Reef-building corals take minerals from the sea in order to build their skeletons and casings. The major mineral used in this process is calcium. This ionic calcium is reputed to have many benefits to both health and longevity, including curing digestive problems, relief of arthritic pain and mending human bone. The world's oldest man, Shigechiyo Izumi, interviewed by the Guiness Book of Records at age 115 years old, lived on the Japanese island of Tokunoshima. The island was built on coral reefs and the surrounding waters were found to be high in ionic calcium. As corals break down, they form coral sand, a substance that is rich in ionic calcium.