It is important to include foods high in vitamin E on a daily basis to get enough vitamin E from foods alone. Vegetable oils, nuts, green leafy vegetables, and fortified cereals are common food sources of vitamin E…Read more..
Vitamin E is a naturally occurring fat-soluble vitamin that exists in eight different forms: alpha-, beta-, gamma-, and delta tocopherol, and alpha-, beta-, gamma-, and delta-tocotrienol that have varying levels of biological activity. Alpha- (or a-) tocopherol appears to be the most active form, and is the only form that is recognized to meet human requirements. Serum concentrations of alpha-tocopherol depend on the liver, which takes up the nutrient after absorption of all the forms from the small intestine. The liver then preferentially secretes only alpha tocopherol, and metabolizes and excretes the other vitamin E forms. As a result, blood and cellular concentrations of other forms of vitamin E are lower than those of alpha-tocopherol and thus have been less studied.
Vitamin E has powerful antioxidant activities which protect cells from the damaging effects of free radicals. Free radicals combine with oxygen and form reactive oxygen species (ROS) that damage cells. Free radicals are produced endogenously when the body metabolizes food to energy. Exogenous sources come from exposure to cigarette smoke, air pollution, and ultraviolet radiation from the sun. ROS are part of signaling mechanisms among cells and antioxidant vitamin E protects the cells against free radical damage. Scientists are investigating whether, by limiting free-radical production and possibly through other mechanisms, vitamin E might help prevent or delay the chronic diseases associated with free radical’s. Besides functioning as an antioxidant, vitamin E is also involved in immune function and, as shown primarily by in vitro studies of cells, cell signaling, regulation of gene expression, and other metabolic processes .
Vitamin E in supplements is usually sold as a-tocopheryl acetate, a form of a-tocopherol that protects its ability to function as an antioxidant. The synthetic form is labeled dl, whereas the natural form is labeled d. The synthetic form is only half as active as the natural form. It is important to include foods high in vitamin E on a daily basis to get enough vitamin E from foods alone. Vegetable oils, nuts, green leafy vegetables, and fortified cereals are common food sources of vitamin E.
Recommendations for vitamin E are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB), Institute of Medicine (IOM), The National Academies (formerly National Academy of Sciences). DRI is the general term for a set of reference values used to plan and assess nutrient intakes of healthy people. These
values, which vary by age and gender, include:
- Recommended Dietary Allowance (RDA): average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy people.
- Adequate Intake (AI): established when evidence is insufficient to develop an RDA and is set at a level assumed to ensure nutritional adequacy.
- Tolerable Upper Intake Level (UL): maximum daily intake unlikely to cause adverse health effects. ULs for vitamin E are listed inside the cover of this text.
An Article by a Nutrition Student ‘Syeda Ruhina Raushan’