Micronutrients: Where are Vitamins and Nutrients Absorbed?

Anne Kamiya, Donna Ricketts
  • Author
    Anne Kamiya

    Anne has experience in science research and writing. She has a graduate degree in nutrition (gut microbiome & nutritional microbiology) and undergraduate degrees in microbiology (immunology & medical microbiology) and English (myth & folklore). She has also worked as an ocean & Earth science educator.

  • Instructor
    Donna Ricketts

    Donna Ricketts is a health educator with 15 years of professional experience designing health and wellness programs for adults and children.

Learn about micronutrient absorption and understand the process of water absorption. Compare micronutrients and macronutrients and see where nutrients are absorbed. Updated: 03/04/2022

What Are Micronutrients?

All living creatures on earth, from the largest whale to the smallest bacteria need food to live. The reason food is important is because it contains nutrients that provide the biological parts cells need to create energy, repair themselves, and grow.

Nutrients needed in substantial amounts in the diet are called macronutrients. When a pepperoni pizza is eaten, the cheese, meats and added oils contain fats, the pepperoni and cheese toppings contain protein, the dough contains carbohydrates, and the soda that came with it contains water. Water, carbohydrates, proteins, and fats are the four macronutrients because large amounts of these are needed by the body each day. Macronutrients (except water) are used as building blocks and fuel and eventually turned into cellular energy.

Nutrients needed in miniscule amounts in the diet are called micronutrients. Although less of them are required, this does not mean they are less important. In fact, without micronutrients, a person would become ill and die. Micronutrients include vitamins which are categorized as either water-soluble vitamins or fat-soluble vitamins, and minerals which are categorized as either microminerals or trace minerals. Some examples of vitamins found in a pepperoni pizza are thiamine and vitamin B12. Some examples of minerals found in a pepperoni pizza are calcium and zinc. Micronutrients are not used as fuel, rather, they are more like tools the body needs to make fuel from macronutrients and to keep the body functioning. For example, some micronutrients are used as cofactors to help enzymes work properly. Other micronutrients are used as antioxidants to keep cells healthy.

Small Intestine Role

When the pizza is eaten, it first goes into the mouth, where mechanical chewing and saliva break down carbohydrates. When swallowed it goes down the esophagus and enters the stomach where stomach acid and protein-digesting enzymes start working on the proteins. Food then goes into the small intestine where the full process of digestion begins.

There are three sections of the small intestine. The first section called the duodenum starts after the stomach and is the shortest part of the small intestine (about one foot long). The second section, where most nutrients are absorbed, is the jejunum and about eight feet long. The last section of the small intestine is the ileum and the longest portion, about twelve feet long.

Although the small intestine might seem like it is a smooth and hollow tube, microscopically, it is not smooth at all. The surface of the small intestine is covered with shaggy, hair-like projections comparable to finger-like fibers of a shaggy carpet, called villi. The villi have villi of their own called microvilli. The reason the intestine needs villi and microvilli is because they increase the surface area of the small intestine by up to 600 times, creating an enormous area for absorbing nutrients.


An electron microscope view of small intestinal microvilli, which are the tiny shaggy protrusions that grow on the villi that line the small intestine. Villi and microvilli have been frequently compared to finger-like projections and kind of look like shaggy rug fibers.

Small intestine microvilli viewed with electron microscope.


What Are Micronutrients?

Your body absorbs two types of nutrients: macronutrients and micronutrients. Macronutrients (carbohydrates, proteins, and fats) are your body's direct source of fuel or energy, while micronutrients, which are commonly referred to as vitamins and minerals, are needed in minimal amounts. But, just because you only need a little doesn't mean that they don't pack a punch.

Micronutrients are vital for the proper functioning of all your body's systems. They include such minerals as iron, which helps your body produce red blood cells, and calcium, which aids with blood clotting. Micronutrients also include vitamins such as vitamin A (essential for vision health), while vitamin C is essential for healthy teeth, gums, and bones.

In addition, micronutrients indirectly serve as the catalyst to release the energy from the macronutrients. Without them, you couldn't get the energy out of carbohydrates and fats or convert the protein you eat into your own lean body mass. Unless vitamins and minerals are efficiently absorbed, none of the nutrients can function properly.

