Vitamin E

Vitamin E is a fat soluble vitamin which includes a group of compounds with similar structure. The generic name for the group are tocopherols, where 8 natural compounds are divided into four tocopherols and four tocotrienols.

Considering the biological function of the different forms of tocopherols and tocotrienols is very important in clinical practice due to the differences in their bioavailability, bioactiveness and toxicity.

The most active form is RRR-alpha-tocopherol, i.e., d-alpha-tocopherol.

Which foods contain the vitamin?

• Wheat germ oil
• Soy oil
• Rapeseed oil
• Sunflower seed oil
• Almond
• Walnut
• Hazelnut
• Peanut
• Salmon
• Egg
• Carrot

Biological functions of the vitamin

Vitamin E is mainly an antioxidant. It is the most important lipophilic natural antioxidant in the human organism. Due to its lipophilic properties, vitamin E accumulates in biomembranes, blood lipoproteins and the cells of fat tissue, where it reacts with the reactive particles of oxygen — the antioxidative role of vitamin E is realised.

Vitamin E is also called the eliminator of the free radicals of oxygen. In this way, vitamin E inhibits the peroxidation of polyunsaturated fatty acids in the phospholipides of biomembranes and lipoproteins of blood. This is due to the fact that it controls the peroxidation of lipides and protects the structural-functional integrity of biomembranes and other structures.

Vitamin E also protects the unsaturated side chain of vitamin A from peroxidation, thus increasing the bioactivity of vitamin A and promoting its storage in the liver.

In antioxidant protective reaction, vitamin E mainly cooperates with ascorbic acid.

In addition to its antioxidative properties, it promotes the storage of selenium in the organism and the synthesis of heme. It decreases the synthesis of thromboxane and thus regulates the aggregation of thrombocytes. Vitamin E also participates in the functioning of the regulatory enzymes of the proliferation of smooth muscle cells, regulates the activity of protein kinase C and affects the synthesis of prostaglandins and leukotrienes, thus reducing inflammation.

Absorption, storage and excretion

Vitamin E is absorbed from the small intestine, supported by the secretion of pancreas and bile. Absoroption is inhibited by excess iron, drinking water rich in chlorines, mineral oils used as laxatives, oral contraceptives, antibiotics, abundance of polyunsaturated fatty acids in food, excess vitamin A in the gastrointestinal tract and damages of small intestine.

The vitamin is stored in liver, fat tissue and somewhat also in the cardiac muscle, adrenal gland, skeletal muscles and blood lipoproteins. The supplies last for about 1–4 months.

Vitamin E is excreted from the organism in the composition of bile, bound with glucuronic acid.

Problems resulting from deficiency

• Damages to the membranes of erythrocytes (haemolytic anaemia)
• Reduction in the synthesis of haemoglobin
• Spermatogenesis disorders
• Difficulties getting pregnant
• Muscular dystrophy
• Premature ageing

Risk groups for developing the deficiency

• Persons having problems with the digestion and absorption of lipides
• Users of oestrogens, i.e., the antagonists of vitamin E
• Patients with parenteral nutrition
• Patients with haemolytic anaemia
• People with damaged small intestine
• People with chronic pancreatitis
• In case of gastrectomy

Toxicity

The symptoms of toxicity include muscle weakness, diarrhoea and headache.

The symptoms of acute toxicity include stomatitis, creatineurea, hives, vitamin K metabolism disorders, vaginal bleeding and visual disturbances.

It is known that very large doses may further increase the high blood pressure and damage the cardiac muscle in case of its chronic rheumatic disease — in this case the use of vitamin E must be justified and controlled.

Use of vitamin preparations

Additional administration of vitamin E is necessary, if large amounts of polyunsaturated fatty acids are used.

As an additional treatment component, vitamin E can be used for treating vitamin anaemias, atherosclerosis, angina pectoris, myocardial infarction, blood vessel thrombosis, haemorrhoids, diabetes, stroke, varicose veins, osteoporosis, Parkinsonism, gallstones, cataract, cystic fibrosis, hyperthyroidism, prostatitis, nephritis, allergies, bronchitis, jaundice, arthritis, muscular dystrophy, skin ulcers, acne, gastritis, cancer and menstrual disorders.

Figure 1. Vitamin E: alpha-tocopherol