Pyridoxine Requirements
All animal species so far studied require B6' The dietary requirement of mice is increased by feeding rations high in protein. Mter depletion mice respond better to pyridoxine than to the aldehyde or the amine. This is puzzling, since only the latter two have been found in the coenzymes. Many microorganisms required a source of B6, although in some instances the presence of a specific amino acid in the culture medium may abolish this requirement. The human requirement is not firmly established. Infants apparently require in the neighbourhood of 0.3 mg per day. In adults 0.5 mg daily was found to be insufficient.
A figure of around 1.5 to 2.0 mg per day is a reasonable estimate for adults and readily obtainable from most diets, according to the Food and Nutrition Board, National Research Council, 1963 revision. It is still questionable whether man makes use of Bs compounds synthesized by intestinal microorganisms. Reports of excretion of Bs and metabolites in greater quantity than the intake are numerous.
Occurrence of Pyridoxine
The best natural sources of pyridoxine are those foods containing other members of the B complex. Yeast, rice polishings, the germ of various grains and seeds and egg yolk are outstanding sources. The vitamin is widely distributed in other foods of both plant and animal nature. In many of its sources pyridoxine is chemically bound to protein and is present in liver, for example, mainly as pyridoxal and pyridoxamine protein complexes.