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  • 0:02 What Are Micronutrients?
  • 1:19 Role of the Small Intestine
  • 2:11 Micronutrient Absorption
  • 4:33 Water Absorption
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Where Are Nutrients Absorbed?

So, where are nutrients absorbed? Macronutrients are absorbed by the microvilli in the small intestine, but it is quite a journey to get there. When food is eaten, enzymes produced by the mouth, stomach, pancreas, liver, and small intestine digest food into its most microscopic components that can be absorbed into the intestinal cells. Fats become fatty acids, carbohydrates become sugars and oligosaccharides (short sugar chains), and proteins become amino acids. Cells in the human body, including small intestinal cells, are surrounded by a semi-permeable membrane which allows some molecules to enter without energy, while other molecules need help from a protein or may require energy from the cell. Cellular energy is a molecule called adenosine triphosphate (ATP).

Simple diffusion or passive diffusion:

Fatty acids get through the semi-permeable membrane of intestinal cells by passive or simple diffusion. This is a form of passive transport that does not need energy for a solute (which in this case is the fatty acid molecule) to move with the concentration gradient, from an area of high to low solute concentration.


In simple diffusion, particles move from an area where there are many particles to an area of few particles until equilibrium is reached. This process occurs naturally over time because the particles are moving with the concentration gradient.

An illustration showing the process of passive or simple diffusion.


Facilitated diffusion:

Sugars like fructose are absorbed by facilitated diffusion, which is a form of passive transport, and does not need energy to move into the semi-permeable membrane of intestinal cells. However, in facilitated diffusion, a solute (which in this case is fructose) moves from an area of high to low solute concentration with help of a transport protein. Like simple diffusion, the sugars are moving with the concentration gradient, so ATP is not required.


Facilitated diffusion requires a transport protein to get through the semi-permeable membrane of cells. This illustration depicts two kinds of transport proteins: carrier and channel proteins.

An illustration of the process of facilitated diffusion which needs transport proteins.


Active transport:

Amino acids cannot move through the semi-permeable membrane of intestinal cells without both a transporter protein and energy. Active transport is similar to facilitated transport where a transport protein is required to move a solute (which in this case is an amino acid) but it is different because the amino acid is moving from an area of low to high solute concentration, and ATP is always required. Because the amino acid molecule is moving against the concentration gradient, it needs help from a transport protein in the cell membrane and ATP to be moved from the outside of the cell to the inside of the cell.

Where Are Vitamins Absorbed?

So, where are vitamins absorbed? Earlier in the lesson it was said that vitamins are categorized as either water-soluble or fat-soluble. Although all vitamins are absorbed by the intestinal villi, solubility impacts absorption. Vitamin A, D, E, and K are fat-soluble and become surrounded by fatty acids in spherical structures called micelles. They are absorbed into lymphatic vessels. All the B vitamins, folic acid and vitamin C are water-soluble and are absorbed into the bloodstream.

Example of how a water-soluble vitamin is absorbed:

Orange juice has a lot of fruit sugar and vitamin C. When swallowing the juice, it goes down the esophagus into the stomach and then the small intestine. During this process, the orange juice is broken down into its most basic parts including vitamins and minerals. Vitamin C is absorbed through the semi-permeable membrane of the small intestinal villi cells by active transport. It is then taken into blood capillaries where it can be distributed throughout the bloodstream.

Example of how a fat-soluble vitamin is absorbed:

The Role of the Small Intestine

Micronutrients are released from food by digestion and then absorbed mainly in the small intestines. A little bit is absorbed in the stomach and large intestines, but mainly in the small intestines. The inside surface of the small intestine contains many folds covered by villi, very thin, long projections on the inside of the intestinal wall. These projections contain muscle, so they are constantly moving in a wave-like motion. Their purpose is to increase the absorption potential of the small intestine by increasing its surface size. On each villus are even tinier microvilli that are nutrient-specific; this is where absorption occurs.

