How Does the Body Get Nutrients from the Blood?

December 6, 2025 •

3 min read

According to the National Institutes of Health, the small intestine absorbs most of the nutrients in your food, which are then passed to the circulatory system to be used or stored. This intricate process is precisely how the body gets nutrients from the blood to power its countless functions, from energy production to cellular repair.

Quick Summary

This article explains the complex process by which cells receive nutrients from the bloodstream. It details how the digestive system breaks down food, how nutrients are absorbed into the blood via the small intestine, and how the circulatory system delivers these vital components to individual cells through capillaries for energy, growth, and repair.

Key Points

Absorption in the Small Intestine: Digested nutrients are absorbed primarily through the finger-like villi in the small intestine, which dramatically increase the surface area for uptake.
Dual Transport Routes: Water-soluble nutrients (like glucose and amino acids) enter blood capillaries, while fat-soluble nutrients (fats and certain vitamins) enter the lymphatic system via lacteals.
Hepatic Portal System: Water-soluble nutrients travel directly to the liver via the hepatic portal vein for processing and distribution.
The Capillary Network: Nutrients are ultimately delivered to individual cells via the thin-walled capillaries, where exchange occurs.
Cellular Exchange by Diffusion: At the cellular level, nutrients and oxygen diffuse out of the capillaries and into the cells, while waste products diffuse back into the blood.
Liver's Central Role: The liver plays a crucial role in managing nutrient levels, storing excess, and releasing it when needed to maintain a balanced blood composition.

The Journey of Nutrients: From Food to Bloodstream

Before the body can get nutrients from the blood, the food we eat must undergo a series of transformations within the digestive system. The process begins in the mouth, where mechanical chewing and salivary enzymes start breaking down carbohydrates. In the stomach, powerful acids and enzymes continue the breakdown, particularly for proteins. The journey culminates in the small intestine, where the bulk of chemical digestion and nutrient absorption occurs.

The Role of the Small Intestine

Within the small intestine, millions of tiny, finger-like projections called villi and microvilli dramatically increase the surface area available for absorption. Each villus is connected to a network of capillaries and a central lymph vessel known as a lacteal. This dual pathway is crucial for accommodating both water-soluble and fat-soluble nutrients.

Absorption of Water-Soluble Nutrients: Broken-down carbohydrates (as monosaccharides like glucose) and proteins (as amino acids) are absorbed into the capillaries of the villi.
Transportation via the Portal Vein: These nutrient-rich capillaries merge into the hepatic portal vein, which carries the blood directly to the liver.
Processing by the Liver: The liver acts as a central processing and sorting facility, where it processes, stores, and redistributes nutrients as needed to maintain a stable blood composition.

Transporting Fat-Soluble Nutrients

Fats, along with fat-soluble vitamins (A, D, E, K), take a different route. Because they are not water-soluble, they are first packaged into complexes called chylomicrons. These are too large to enter the blood capillaries directly and instead enter the lacteals within the villi. The lymphatic system then transports the chylomicrons, which eventually empty into large veins near the heart, mingling with the general bloodstream.

The Capillary Network: The Final Destination for Nutrients

After leaving the liver (for water-soluble nutrients) or the lymphatic system (for fats), the nutrient-rich blood is pumped by the heart throughout the body. The circulatory system branches into progressively smaller vessels until it reaches the capillaries, the body's smallest and most abundant blood vessels.

The Process of Cellular Exchange

Capillaries have extremely thin, semi-permeable walls that allow for the efficient exchange of substances between the blood and the surrounding tissue. The process of delivering nutrients from the blood to individual cells primarily involves diffusion, where substances move from an area of higher concentration to an area of lower concentration.

Here’s how the exchange happens:

Slowed Blood Flow: The narrow diameter of capillaries drastically reduces the speed of blood flow, providing ample time for exchange to occur.
Diffusion Across Capillary Walls: Oxygen, simple sugars, and amino acids diffuse out of the blood plasma, pass through the interstitial fluid (the fluid surrounding cells), and are taken up by the cells.
Waste Exchange: Simultaneously, cells release waste products, such as carbon dioxide and urea, which diffuse back into the bloodstream to be carried away for removal by the lungs and kidneys.

Comparison of Water-Soluble vs. Fat-Soluble Nutrient Transport


Feature	Water-Soluble Nutrients (e.g., Glucose, Amino Acids)	Fat-Soluble Nutrients (e.g., Vitamins A, D, E, K)
Initial Absorption	Absorbed directly into blood capillaries within the villi of the small intestine.	Absorbed into lacteals (lymph vessels) within the villi of the small intestine.
Immediate Transport Route	Travel via the hepatic portal vein directly to the liver.	Travel via the lymphatic system before entering general circulation near the heart.
Carrier Molecules	Typically travel dissolved directly in the blood plasma.	Packaged into chylomicrons for transport through the watery blood.
Processing Organ	The liver processes and stores excess glucose and amino acids.	Adipose (fat) tissue stores fat-soluble vitamins for long periods.

Conclusion

The journey of nutrients from a consumed meal to the individual cells of the body is a multi-step process orchestrated by the digestive and circulatory systems. After being broken down and absorbed, nutrients are segregated based on their solubility and transported via distinct routes. The vast capillary network serves as the critical site for exchange, where slowed blood flow and thin vessel walls allow essential nutrients and oxygen to diffuse into the surrounding tissues, fueling every cell and sustaining life itself. This constant, regulated delivery system ensures that the body's energy needs are met and cellular functions are maintained.

Frequently Asked Questions

The primary site for nutrient absorption is the small intestine, specifically through tiny, finger-like projections called villi that line its walls.

Fats are absorbed into the lymphatic system via special vessels called lacteals, whereas carbohydrates and proteins are absorbed directly into the blood capillaries.

The liver acts as a processing center for most absorbed nutrients, storing excess, converting them into other necessary substances, and distributing them to the rest of the body as needed.

Blood flow is slowed in capillaries because of their extremely narrow diameter. This allows sufficient time for the vital exchange of nutrients and oxygen with the surrounding tissues.

Waste products from cells, such as carbon dioxide and urea, diffuse back into the blood within the capillary network. The blood then carries these wastes to organs like the lungs and kidneys for removal.

Yes, the lymphatic system eventually empties into large veins near the heart, which is how absorbed fats and fat-soluble vitamins eventually enter the general circulation.

The body maintains a stable level of nutrients, or metabolic homeostasis, through organs like the liver, which stores excess nutrients like glucose and releases them into the bloodstream when levels are low.