you are eight parts full. You met that phrase in the key on the Blue Zones; this is the table it came from.

In 1975 a Japanese cardiologist named Makoto Suzuki began following the island's oldest people, and his study, carried on with the brothers Bradley and Craig Willcox, became the longest record of its kind. For decades Okinawa had more hundred-year-olds per head than anywhere in Japan, and Japan more than anywhere on earth, with low rates of heart disease, stroke and the cancers that fill Western hospitals.

Here is the part the diet books skip. It ended. The American bases came in 1945 and the drive-ins after them, and the generation raised on canned pork and hamburgers did not inherit its grandparents' numbers. By 2000 Okinawan men had slipped to the middle of Japan's prefectures for life expectancy. The table was never the island. It was the generation that kept it, and they kept it together, in the one thing the surveys counted least: the moai, small circles of friends formed in childhood who met, ate and looked after each other for life. Nobody on that island ate alone.

It's a Sharing key because a people's food is the simplest door into their life, and this month the body letters walk through it. If you have a thyroid condition, the seaweed belongs in a conversation with your physician first; kombu is heavy in iodine. Vault Human coaches and doesn't treat.