Born in 1943 to a sake brewer in Fukushima Prefecture, Japan. Raised from the cradle surrounded by the fermentative microorganisms that are used to make sake and miso. Currently professor emeritus at the Tokyo University of Agriculture, a visiting professor at Hiroshima University Graduate School, Kagoshima University, Beppu University and the University of the Ryukyus. He holds various positions including visiting researcher at the Policy Research Institute, Ministry of Agriculture, Forestry and Fisheries, president of the Council for the Promotion of Improvement of the Food Self-Sufficiency Rate, president of the Society for the Protection of Whale-Eating Culture and president of the National Council for the Local Production for Local Consumption. As a professor of agriculture, Koizumi specializes in zymology, fermentology and food culture theory.
He spends much of his time writing serials for The Nihon Keizai Shimbun and various magazines, appearing on TV and in radio shows and giving lectures all over Japan. He was written over 100 single author books, including Shoku no Daraku to Nihonjin (Deterioration of Food and the Japanese), Nippon Kaishoku Kiko (Japan Great Food Travelogue), both from Shogakukan Paperback, Mazui! (Tastes Terrible!), Bukkake Meshi no Kaikan (Get a Kick out of Bukkake Rice), both from Shincho Paperback, Hakko Shokuhin Raisan (Glory to Fermented Food), from Bunshun Paperback, and Shoku to Nihonjin no Chie (Food and Wisdom of the Japanese), from Iwanami Contemporary Paperback. Despite his busy schedule, Koizumi continuously goes on food adventures, running around the world in search of delicacies.