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Notes...............medicine
????? Turnover of Vitamin B-6 Pools and Vitamin B-6
Requirements of Humans
by Stephen P. Coburn
Taken from The Annals of the New York Academy of
the Sciences, Conference on Vitamin B-6, Volume 585, 1990.
- Major vitamin B-6 pool is in muscle and is unavailable to other tissues
except through tissue destruction. No data on response of pool to changes
in B-6 intake in non-growing animals.
- Second largest pool is liver which processes most of ingested B-6. B-6
content in liver expected to change rapidly in response to dietary intake.
- Major excretory route for B-6 is urinary pyridoxic acid. B-6 intake is
80-90% found in urinary pyridoxic acid. Urinary excretion rapidly adjusts
to balance intake.
- B-6 highly conserved in conditions of low intake. Rapidly growing
organisms need more.
- Data on minimum B-6 requirement for long-term health is inadequate.
Current RDA appears generous. Reduction below RDA do reduce B-6 blood
concentrations, urinary excretion and saturation of various enzymes
increase response to tryptophan load and alter various other indices of
B-6 status. However, the point at which these changes become unhealthy
is unknown.
- Shifts between metabolite pools and fluid pools may contribute to
decrease in plasma pyridoxal phosphate seen in pregnancy.
- Vitamin B-6 is pyridoxine.
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