Definition:

Vitamin E refers to a group of 8 naturally occurring compounds with antioxidant activity: alpha-, beta-, gamma-, and delta-tocopherol and alpha-, beta-, gamma-, and delta-tocotrienol.

• α-Tocopherol functions as a chain-breaking antioxidant, preventing the propagation of free radicals in membranes and plasma lipoproteins. α-Tocopherol is also likely involved in strengthening certain aspects of cell-mediated immunity.
• Vitamin E deficiency can be caused by fat malabsorption disorders or by genetic abnormalities that affect vitamin E transport. Severe deficiency symptoms include vitamin E deficiency-induced ataxia, peripheral neuropathy, muscle weakness, and damage to the retina of the eye.
• Randomized controlled trials investigating primary and/or secondary prevention of chronic diseases, such as cardiovascular disease, cancer, and cataracts, do not currently support a preventative effect of supplemental α-tocopherol.
• Limited clinical evidence suggests that vitamin E supplementation may be beneficial for managing age-related macular degeneration and fatty liver diseases secondary to type 2 diabetes mellitus
• Supplementation with α-tocopherol was found to slow cognitive decline or loss of functional abilities in cognitively impaired subjects in some, but not all, clinical studies.
• Plant seeds, especially sunflower seeds, almonds, and hazelnuts, are rich sources of α-tocopherol such that many vegetable oils (e.g., olive oil and canola oil) also contain α-tocopherol. Other sources include tomato, avocado, spinach, asparagus, Swiss chard, and broccoli.
• High doses of supplemental α-tocopherol may interfere with the vitamin K-dependent blood clotting cascade and increase the risk of bleeding in individuals taking anticoagulant drugs.

Dosage and administration

• The current recommended dietary allowance (RDA) is 15 mg/day of α-tocopherol. It is estimated that more than 90% of American adults do not meet the estimated average requirement (EAR) of 12 mg/day of α-tocopherol.
• The most commonly used dosages of vitamin E in clinical trials have been 100–800 IU/day, although dosages of 50–3,200 IU/day have been used in different studies.
• Dosage comparisons between alpha-tocopherol and mixed tocopherols are difficult because tocopherols other than alpha-tocopherol are not counted in determining the number of IU contained in a product.
• Vitamin E is best absorbed when taken with a meal that contains fat.