Which of the following nutrients is absorbed in the jejunum?

The jejunum, which is the second part of the small intestine, plays a critical role in nutrient absorption. It is particularly well-suited for absorbing water-soluble vitamins, such as Vitamin C and the B-complex vitamins. These vitamins are typically absorbed through the mucosa of the jejunum via active transport and passive diffusion mechanisms.

Water-soluble vitamins do not require any specific transport molecules like fat-soluble vitamins do; they are readily absorbed into the bloodstream because the jejunal wall is lined with numerous microvilli that increase the surface area for absorption. Additionally, the environment in the jejunum is slightly more alkaline and optimally suited for the dissolution and absorption of these vitamins compared to other sections of the gastrointestinal tract.

While calcium and iron are also absorbed in the small intestine, calcium absorption primarily occurs in the duodenum and is regulated by vitamin D, while iron absorption takes place predominantly in the duodenum and proximal jejunum but may be influenced by dietary factors and the body's iron stores. Vitamin D, being a fat-soluble vitamin, is absorbed more effectively in the presence of dietary fats within the jejunum but primarily facilitates the absorption of calcium rather than being absorbed directly in large quantities.

Understanding the specific roles of different segments of