Human Vitamin E Deficiency

Vitamin E deficiency is not a problem, even among people living on relatively poor diets. In depletion studies, very low intakes of vitamin E must be maintained for many months before there is any significant fall in circulating a-tocopherol, because there are relatively large tissue reserves of the vitamin.

Deficiency develops in patients with severe fat malabsorption, cystic fibro-sis, chronic cholestatic hepatobiliary disease, and in two rare groups of patients with genetic diseases:

1. Patients with congenital abetalipoproteinemia, who are unable to synthesize VLDL. This was the first condition reported that confirmed the essentiality of vitamin E in human beings (Muller et al., 1983). The patients have undetectably low plasma levels of a-tocopherol and develop devastating ataxic neuropathy and pigmentary retinopathy. The administration of massive oral supplements of vitamin E (of the order of 100 mg of a-tocopherol acetate per kg of body weight per day) halts the progression of the neuropathy in children diagnosed relatively late and can prevent the development of neuropathy altogether if therapy is started early enough (Muller, 1986).

2. Patients who lack the hepatic tocopherol transfer protein (Section 4.2) and suffer from what has been called AVED (ataxia with vitamin E deficiency) are unable to export a-tocopherol from the liver in VLDL.

In both groups of patients, the only source of vitamin E for peripheral tissues will be recently ingested vitamin E in chylomicrons. They develop cerebellar ataxia, axonal degeneration of sensory neurons, skeletal myopathy, and pigmented retinopathy similar to those seen in experimental animals.

In premature infants, whose reserves of the vitamin are inadequate, vitamin E deficiency causes a shortened half-life of erythrocytes, which can progress to increased intravascular hemolysis, and hence hemolytic anemia. In infants treated with hyperbaric oxygen, there is a risk of damage to the retina (retro-lental fibroplasia), and vitamin E supplements may be protective, although this is not firmly established (Phelps, 1987).

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