Shijimi (Japanese Freshwater Clam)

Shijimi has exceptionally high ornithine content (~10-15 mg per 100g — among the highest of commonly consumed foods) plus very high vitamin B12 (44.8 μg per 100g), iron (8.3 mg per 100g), and taurine. Ornithine is involved in the urea cycle, which processes ammonia during alcohol metabolism — the biochemical basis for the 'shijimi for hangover' association. Modern Japanese functional food and supplement industries have built on this traditional folk knowledge: shijimi-extract supplements positioned for liver function, hangover recovery, and fatigue management form one of Japan's largest single-ingredient functional categories. Some products carry FFC notifications backing specific liver-function or fatigue-related claims.

Lake Shinji (Shimane Prefecture) shijimi — labeled 'Yamato Shijimi' (大和しじみ) — commands the highest established premium and is the most recognized origin in Japanese consumer markets. Lake Shinji accounts for approximately 40% of Japanese shijimi supply and has GI-recognized status. Lake Ogawara (Aomori, second largest source) also commands premium positioning, with notable supply during seasons when Lake Shinji production is limited. Tone River (Ibaraki) shijimi is the third significant source, more widely distributed in eastern Japan retail. For OEM positioning: Lake Shinji 'Yamato Shijimi' for premium gift and high-end supplement categories; Lake Ogawara for premium positioning with secondary recognition; Tone River for general retail and cost-conscious supplement formulations.