Vitamins: Types, Functions, and Recommended Requirements at a Glance

Vitamins are an essential part of nutrition – and at the same time a topic that raises many questions. What vitamins are there, what does your body need them for, and how much is sensible? In this overview, you will receive a scientifically based classification of vitamins, their functions, and individual needs.

What are vitamins?

Vitamins are essential micronutrients, that the human body needs for a variety of fundamental functions. Chemically, they are organic, low-molecular compounds that are involved in numerous metabolic processes. These include, among others, energy production, the normal function of the immune system, blood clotting, cell division, as well as processes related to protection against oxidative stress .

Unlike macronutrients such as carbohydrates, fats, and proteins, vitamins do not provide energy in the form of calories. Their role is different: they primarily act as cofactors, regulators, or protective substances and enable biochemical reactions in the body to proceed smoothly. Without vitamins, many of these processes would not function or would function only to a limited extent.

The human body cannot produce most vitamins or cannot produce them in sufficient quantities. Therefore, a regular intake through diet is necessary. Scientific literature describes that a long-term deficiency can be associated with functional impairments and typical deficiency symptoms. At the same time, it is true that an excessive intake – especially of fat-soluble vitamins such as A, D, E, and K – can be associated with undesirable effects. It is therefore not "much" that is crucial, but a needs-based and balanced supply.

However, vitamin is not the same as vitamin. Which ones exist and how they differ is shown in the next overview

What vitamins are there? – Overview of all vitamins and their functions

Vitamins are diverse – and none are alike. The following table provides a compact overview of all vitamins, their solubility, and the functions they can contribute to in the body.

** The mentioned functions correspond to approved health claims according to EU Regulation (EC) No.1924/2006.

Difference between fat-soluble and water-soluble vitamins

Vitamins can be fundamentally divided into fat-soluble and water-soluble vitamins. This distinction describes how vitamins are absorbed, transported, and stored in the body.

Fat-soluble vitamins (A, D, E, and K) are absorbed along with dietary fats. They can be stored in the body – primarily in the liver and adipose tissue. Regular intake is important, while excessive consumption should be avoided, as these vitamins can accumulate in the body (especially in adipose tissue or selected organs such as the liver).

Water-soluble vitamins (Vitamin C and the B vitamins) dissolve in water and are only stored to a limited extent. Excess amounts are usually excreted through metabolism. Particularly noteworthy is Vitamin B2 (Riboflavin), which leads to bright yellow urine in large amounts. Therefore, a continuous supply through diet is particularly relevant.

This distinction helps to better classify the role of individual vitamins and understand their supply in everyday life.

Which vitamins does the body need?

We now know how important vitamins are. But how many vitamins does the body actually need? The individual requirement can vary and depends on factors such as age, gender, diet, lifestyle, and special life phases. For orientation, the German Society for Nutrition (DGE) publishes scientifically based reference values for daily vitamin intake for healthy adults. The following table shows the recommended daily intakes for adults.In many situations, the recommended daily amount is not sufficient, resulting in an increased need.

Vitamins and dietary supplements – a classification

Vitamins are among the nutrients that are often discussed in everyday life – and about which many questions remain unanswered.

In principle, vitamins are absorbed through diet and are an essential part of a balanced nutrient supply. Many foods provide relevant amounts of individual vitamins – fresh fruits and vegetables such as citrus fruits or bell peppers are well-known sources of vitamin C.

However, in everyday life, it becomes evident that this supply is not always sufficient. For certain vitamins, an inadequate intake is reported in specific population groups. A commonly cited example is vitamin D: In Central Europe, the body's own production during the winter months (from October to April) is limited due to low sun exposure, which is why a low vitamin D status is often observed during this time.

The individual need also plays a role.In special life situations – such as during growth, pregnancy, or restricted food intake – the need for certain vitamins may be increased. In such cases, the scientific discussion considers the supplementary intake of individual vitamins.

Whether dietary supplements are sensible cannot be said universally. The crucial factor is your individual need – and this can best be assessed based on data. You can determine your vitamin D status, for example, through a medical blood test or a vitamin D test (home lab test). Based on this, a needs-based supplementation is possible, always as a supplement and not as a substitute for a balanced diet.

Vitamin preparations are available in different forms.The form that makes sense in each individual case depends, among other things, on the properties of the respective vitamin – such as its solubility, stability, and the method of absorption in the body.

Fat-soluble vitamins like vitamin D are often offered in oil-based form , for example as Vitamin D3K2 drops or as capsules with MCT oil. Vitamin D is sometimes found in combination with vitamin K, as both are fat-soluble and can be processed together in appropriate preparations. Vitamin K is also important for calcium homeostasis in the body - especially with increased vitamin D intake.

Water-soluble vitamins, particularly the B vitamins, are often offered as combination preparations such as a Vitamin B complex. Other vitamins, such as vitamin C, are available in various forms, including Vitamin C capsules , tablets, effervescent tablets, or powder.

Which form of administration is chosen is primarily a question of individual preference, tolerance, and application in everyday life

Conclusion – Understanding vitamins instead of supplementing indiscriminately

Vitamins are essential micronutrients with a variety of functions in the body. The amount of vitamins needed depends on individual requirements. Factors such as diet, lifestyle, and special life phases play a central role. Reference values like those of the DGE provide helpful guidance but do not replace personal assessment. Dietary supplements can only be meaningfully evaluated in the context of one's own needs. Therefore, it is not about providing as much as possible, but about consciously understanding vitamins and integrating them appropriately into one's own health strategy – informed, data-driven, and individualized.