ABSTRACT
This chapter discusses the vitamin B<Sub>6</Sub> metabolism, function, food sources and recommended intakes and status assessment. Vitamin B<Sub>6</Sub> is the commonly used term for all 3-hydroxy-5-hydroxymethyl-2-methyl pyridine derivatives. A variety of measures are used to assess vitamin B<Sub>6</Sub> status, but there is no consensus as to which measure is best or what levels indicate adequate status. Indirect measures of vitamin B<Sub>6</Sub> status involve measurement of metabolic products of vitamin B<Sub>6</Sub>-dependent enzymatic reactions, or enzyme activity. Research examining the dietary vitamin B<Sub>6</Sub> intake of active adult individuals, excluding athletes, is limited. One reason for poor nutritional status in active individuals may be long-term marginal dietary intakes associated with either poor dietary choices or reduced energy intake. Plasma pyridoxal 5'-phosphate (PLP) concentrations typically increase within the first 5 min of exercise and stay elevated during exercise, which increases the probability that PLP will be metabolized to 4-PA and lost in the urine.
