thiamin

chemical forms

thiamin (free form), TDP (active form), TTP, TMP

food sources thiamin

plant foods: free form thiamin

animal foods: TDP mostly. bit of TDP and TMP

supplement foods: thiamin mononitrate, thiamin hydrochloride

food sources: pork loin, salmon, pasta, noodles

factors influencing thiamin stability

methylene bridge- sensitive to sulfites, heat destruction (pH dependent), antithiamines (thiaminases, polyhydroxyphenols)

digestion absorption etc

digestion: free thiamin readily absorbed, TMP TTP TDP require dephosphorylation carried out by small intestines phosphatases

absorption: in duodenum and jejunum. free thiamin thru active transport thru thiamin transporters ThTr1 and ThTr2. passive diffusion at more than 2.5mg

transport:90% of circulating thiamin is in RBCs. facil diffusion into RBCs. uptake of thiamin thru active transport mostly by liver (ThTr2) and skeletal muscle (ThTr1). upon cellular intake, thiamin is phosphorylated to TDP

storage: skeletal muscles take up half of bodys total thiamin. half life 9-20 days

excretion: thiamin is excreted thru the kidney and then urinary excretion. occurs if bodys thiamin is above tissue needs and capacity

metabolic functions

nervous system. coenzyme for pyruvate to acetyl-coa, TCA cycle, hexose monophosphate shunt, bracnhed chain amino acid metabolism.

thiamin deficiency

oxidation of glucose is impaired

beri beri

weight loss, weakness, irregular heart rate, edema

dry beruberu: occurs in adults. wernicke encephalopathy - abnormla eye movment. can lead to korsakoff psychosis. most common w chronic alcoholism

risk factors for thiamin

lack of diverse food, reliance on low thiamin staples like white rice, some consumption of thiamin inhibitors

alcoholism, factors that increase thiamin needs (cancer/hiv etc)