Fat-soluble vitamins are small but important bulwarks of the body: They protect cells from destruction, allow wounds to heal better, strengthen teeth and bones and keep mucous membranes healthy.
Just like the water-soluble vitamins , the body only needs small amounts of the fat-soluble vitamins. Nevertheless, they are also vital and fulfill important functions in the body. Therefore, with the exception of vitamin D, which the body can produce itself with the help of sunlight, they have to be ingested through food.
Fat soluble means that these vitamins do not dissolve in water, but instead need fat as a transport medium. Only then can the body use them at all.
Vitamin A is important for the eyes
Vitamin A (retinol) enables vision at dusk and – together with other components – also enables color vision. Vitamin A is part of rhodopsin, the visual pigment in the sensory cells of the retina. Vitamin A also keeps the skin and mucous membranes healthy, boosts sperm production and promotes the development of the embryo in the womb.
Pregnant and breastfeeding women have an increased need for vitamin A: They need up to 1.5 milligrams a day. Otherwise, about 0.8 to 1.0 milligrams per day, for example from animal foods such as liver or eggs, are sufficient. The body can also convert vegetable beta-carotene into vitamin A. A lack of vitamin A therefore rarely occurs. Beta-carotene is found in carrots, spinach, red peppers and dried apricots.
Vitamin D strengthens the bones
Vitamin D (calciferol) is important for bones and teeth because it ensures that calcium is absorbed from food. If there is a lack of calcium in the body , vitamin D draws the mineral from food more. That is known.
However, researchers suspect that the vitamin has many other effects. The role of vitamin D for health has been intensively researched in recent years, and not all questions have been answered. As things stand today, it has been shown that a good supply of vitamin D in the elderly can reduce the risk of falls, fractures and premature death.
Indispensable source: the sun
Vitamin D occupies a special position among the vitamins because humans do not only get it through food. In fact, humans produce a large part of their need for vitamin D, around 80 to 90 percent, themselves, in the skin. But that only works with enough sunlight.
How much vitamin D is produced by the skin depends on various factors: on the duration of the radiation, the area of the exposed skin, the skin color – dark-skinned people produce less vitamin D than light-skinned people.
Sunbathe unprotected? Yes, but only shortly
But something else is also decisive: the wavelength and the dose of UVB radiation. In the summer months it is possible to meet the demand – provided the sun is shining. Experts recommend exposing a quarter of the body surface, i.e. face, hands and parts of arms and legs, to the sun for a few minutes every day, at noon between 12 and 3 p.m. – uncovered and without sun protection, because the cream prevents the formation of vitamin D.
Depending on the skin type, this can range from a few minutes to a quarter of an hour in midsummer. It is always important that the skin does not suffer from sunburn! Before 12 p.m. and after 3 p.m. and outside the summer months, i.e. from March to May and from September, the recommended time in the sun is also extended because the radiation is then weaker.
Too little sun in the north
But the problem is: In northern latitudes, including Germany, the sun’s radiation in six months of the year does not have the necessary intensity to ensure a good supply of vitamin D. Researchers have established an estimate for this (50 nanomoles per liter in the blood). Food alone is also not enough. There are only a few foods that contain a significant amount of vitamin D anyway: oily fish such as salmon, herring and mackerel, otherwise liver, egg yolks, some edible mushrooms and margarine, which is often fortified with vitamin D.
In the months with little sunshine, the German Nutrition Society therefore recommends taking a vitamin D supplement to meet your needs. This is especially true for seniors aged 65 and over.
Vitamin E strengthens the immune system
Vitamin E (tocopherols) protects body cells. It protects the cell membranes from the damaging effects of destructive substances, so-called free radicals, and therefore possibly prevents cancer and arteriosclerosis. It strengthens the immune system and reduces inflammation.
A lot of vitamin E is mainly contained in vegetable oils, but also in wheat germ, nuts and avocados. The daily requirement of an adult of twelve to 15 milligrams can be covered well with food. Deficiency or excess are rare.
Vitamin K is involved in blood clotting
Vitamin K is involved in blood clotting and bone metabolism, among other things. If it is absent, bleeding will be more frequent and the blood will take longer to clot. However, there is seldom a deficiency in healthy people, because vitamin K is found in many foods, both vegetable and animal.
Good sources of vitamin K are spinach, chives, sauerkraut, flower, rose, red and kale as well as meat and cereal products. Although a large amount of vitamin K is also formed in the intestines, it is not clear to what extent this will help to meet the needs.
People with chronic liver disease or gastrointestinal diseases are susceptible to a vitamin K deficiency. The supply of vitamin K in infants is also problematic. They only have a small supply and cannot produce the substance sufficiently because their intestinal flora is not yet fully developed. Breast milk also contains too little of it. This is why newborns are sometimes prescribed an extra portion of vitamin K by the doctor.