The difference between "Doburoku" and "Sake" is whether or not it is filtered at the final stage of production. Rice, rice ko-ji, and sake yeast are combined and fermented, but if you filter like sake, all the nutrients of the by-products produced by fermentation will be removed. Since Doburoku is not filtered at all, it can be said to be a healthy liquor that can be taken with the nutrition of by-products.