The term vitamin E covers eight related fat-soluble compounds found in nature: four tocopherols (alpha-, beta-, gamma-, and delta-) and four tocotrienols (alpha-, beta-, gamma-, and delta-). In humans, only alpha-tocopherol is specifically selected and enriched by the liver and is therefore the most abundant in the human body (1). The other vitamin E forms are rapidly metabolized and are present at much lower concentrations. Therefore, the Food and Nutrition Board recommended in 2000 to establish recommended intakes of vitamin E based on alpha-tocopherol (2).

 

The form of alpha-tocopherol found in plants is RRR-alpha-tocopherol (also referred to as natural or d-alpha-tocopherol). The vitamin E form mainly used in fortified foods and dietary supplements is all-rac-alpha-tocopherol (synthetic or dl-alpha-tocopherol). It contains RRR-alpha-tocopherol and seven highly similar alpha-tocopherol forms. All-rac-alpha-tocopherol is defined to be slightly less biologically active than RRR-alpha-tocopherol (~26% less); a revision of this definition is currently being discussed.

 

Vitamin E deficiency does not manifest itself as prominently as ‘scurvy’ (vitamin C deficiency) or ‘rickets’ (vitamin D deficiency). However, rare inherited disorders that result in vitamin E deficiency have been described. Untreated, these disorders can lead to nerve damage, muscle weakness, loss of ability to walk or blindness.