Nutrition Vitamin B6

1 nutrition

1.1 food sources
1.2 dietary recommendations
1.3 absorption , excretion

nutrition
food sources

vitamin b6 distributed in foods in both free , bound forms. cooking, storage, , processing losses of vitamin b6 vary , in foods may more 50%, depending on form of vitamin present in food. plant foods lose least during processing, contain pyridoxine, far more stable pyridoxal or pyridoxamine found in animal foods. example, milk can lose 30–70% of vitamin b6 content when dried. vitamin b6 found in germ , aleurone layer of grains, , milling results in reduction of vitamin in white flour. heating occurs before freezing , canning processes other methods may result in loss of vitamin b6 in foods.

foods contain large amounts of vitamin b6 include

fortified breakfast cereals
pork
turkey
beef
bananas
chickpeas
potatoes
pistachios

dietary recommendations

the u.s. institute of medicine (iom) updated estimated average requirements (ears) , recommended dietary allowances (rdas) vitamin b6 in 1998. current ears vitamin b6 women , men ages 14 , increase age 1.0 1.3 mg/day , 1.1 1.4 mg/day, respectively; rdas increase age 1.2 1.5 , 1.3 1.7 mg/day, respectively. rdas higher ears identify amounts cover people higher average requirements. rda pregnancy 1.9 mg/day. rda lactation 2.0 mg/day. infants 12 months adequate intake (ai) 0.1–0.3 mg/day. , children ages 1–13 years rda increases age 0.5 1.0 mg/day. safety, iom sets tolerable upper intake levels (uls) vitamins , minerals when evidence sufficient. in case of vitamin b6 ul set @ 100 mg/day. collectively ears, rdas, ais , uls referred dietary reference intakes (dris).

the european food safety authority (efsa) refers collective set of information dietary reference values, population reference intake (pri) instead of rda, , average requirement instead of ear. ai , ul defined same in united states. women , men ages 15 , older pri set @ 1.6 , 1.7 mg/day, respectively. ai pregnancy 1.8 mg/day, lactation 1.7 mg/day. children ages 1–14 years pris increase age 0.6 1.4 mg/day. these pris higher u.s. rdas. efsa reviewed safety question , set ul @ 25 mg/day.

for u.s. food , dietary supplement labeling purposes amount in serving expressed percent of daily value (%dv). vitamin b6 labeling purposes 100% of daily value 2.0 mg, of may 27, 2016 revised 1.7 mg bring agreement rda. table of old , new adult daily values provided @ reference daily intake. food , supplement companies have until january 1, 2020 comply change.

absorption , excretion

vitamin b6 absorbed in jejunum , ileum passive diffusion. capacity absorption being great, animals able absorb quantities greater necessary physiological demands. absorption of pyridoxal phosphate , pyridoxamine phosphate involves dephosphorylation catalyzed membrane-bound alkaline phosphatase. products , nonphosphorylated forms in digestive tract absorbed diffusion, driven trapping of vitamin 5′-phosphates through action of phosphorylation (by pyridoxal kinase) in jejunal mucosa. trapped pyridoxine , pyridoxamine oxidized pyridoxal phosphate in tissue.

the products of vitamin b6 metabolism excreted in urine, major product of 4-pyridoxic acid. estimated 40–60% of ingested vitamin b6 oxidized 4-pyridoxic acid. several studies have shown 4-pyridoxic acid undetectable in urine of vitamin b6-deficient subjects, making useful clinical marker assess vitamin b6 status of individual. other products of vitamin b6 metabolism excreted in urine when high doses of vitamin have been given include pyridoxal, pyridoxamine, , pyridoxine , phosphates. small amount of vitamin b6 excreted in feces.