They are easy to buy and are now available in all drugstores: food supplements.
In all shapes and sizes, the packs line up one after the other on the shelf, whether it is one for trace elements or vitamins. Those who take vitamin tablets in addition are usually considered very healthy - or at least health-conscious. But time and again the question comes up whether you need these tablets at all. Are people who eat a balanced diet not supplied with enough vitamins? Or does this only apply to people who hardly ever leave the house?

The term "vitamins" has been known to most people since childhood, mainly because our parents often pointed out their importance. Especially vitamin C and vitamin A came up very often in this "instruction". Maybe not in the way that the vitamins were called by their names, but when we ate carrots we were told how good they were for our eyes. The same goes for oranges and how good they are for the immune system.

But not all vitamins are the same. In fact, they are divided into two contrasting groups. Namely into...

- the water-soluble vitamins
and 

- the fat-soluble vitamins

To prevent the list from becoming too long, we will first introduce you to the fat-soluble vitamins in this article, as their number is manageable. In the following, you will be introduced to the tasks of the fat-soluble vitamins, what the human body needs them for and what the consequences of an overdose can be. But first, a few basic facts:

- Vitamins are micronutrients

- Vitamins are essential for the human body

- They are absorbed through food

- Fat-soluble vitamins are absorbed via the intestine 

The role of vitamin A in the body is possibly the best known of the four fat-soluble vitamins, because as a child you have probably heard the phrase "vitamin A is good for your eyes" or better said "carrots are good for your eyes". This vitamin is actually responsible for our eyesight as it is one of the important components of colour vision and helps us see in the dark. Apart from the eyes, vitamin A is also very important for the skin, bones and teeth. In addition, vitamin A plays an important role in reproduction as it is essential for testosterone production and foetal development. This vitamin is mainly stored in the liver.

Occurrence (in animal foods): butter, egg, cheese, fish and liver.

Beta-carotene, a precursor of vitamin A, is usually found in intensively coloured foods. In order for the beta-carotene to be completely converted into vitamin A in the body, it is important to eat these foods with fat. The best example of this is carrots. Carrots have a high beta-carotene content, but in order for this to be converted, carrots should not be eaten raw, but instead sautéed in a pan with a little oil so that it can fully develop.

Occurrence of beta-carotene: carrots, tomatoes, peppers, spinach, kale.

The recommended daily intake for adults is 1.0mg for men and 0.8mg for women.

An excess of vitamin A manifests itself as headaches, nausea or vomiting and can be harmful to the liver in the long run. Especially during pregnancy, an overdose should be avoided - if not deliberately avoided - as it can be dangerous for the unborn child.

Also known as the "sun vitamin". It is the only fat-soluble vitamin that can be produced by the body itself - through exposure to UV rays. Put simply, sunlight stimulates vitamin D production in our bodies. However, even the sun does not completely cover our vitamin D needs, which is why we have to get the micronutrient from food. Some countries with only a few sunny days a year (Scandinavia) are the best example of insufficient vitamin D intake from the sun.

The most important function of vitamin D is its involvement in bone metabolism. Vitamin D promotes the absorption of calcium and phosphate from the intestine and their incorporation into the bones. Furthermore, it promotes the immune defence and contributes to the inhibition of inflammation. For this reason, it is not uncommon for people with osteoporosis (bone loss) to be prescribed vitamin D tablets by their doctor.

Occurrence in food: Fish (salmon, herring, tuna), eggs, mushrooms, avocado, dark chocolate.

In this case, the German Nutrition Society (DGE) recommends a daily intake of about 200 micrograms.

An overdose of vitamin D can manifest itself as increased calcium levels, nausea, loss of appetite, abdominal cramps or even vomiting. In severe cases, kidney damage and cardiac arrhythmias can also occur. The website of the Robert Koch Institute even lists death as a consequence of vitamin D overdose. Since an overdose due to the body's own vitamin D production is rather unlikely, intoxication with vitamin D in this case would also be due to taking too high a dose of supplements.

Vitamin E has the ability to defuse free radicals through its antioxidant effect. Free radicals are aggressive oxygen compounds (the chain reactions of these form oxidative stress) that are created by normal metabolic reactions and damage our cells. Accordingly, vitamin E protects many areas in our body and additionally strengthens them. These include the heart, the skin, our cells and consequently our general immune system. In addition, vitamin E helps to protect against UV rays and counteracts inflammatory processes and hardening of the arteries. Vitamin E is often also an ingredient in skin and sun creams, as it gives the products a longer shelf life.

The recommended daily dose is 11-12mg for women and 12-15mg for men.

Occurrence: Vegetable oils (olive, sunflower and wheat germ oil), nuts, almonds, blackcurrants, sweet potatoes, peppers, avocado, linseed, pine nuts.

As a rule, an excess of vitamin E is not possible through intake from food alone. When this happens, it is usually the result of too much food supplementation, which manifests itself in the form of gastrointestinal complaints.

This fat-soluble vitamin is especially important for blood clotting. Without the supply of this vitamin, our body could not stop bleeding. It is absorbed in the intestine and transported to the liver via the blood. Its other tasks include preventing calcium deposits in the blood vessels and cartilage, controlling cell processes and slowing down bone loss in post-menopausal women.

The daily requirement of vitamin K depends on the individual's age and gender. For adults, it is roughly measured at 60-80 micrograms.

Occurrence: especially green vegetables and herbs are good vitamin K suppliers. These include broccoli, Brussels sprouts, kale, chives, avocado and celery.

According to current knowledge, an excess of vitamin K is not dangerous for adults. For newborns, however, it is a different story, because in them an overdose can cause the red blood cells to disintegrate.

Vitamin K deficiency can, for example, lead to spontaneous bleeding or excessive blood loss in case of injury, as it affects the coagulation system. Newborns always have a vitamin K deficiency at birth, which is why it is common in Germany for babies to receive additional vitamin K immediately after birth.

Basically, we can assume that we consume enough fat-soluble vitamins through a varied diet, so that supplements are not necessary. Furthermore, they are normally not necessary because our body does not need a large amount of them per day. This is made clear by the umbrella term vitamins, because the word 'micro' in micronutrient originally comes from the Greek and means 'small' - i.e. a small amount. 

A deficiency is possible when the absorption in the intestine is disturbed. For example, this occurs more frequently in people with chronic inflammatory bowel diseases (e.g. Crohn's disease). But other influences that can damage our intestinal health can also cause a vitamin deficiency.

Two examples are alcoholism and the use of certain medicines, primarily antibiotics.

Apart from our gut health, deficiencies also depend on how much fat we eat. Vitamins E, D, K and A rely on fat to be processed in the body. For this reason, a low-fat diet can be another factor in deficiency.

In order to avoid overdosing, it is essential to discuss with your doctor whether taking supplements is necessary at all. Especially in the case of vitamin A and D, this can have serious damaging consequences.