Benoist, Caroline C et al
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What Happens When You Eat Meat Timeline After Eating Meat (e.g., 100g beef containing ~2-3 mcg B12) Hour 0: You Eat the Meat B12 is bound to proteins in the meat Enters stomach Hour 0-2: Stomach Processing Stomach acid and pepsin release B12 from protein B12 binds to R-proteins (haptocorrin) secreted in saliva and stomach This B12-R-protein complex is acid-stable Moves to the small intestine Hour 2-4: Small Intestine Absorption Pancreatic enzymes degrade R-protein Intrinsic factor (from the stomach) binds to free B12 B12-intrinsic factor complex travels to the terminal ileum Absorption occurs in the terminal ileum via specific receptors KEY POINT: This process takes 4-8 hours minimum absorption is NOT immediate Hour 4-8: Absorption into Blood B12-intrinsic factor complex binds to cubilin receptors in the ileum B12 crosses the intestinal wall Enters portal circulation Goes to the liver first (first-pass through the liver) Hour 8-24: Liver Processing and Distribution The liver takes up much of the absorbed B12 Binds to transcobalamin II (active carrier) and haptocorrin (storage carrier) Released slowly into systemic circulation Peak serum B12 levels: 8-24 hours post-meal (not immediate!) EXPERIMENTAL SCENARIO: Testing Before and After Meat Scenario 1: Test Immediately After Eating Timeline: T = 0: Baseline B12 test drawn Result: 300 pg/mL T = 10 minutes: Eat a large steak (200g, ~5 mcg B12) T = 30 minutes: Retest B12 Expected Result: No significant change Still ~300 pg/mL Why
Common Reasons for Getting a B12 Injection Deficiency Treatment: Many people turn to B12 shots because they have been diagnosed with a deficiency due to poor dietary intake (common in vegetarians and vegans) or malabsorption issues
Dont worry about remembering those names just know that if youve got these variants (and theres a good chance you do), your standard B12 shot might be like trying to fill a bucket with holes in it
Giving yourself B12 injections at home is easier and more convenient than having your doctor do it every time, but doing the first injection can be a little unnerving for most folks
