The present invention relates to a method for producing a fermented product of natural materials comprising nucleic acids in an amount of 3 to 4g or less on the basis of 70g of protein content or 24g of dietary fiber content in the fermented product by adding microorganisms and fermenting the mixture to reduce carbohydrate content and to increase beta-glucan content in natural materials, a fermented product of natural materials produced by said method, and a food product or a medicine product which comprises said fermented product.
