Thiamine is metabolized in the alimentary system to form phosphoric ethers, thiamine disulfide, thiochrome, and other unidentified products. The contents of the small intestine shows the same metabolites, among which thiamine sulfate in detectable in a greater amount. Labeled pantothenate administered parenterally is progressively metabolized largely to 4-phosphopantothenate, CoA and an unidentified metabolite which are detectable in the liver, in the mucous membrane and contents of the small intestine. Labeled nicotinate is metabolized to nicotinamide within the first 15 to 30 min of research, being metabolized to a less measure to the nucleotide forms of metabolites. The contents of the small intestine manifests the same metabolites, among which nicotinamide is predominant. It has been demonstrated that the basis of the retention of vitamins in the body is formed by their transport-metabolic transformations associated with metabolite reception in the biomembranes of the alimentary tract during recycling of different duration.