Micronutrient absorption – how vitamins and minerals are used by the body

In order for vitamins and minerals to be used by the body, they must first be absorbed in the digestive tract. This process mostly takes place in the small intestine. Only then do the micronutrients become available to the body to use.

What happens to micronutrients after eating.

After eating, the digestive system starts breaking down the food. This process begins in the mouth, where the food is broken into smaller pieces by chewing and mixed with saliva. In the gastrointestinal tract, stomach acid and digestive enzymes help to release micronutrients from the food and prepare them for absorption into the body.

Where does the absorption take place?

The small intestine is the main site for the absorption of micronutrients. The lining of the small intestine has a very large surface area and consists of cells with specialised mechanisms for transporting substances into the body. Only then can the body make use of the ingested micronutrients.

Different nutrients are transported via different routes. Some enter the body directly through the intestinal wall, while others are carried along specific transport proteins.

Difference between fat-soluble and water-soluble vitamins

How vitamins are absorbed depends on whether they are water- or fat-soluble

Fat-soluble vitamins

The fat-soluble vitamins (A, D, E and K) are absorbed during fat digestion, which is why fat in food is important for their good availability. The body can store fat-soluble vitamins, especially in the liver and adipose tissue. As a result, they remain available over a longer period of time.

Water-soluble vitamins

Water-soluble vitamins (B vitamins and vitamin C) are also absorbed in the intestine once they are released, and then enter the bloodstream. Unlike fat-soluble vitamins, they can be stored in the body only in limited amounts. Unneeded absorbed portions are usually excreted in the urine. One notable exception is vitamin B12, which can be stored in the liver.

The absorption of minerals

Minerals and trace elements are also mostly absorbed in the small intestine. They include, for example, calcium, magnesium and potassium (minerals) as well as iron, zinc, selenium and iodine (trace elements). How well they are absorbed depends on a number of factors, which are explained in more detail below.

Bioavailability of nutrients clearly explained

Bioavailability describes how much of a nutrient can actually be absorbed and used by the body.

This means that even if a food or dietary supplement contains a certain amount of a nutrient, not all of it is used by the body. Some of the nutrients supplied are always excreted in the form they were ingested, either because they were not absorbed or because they were not used. Bioavailability depends on various factors.

Factors that influence bioavailability.

Micronutrient absorption is a complex process that is influenced by various factors.

The composition of the meal plays an important role. Certain nutrients may increase or decrease the absorption of other nutrients. For example, dietary fats are important for the absorption of fat-soluble vitamins (A, D, E and K), and vitamin C promotes iron absorption. Certain plant substances, on the other hand, have a negative effect on the absorption of trace elements such as iron and zinc because they bind them. Typical examples are phytates (e.g. in whole grains, pulses) or certain polyphenols (tannins, e.g. from tea, coffee, cocoa).

Saliva, stomach acid and digestive enzymes help to release nutrients from food and ready them for absorption in the small intestine.

Special transport mechanisms and proteins in the intestinal wall enable the targeted transport of many vitamins and minerals from the intestine into the body. Their capacity is an important factor.

Health of the digestive system: well-functioning intestinal activity and an intact intestinal mucosa are also important for efficient nutrient absorption.

Transport and distribution in the body

Frequently asked questions about micronutrient absorption

Why is absorption as important as intake?

A good supply of micronutrients depends not only on how much is ingested through food, but also on the amount of nutrients that is actually passed on to the body.

An adequate intake therefore does not automatically guarantee an optimal supply. Only when micronutrients are successfully absorbed in the intestine, transported to the body and made use of there can they perform their important metabolic functions.

Therefore, in addition to the quality and composition of the diet, the many supporting digestive mechanisms and intestinal health play key roles in ensuring a good micronutrient supply.

You can find out which micronutrients are available and what functions they perform in the body in the overview article Micronutrients – Basics and Meaning for Health.

Can I expect my body to fully absorb all micronutrients from food?

No. Often, the proportion absorbed is even relatively small – but this is normal. The efficiency of nutrient intake depends on a number of factors, such as the composition of the meal, how your digestive system works, how well you are already being supplied and in what form you ingest the respective nutrients. For this reason, a varied diet consisting of high-quality foods that are processed as little as possible and good intestinal health are important prerequisites for the best possible care.

^{Vitamin C, zinc and selenium contribute to the normal functioning of the immune system.}

^{Magnesium and calcium contribute to maintaining normal bones.}

^{Vitamin B12 contributes to the normal functioning of the nervous system.}

^{Vitamins C, E, B2 as well as zinc, manganese and selenium help to protect cells from oxidative stress}