07/02/2026
Your gut: a 7-meter assembly line extracting every usable molecule with molecular specificity.
This figure maps how different sections of the gastrointestinal tract specialize in absorbing specific nutrients. From the stomach to the large intestine, each region has a defined biochemical role that determines how vitamins, minerals, fats, and amino acids enter the body.
1️⃣ Stomach – preparation and partial absorption
The stomach begins protein digestion through acid and enzymes while absorbing a few small molecules such as water, ethanol, and some minerals.
🟢 Example: Copper, iodide, and fluoride can pass directly through the stomach lining, but most nutrients remain bound until released in the small intestine.
2️⃣ Duodenum – the entry point for minerals and fat-soluble vitamins
As chyme from the stomach mixes with bile and pancreatic enzymes, the duodenum becomes the main site for mineral and fat-soluble vitamin absorption.
🟢 Example: Calcium, iron, magnesium, and vitamins A, D, E, and K are absorbed here, often requiring bile acids for solubility.
3️⃣ Jejunum – primary absorption zone for macronutrients
The jejunum’s extensive villi and microvilli surface area make it the key site for nutrient uptake.
🟢 Example: Lipids, monosaccharides, amino acids, and small peptides are efficiently absorbed, along with B vitamins such as thiamin, riboflavin, and niacin.
4️⃣ Ileum – absorption of specialized compounds and vitamins
The ileum completes digestion and reclaims nutrients not absorbed upstream.
🟢 Example: Vitamin B12 binds to intrinsic factor for absorption here, while bile salts and fat-soluble vitamins are recycled back to the liver.
5️⃣ Large intestine – water recovery and microbial synthesis
Although most nutrients are absorbed earlier, the colon plays a key role in fluid and electrolyte balance and produces additional vitamins through bacterial fermentation.
🟢 Example: Gut microbes synthesize vitamin K and biotin, while fermentation of fiber yields short-chain fatty acids that fuel colon cells.
Your gut is not a single absorption site but a coordinated system of specialized regions—each tuned to extract specific nutrients with precision, ensuring that every molecule from food is used efficiently to sustain life.
