Where does 90% of absorption occur in the intestine?

The jejunum and ileum are responsible for about 90% of nutrient absorption in the intestine. The jejunum, which is the middle section of the small intestine, is specifically designed for the absorption of carbohydrates, proteins, and fats. Its lining has numerous villi and microvilli, which dramatically increase the surface area to optimize nutrient uptake.

Following the jejunum, the ileum continues this function and is vital for absorbing specific vitamins and bile acids, further contributing to the overall absorptive capacity of the small intestine. The structural adaptations of these sections enable efficient utilization of digested nutrients, making them crucial for proper nutrition and energy supply to the body.

In contrast, the duodenum, while playing a key role in the initial stages of digestion by neutralizing stomach acid and mixing chyme with digestive enzymes, is not the primary site for nutrient absorption. Likewise, the cecum and colon primarily function in the absorption of water and electrolytes, as well as housing beneficial gut bacteria, but they are not involved in the major nutrient absorption that occurs in the jejunum and ileum. This distinction highlights the specialized roles of different sections of the intestine in the digestive process.