Micronutrient Absorption

During the process of absorption, nutrients that come from the food (including carbohydrates, proteins, fats, vitamins, and minerals) pass through channels in the small intestine into the bloodstream. The blood works to distribute these nutrients to the rest of the body. There are two primary ways that nutrients cross through the walls of the small intestine and enter the bloodstream: passive diffusion and active transport absorption.

Passive diffusion can be thought of as pouring liquid through a cheesecloth. It's a simple process where nutrients move from an area of high concentration (like the inside of the intestine) to an area of low concentration (like the bloodstream). Active transport absorption means that the nutrient requires a helper, or carrier molecule, to get it through the intestinal wall into the bloodstream.

Some micronutrients are more inclined to one type of absorption than the other, but many vitamins, including fat-soluble ones (like A, D, E, and K) and water-soluble ones (like C and most of the Bs), are absorbed through passive diffusion. Fat-soluble vitamins must be transported with dietary fat into the lymphatic system and then into the bloodstream. If you don't eat enough dietary fat, your body will not properly absorb these vitamins. A very low-fat diet can lead to deficiencies of fat-soluble vitamins.

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Video Transcript

What Are Micronutrients?

Your body absorbs two types of nutrients: macronutrients and micronutrients. Macronutrients (carbohydrates, proteins, and fats) are your body's direct source of fuel or energy, while micronutrients, which are commonly referred to as vitamins and minerals, are needed in minimal amounts. But, just because you only need a little doesn't mean that they don't pack a punch.

Micronutrients are vital for the proper functioning of all your body's systems. They include such minerals as iron, which helps your body produce red blood cells, and calcium, which aids with blood clotting. Micronutrients also include vitamins such as vitamin A (essential for vision health), while vitamin C is essential for healthy teeth, gums, and bones.

In addition, micronutrients indirectly serve as the catalyst to release the energy from the macronutrients. Without them, you couldn't get the energy out of carbohydrates and fats or convert the protein you eat into your own lean body mass. Unless vitamins and minerals are efficiently absorbed, none of the nutrients can function properly.

The Role of the Small Intestine

Micronutrients are released from food by digestion and then absorbed mainly in the small intestines. A little bit is absorbed in the stomach and large intestines, but mainly in the small intestines. The inside surface of the small intestine contains many folds covered by villi, very thin, long projections on the inside of the intestinal wall. These projections contain muscle, so they are constantly moving in a wave-like motion. Their purpose is to increase the absorption potential of the small intestine by increasing its surface size. On each villus are even tinier microvilli that are nutrient-specific; this is where absorption occurs.

Micronutrient Absorption

During the process of absorption, nutrients that come from the food (including carbohydrates, proteins, fats, vitamins, and minerals) pass through channels in the small intestine into the bloodstream. The blood works to distribute these nutrients to the rest of the body. There are two primary ways that nutrients cross through the walls of the small intestine and enter the bloodstream: passive diffusion and active transport absorption.

Passive diffusion can be thought of as pouring liquid through a cheesecloth. It's a simple process where nutrients move from an area of high concentration (like the inside of the intestine) to an area of low concentration (like the bloodstream). Active transport absorption means that the nutrient requires a helper, or carrier molecule, to get it through the intestinal wall into the bloodstream.

Some micronutrients are more inclined to one type of absorption than the other, but many vitamins, including fat-soluble ones (like A, D, E, and K) and water-soluble ones (like C and most of the Bs), are absorbed through passive diffusion. Fat-soluble vitamins must be transported with dietary fat into the lymphatic system and then into the bloodstream. If you don't eat enough dietary fat, your body will not properly absorb these vitamins. A very low-fat diet can lead to deficiencies of fat-soluble vitamins.

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Frequently Asked Questions

Where are most vitamins absorbed in the digestive tract?

Vitamins and minerals are absorbed in the villi and microvilli of the small intestine. Most vitamins are absorbed in the central part of the small intestine called the jejunum.

Where is Vitamin C absorbed in the body?

Vitamin C, like other nutrients, is absorbed by the small intestinal villi and microvilli. The specific areas of the small intestine where vitamin C is absorbed is the jejunum and ileum, which are the middle and last sections of the small intestine.

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