Niacin (Vitamin B3)
Japanese: ナイアシン（ビタミンB3・ニコチン酸）
A B vitamin involved in energy metabolism. Abundant in fermented foods because koji mold produces it.
Niacin, also called vitamin B3, is a water-soluble vitamin converted in the body to the coenzymes NAD and NADP, participating in hundreds of enzymatic reactions. Central to energy metabolism, its deficiency causes pellagra.
Koji mold can produce niacin, increasing its content during miso and soy sauce fermentation. Since rice is low in niacin, this microbial vitamin production is nutritionally significant.
Fermentation's ability to not only change flavor but also increase nutrition quietly supports health through everyday eating.