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food source · 1
←Pork
Pork is one of the richest common sources of thiamin (vitamin B1): lean pork has about 0.6–0.9 mg per 100 g, several times as much as beef. Thiamin sits in the lean meat, so a fatty cut such as belly dilutes it.
Mechanism · The pass glucose needs to be burned
Once rice and noodles are broken down into glucose, it has to get into the mitochondria before it can be burned for energy. In the body, thiamin is converted into thiamin pyrophosphate (TPP), the pass that gate requires; without enough of it, the sugar piles up outside. So when thiamin runs short, the first to suffer are the nerves and the heart, which burn the most energy and can least switch to other fuels; the numb hands and feet, swelling and heart failure of beriberi all start here.
Numbers · Lean pork and polished rice
Lean pork has about 0.6–0.9 mg of thiamin per 100 g, several times as much as beef. Thiamin sits in the lean, so choosing belly dilutes that whole list of micronutrients. In grains, thiamin is concentrated in the bran and germ, and polishing rice into white rice loses about 70–80% of it, which is why beriberi historically spread with polished white rice.
cofactor · 1
Three enzyme complexes, pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase and branched-chain keto acid dehydrogenase, all need both thiamin (B1) and lipoic acid: B1 cuts a carbon-carbon bond in the fuel molecule, and lipoic acid passes the removed piece on to the next step. Without either one, these steps stall.
depletes · 1
Long-term drinking makes the gut absorb thiamin (vitamin B1) poorly and depletes the body's stores, while its need for thiamin does not fall. The most serious result is Wernicke encephalopathy, with abnormal eye movements, unsteady walking and confusion, which can progress to Korsakoff syndrome. A long-term drinker with these symptoms needs emergency care right away; hospitals usually give B1 before giving glucose to such patients, so as not to set off an acute attack.