Fat-soluble vitamins Part II: Focus on vitamins E and K
The category of fat-soluble vitamins includes the representatives A, D, E and K. Vitamins A and D are probably the best-known representatives of their grouping and have consequently already been described and discussed in detail. In the following, we take a look at two other vitamins that should not be underestimated: Vitamin E and K.
The main characteristic of fat-soluble vitamins is so important that it should be recalled. Vitamins with fat-soluble properties are generally only absorbed during digestion in the presence of dietary fats. Subsequently, these substances are stored in the body in very individual places in order to be able to fall back on them when needed. In case of an overdose, an accumulation with toxic side effects can occur due to the storage quality.
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Vitamin E for cell protection and vitamin K for blood clotting
To build up some understanding of vitamins E and K, let’s first take a look at their chemical names. Vitamin E is called tocopherol and vitamin K is called phylloquinone (vitamin K1) and menaquinone (vitamin K2).
Vitamin E is known for its cell-protecting properties in our body. As a component of the cell membrane, vitamin E acts as an extremely effective antioxidant*. Consequently, this substance is able to protect the cell from free radicals and their damaging effects. As part of the radical defence, tocopherol itself is chemically modified. In order to once again perform the function of cell protection, vitamin E is regenerated by vitamin C.
When considering vitamin K, one first distinguishes between vitamin K1 and K2. Both forms are chemically derived from the so-called menadione. The difference between the two is that vitamin K1 is found in plants and vitamin K2 is synthesised by the body’s own intestinal bacteria. This vitamin is involved in activating the clotting factors found in the organism. In this respect, vitamin K plays an important role in the process of blood clotting.
Vitamin E and K sources: especially plant foods are recommended
Since vitamin E and K play very important roles in our body, it is essential to know the necessary daily amount to be taken. As is so often the case, a distinction is made between women and men as well as age when it comes to dosage. According to the German Nutrition Society, male adolescents and adults should consume between 70–80 micrograms of vitamin K and 12–15 milligrams of vitamin E daily. For females, the values for vitamin K are 60–65 micrograms daily and for vitamin E 11–12 milligrams daily. Vitamin K is found in almost all green vegetables (especially spinach), but is synthesised independently by our body’s intestinal bacteria anyway. Sources of vitamin E can only be plant-based; it is mainly found in vegetable oils and cereal germs.
Vitamin E and K deficiencies are extremely rare
In principle, it is important to ensure a sufficient supply of vitamins. But what are the consequences of a vitamin E and K deficiency? An acute vitamin E deficiency is rather rare. One of the reasons is that the body has very large stores of vitamin E. If a deficiency should occur, there is a risk that the body will be depleted. Should a deficiency occur, there is a risk of symptoms that arise due to oxidative stress. Consequently, the very effect of cell protection is missing, which can lead to oxidative damage to the cells. In such a case, a so-called haemolytic anaemia can occur. In this case, the erythrocytes disintegrate, resulting in anaemia.
Since vitamin K is often found in food and is also produced by the body’s own intestinal bacteria, a deficiency of this vitamin is also not very common. Exceptions are, for example, prolonged antibiotic therapy, which damages the intestinal flora to such an extent that a vitamin K deficiency can occur. The consequences of a deficiency would primarily be seen in blood clotting. Those affected often show an increased tendency to bleed.
Vitamin E and K: Hypervitaminosis is not to be feared
The consideration of possible overdoses, which always pose a danger with fat-soluble vitamins, plays a much smaller role with vitamins E and K. With vitamin E, no hypervitaminoses are to be feared. No hypervitaminoses are known with vitamin E, and too much vitamin K is extremely rare. If vitamin K is overdosed in individual cases, there is a risk of thrombosis, vomiting and anaemia.
Facts about vitamin E and K
1. Vitamin E protects our body cells by being incorporated into the cell membranes. It relies on the water-soluble vitamin C for reactivation.
2. Vitamin K activates selected clotting factors and thus plays an important role in the process of blood clotting
3. Male adults and adolescents should consume 70–80 micrograms of vitamin K and 12–15 milligrams of vitamin E daily.
4. Female adults and adolescents should consume 60–65 micrograms of vitamin K and 11–12 milligrams of vitamin E daily.
5. Vitamin K is found in green vegetables, but it is also produced by the body’s own intestinal bacteria.
6. Good sources of vitamin E are vegetable oils and cereal germs.
7. Vitamin E deficiency is very rare due to large depots in the body. A deficiency leads to oxidative cell damage in particular.
8. A vitamin K deficiency is very rare. It is often caused by destruction of the intestinal flora. In the case of such a deficiency, blood clotting is disturbed.
9. There are no known overdoses of vitamin E in humans. An overdose of vitamin K is also rare and, if it occurs, results in vomiting, thrombosis and anaemia.
* Antioxidant: Substances that protect the body and thus its own cells from oxidative stress. In particular, the defence against harmful forms of oxygen is in the foreground
Text sources:
(1) https://www.dge.de/wissenschaft/referenzwerte/vitamin-e/
(2) https://www.dge.de/wissenschaft/referenzwerte/vitamin-k/
(3) Königshoff and Brandenburger, Biochemistry, 4th edition, 2018.
(4) Horn, Biochemistry of Humans, 7th edition, 2018; Rassow et al, Biochemistry, 4th edition, 2016; Herdegen, Pharmacology and Toxicology, 4th edition, 2019.
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