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November 06, 2016 00:02

Vitamin E : deficiency and hypervitaminosis

Vitamin E - a group of compounds (tocopherols and tocotrienols), which have similar biological effects.The most biologically active - alpha-tocopherol, but beta, gamma and theta-tocopherols and four tocotrienols more stereoisomers have also important biological activities.

These agents act as antioxidants to prevent peroxidation of polyunsaturated fatty acids in cell membranes.Plasma levels of tocopherol varies with the general level of plasma lipids (serum) blood.Typically, the plasma level of a-tocopherol - 5-20 micrograms / ml (11.6 46.4 mmol / l).Another controversy is the question of whether vitamin E protects against cardiovascular disease, Alzheimer's disease, tardive dyskinesias, prostate cancer in smokers.Although the amount of vitamin E in many fortified foods and supplements they estimated in ME, recommended to evaluate the use of mg or mmol.

Hypovitaminosis vitamin E

Deficiency of vitamin E in the diet is typical in developing countries;deficiency in adults in the developed world and

meets with rare usually due to lipid malabsorption.Main symptoms - hemolytic anemia and neurological disorders.Diagnosis is based on measuring the ratio of plasma a-tocopherol to the total plasma lipid;low ratio confirm deficiency of vitamin E. Treatment consists of oral administration of vitamin E in the presence of high doses of neurological symptoms, or in the case of vitamin E deficiency due to malabsorption.

vitamin E deficiency causes haemolysis of red blood cells and degeneration of neurons, especially the peripheral axons and neurons posterior pole.

Causes of vitamin E deficiency

In developing countries, the most common cause - inadequate intake of vitamin E. In developed countries, the most common causes - diseases that cause malabsorption of lipids, including abetalipoproteinemia (Besse Korntsveyga syndrome: congenital absence of apolipoprotein B), a chronic cholestaticdisease, hepatobiliary disease, pancreatitis, short bowel syndrome, cystic fibrosis.A rare genetic form of vitamin E deficiency without lipid malabsorption - a consequence of impaired liver metabolism.

Symptoms of vitamin E deficiency

main symptoms - mild hemolytic anemia and nonspecific neurologic manifestations.Abetalipoproteinemia leads to progressive neuropathy and retinopathy in the first two decades of life.

Deficiency of vitamin E contributes to retinopathy of prematurity (retinopathy of prematurity), and in some cases, the emergence of intraventricular and subepindemalnyh (subdural) hemorrhage in newborns.In these premature infants develop muscle weakness.

Children chronic cholestatic hepatobiliary pathology or cystic fibrosis cause neurological disorders, including spinal ataxia with loss of deep tendon reflexes, ataxia of the trunk and limbs, positional and vibratory sensory loss, ophthalmoplegia, muscle weakness, ptosis, and dysarthria.

Deficiency of vitamin E in adults with malabsorption rarely causes spinal ataxia, as they have large reserves of vitamin E in adipose tissue.

Diagnostics vitamin E

deficiency of vitamin E deficiency is unlikely, if history is no information about his lack of consumption or of provoking factors (conditions).usually required to determine the level of vitamin To confirm the diagnosis.Measuring the degree of hemolysis of red blood cells in response to the hydrogen peroxide can suggest a given diagnosis but is not specific.Hemolysis is amplified as vitamin E deficiency weakens the stability of erythrocytes.

The most direct method of diagnosis - measurement of alpha-tocopherol in the blood plasma.Adults can be suspected deficiency of vitamin E, tocopherol level if

level of a-tocopherol in the plasma of children and adults with abetalipoproteinemia usually not determined.

Prevention and treatment of vitamin E deficiency

preterm infants may require supplements of vitamin E, despite the fact that human milk and commercial infant formula contain a sufficient amount of vitamin E for infants who were born at term.

In those cases, when malabsorption is a clear clinical deficiency is assigned a-tocopherol at a dose of 15 to 25 mg / kg body weight into the 1 per day.Nevertheless, for the treatment of neuropathy in the early stages or overcome the consequences of defects of absorption and transport acanthocytosis when higher doses are used in injections.

Hypervitaminosis (intoxication) of vitamin E

Many adults take relatively large amounts of the vitamin (a-tocopherol - 400-800 mg / day) for many months and years without obvious indications.Sometimes develop muscle weakness, fatigue, nausea and diarrhea.The most significant risk - the risk of bleeding.However, the bleeding does not occur if the dose does not exceed 1000 mg / day or the patient takes oral coumarin or warfarin.Thus, the upper limit for adults over 19 years - 1000 mg (2326 mmol) for any form of alpha-tocopherol.In the recent reviews of previous studies reported that high doses of vitamin E may increase the risk of premature death.(Miller ER 3rd, Pastor-Barriuso R, Dalal D, Riemersma RA, Appel LJ, Guallar E. Meta-analysis: high-dosage vitamin E supplementation may increase all-cause mortality Ann Intern Med 2005; 142:. 37-46.[PubMed abstract]).