Where are minerals absorbed in the small intestine?

December 8, 2025 •

2 min read

The small intestine absorbs approximately 90% of all nutrients ingested through our food. This highly efficient process ensures that essential minerals, vitamins, proteins, and carbohydrates are extracted from digested food and passed into the bloodstream to nourish the body. The small intestine's three distinct segments each play a unique role in this vital function.

Quick Summary

Minerals are absorbed across all three sections of the small intestine—the duodenum, jejunum, and ileum. Different minerals and absorption mechanisms are dominant in each section, influencing how the body obtains essential micronutrients from food.

Key Points

Location Matters: Different minerals, such as iron and calcium, are absorbed most efficiently in specific sections of the small intestine (duodenum, jejunum, or ileum).
Two Main Pathways: Minerals enter the body's circulation through both active transport, which requires energy, and passive diffusion, which relies on concentration gradients.
Specialized Transporters: Minerals like iron use specific protein channels (e.g., DMT1) to cross the intestinal wall, a process primarily occurring in the duodenum.
Regulated Absorption: The body can adjust its absorption of minerals like iron and calcium based on its current needs, increasing uptake during deficiency or periods of higher demand like pregnancy.
Inhibitory Substances: Compounds found in some foods, such as phytates and oxalates, can bind to minerals like calcium and zinc, reducing their bioavailability.
Vitamin D is a Cofactor: The absorption of calcium is highly dependent on sufficient levels of active vitamin D, which regulates the necessary transport mechanisms.
Mineral Competition: High levels of one mineral, such as zinc, can interfere with the absorption of another, like copper, due to competition for transport pathways.

The small intestine is the primary site for nutrient absorption. Its structure, including folds, villi, and microvilli, maximizes the surface area for this complex process, which involves both active transport and passive diffusion. The location of absorption varies depending on the specific mineral.

Mineral Absorption in the Duodenum

The duodenum, the first section of the small intestine, is the primary site for iron absorption, especially under acidic conditions. Active calcium absorption also occurs here, particularly when dietary intake is low. Copper and phosphate are also absorbed in this section.

Mineral Absorption in the Jejunum

The jejunum is where the majority of overall nutrient absorption takes place. This segment is a significant site for mineral uptake, especially when mineral intake is high, allowing for passive absorption. Calcium and magnesium are notably absorbed here.

Mineral Absorption in the Ileum

The ileum is the final section. Magnesium absorption continues here, and the terminal ileum is specialized for absorbing bile salts.

Factors Influencing Mineral Absorption

Several factors impact how well minerals are absorbed, including dietary antagonists like phytates and oxalates, competition between minerals for transporters, the body's mineral status, and medical conditions. Enhancers like vitamin D are also crucial.

Comparison of Mineral Absorption Sites in the Small Intestine


Mineral	Primary Absorption Site	Absorption Mechanism(s)	Influencing Factors
Iron	Duodenum	Active transport via DMT1	Acidic environment, competition from other minerals
Calcium	Duodenum & Jejunum (active); Ileum (passive)	Active transport (vitamin D-dependent) & passive diffusion	Vitamin D levels, phytates, oxalates, aging
Magnesium	Jejunum & Ileum	Passive paracellular & active transcellular transport	Dietary intake, fermentation activity in colon
Zinc	Duodenum & Jejunum	Active transport via Zip4, passive diffusion	Phytates, dietary fiber, competition from copper

Conclusion

The small intestine's sections specialize in absorbing different minerals. The duodenum is vital for active absorption of minerals like iron, while the jejunum and ileum are key for bulk and passive absorption of minerals like calcium and magnesium. Effective mineral absorption relies on a balanced diet, adequate vitamin D, and a healthy gut, highlighting the link between digestive health and overall well-being. More details on nutrient absorption can be found here: {Link: NIH https://www.ncbi.nlm.nih.gov/books/NBK597379/}.

Keypoints

Location Matters: Different minerals, such as iron and calcium, are absorbed most efficiently in specific sections of the small intestine (duodenum, jejunum, or ileum).

Frequently Asked Questions

The duodenum is the main site for absorbing iron. It is also where the active absorption of calcium occurs, a process regulated by vitamin D, along with smaller amounts of phosphate and copper.

Yes, the jejunum is where the bulk of mineral absorption takes place, including most calcium, magnesium, and zinc. The ileum primarily handles the reabsorption of bile salts and vitamin B12, but also continues to absorb minerals not fully taken up in the earlier segments, like magnesium.

Active absorption uses energy and specific transporter proteins to move minerals against a concentration gradient, as seen with iron in the duodenum. Passive absorption is the movement of minerals down their concentration gradient without requiring energy, a major route for minerals like calcium and magnesium, especially when intake is high.

Dietary components can significantly influence mineral absorption. Compounds called anti-nutrients, such as phytates and oxalates found in certain plants, can bind to minerals like zinc and calcium, hindering their absorption. Mineral competition can also occur when multiple minerals use the same transport pathways.

Yes, several medical conditions, including inflammatory bowel diseases like Crohn's disease and celiac disease, can damage the small intestine's lining. This damage can reduce the surface area and impair the specialized transport mechanisms needed for effective mineral absorption, potentially leading to deficiencies.

For some minerals, yes. For example, calcium absorption occurs through both active and passive pathways. When dietary intake is high, passive diffusion through the longer jejunum and ileum becomes a significant route. When intake is low, the body relies more on the vitamin D-regulated active transport in the duodenum.

The terminal ileum has specific receptors for the intrinsic factor-vitamin B12 complex and for bile salts. This specialization ensures that these particular substances are absorbed and recycled efficiently after most other nutrients have been absorbed in the earlier sections of the small intestine.