Although, by definition, vitamins required by man cannot be synthesized within the tissues, it is important to note that bacteria within the gut can synthesis many of the vitamins required by man. The human intestinal bacteria can synthesize vitamin K, a member of the naphtoquinone family.
Vitamin K2 also called menaquinone also is a product of metabolism of most bacteria including the normal intestinal bacteria of most higher animal species. The vitamin K bacterial reactions occur, in part, in the ileum, where the menaquinone is absorbed.
Among bacteria involve in synthesizing vitamin K are: Bacteroides spp., Eg. Lenta, Propionibacterium spp., Veillonella spp., staphylococci, enterococci enterobacteria.
Most of the vitamin B12 (cyanocobalamin) required by humans comes indirectly from the meat and milk of ruminants. The synthesis of B12 is ruminant is exclusively bacterial origin. It appears most of the bacterially formed B12 I human occurs in the large bowel. It was demonstrated that E. coli, Bifidobacterium spp., Veillonella spp., Fusobacterium spp., Eurobacterium spp., and Clostridium spp., among the bacteria that synthesized B12 in the small intestine.
Folic acid and thiamine B complex vitamins are also synthesized by bacteria in the intestinal tract. Other vitamins synthesized by intestinal bacteria are:
*Biotin
*Folic acid (B2)
*Pantothenic acid (B5)
*Niacin (B3)
*(Pyridoxine) B6
Vitamins synthesis by intestinal bacteria
